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valgrind

Name
     valgrind - a suite of tools for debugging and profiling
     programs

Synopsis
     valgrind [valgrind-options] [your-program]
              [your-program-options]

Description
     Valgrind is a flexible program for debugging and profiling
     Linux executables. It consists of a core, which provides a
     synthetic CPU in software, and a series of debugging and
     profiling tools. The architecture is modular, so that new
     tools can be created easily and without disturbing the
     existing structure.

     Some of the options described below work with all Valgrind
     tools, and some only work with a few or one. The section
     MEMCHECK OPTIONS and those below it describe tool-specific
     options.

     This manual page covers only basic usage and options. For
     more comprehensive information, please see the HTML
     documentation on your system:
     $INSTALL/share/doc/valgrind/html/index.html, or online:
     http://www.valgrind.org/docs/manual/index.html.

Tool Selection Options
     The single most important option.

     --tool=<toolname> [default: memcheck]
         Run the Valgrind tool called toolname, e.g. memcheck,
         cachegrind, callgrind, helgrind, drd, massif, lackey,
         none, exp-sgcheck, exp-bbv, exp-dhat, etc.

Basic Options
     These options work with all tools.

     -h --help
         Show help for all options, both for the core and for the
         selected tool. If the option is repeated it is
         equivalent to giving --help-debug.

     --help-debug
         Same as --help, but also lists debugging options which
         usually are only of use to Valgrind's developers.

     --version
         Show the version number of the Valgrind core. Tools can
         have their own version numbers. There is a scheme in
         place to ensure that tools only execute when the core
         version is one they are known to work with. This was
         done to minimise the chances of strange problems arising
         from tool-vs-core version incompatibilities.

     -q, --quiet
         Run silently, and only print error messages. Useful if
         you are running regression tests or have some other
         automated test machinery.

     -v, --verbose
         Be more verbose. Gives extra information on various
         aspects of your program, such as: the shared objects
         loaded, the suppressions used, the progress of the
         instrumentation and execution engines, and warnings
         about unusual behaviour. Repeating the option increases
         the verbosity level.

     --trace-children=<yes|no> [default: no]
         When enabled, Valgrind will trace into sub-processes
         initiated via the exec system call. This is necessary
         for multi-process programs.

         Note that Valgrind does trace into the child of a fork
         (it would be difficult not to, since fork makes an
         identical copy of a process), so this option is arguably
         badly named. However, most children of fork calls
         immediately call exec anyway.

     --trace-children-skip=patt1,patt2,...
         This option only has an effect when --trace-children=yes
         is specified. It allows for some children to be skipped.
         The option takes a comma separated list of patterns for
         the names of child executables that Valgrind should not
         trace into. Patterns may include the metacharacters ?
         and *, which have the usual meaning.

         This can be useful for pruning uninteresting branches
         from a tree of processes being run on Valgrind. But you
         should be careful when using it. When Valgrind skips
         tracing into an executable, it doesn't just skip tracing
         that executable, it also skips tracing any of that
         executable's child processes. In other words, the flag
         doesn't merely cause tracing to stop at the specified
         executables -- it skips tracing of entire process
         subtrees rooted at any of the specified executables.

     --trace-children-skip-by-arg=patt1,patt2,...
         This is the same as --trace-children-skip, with one
         difference: the decision as to whether to trace into a
         child process is made by examining the arguments to the
         child process, rather than the name of its executable.

     --child-silent-after-fork=<yes|no> [default: no]
         When enabled, Valgrind will not show any debugging or
         logging output for the child process resulting from a
         fork call. This can make the output less confusing
         (although more misleading) when dealing with processes
         that create children. It is particularly useful in
         conjunction with --trace-children=. Use of this option
         is also strongly recommended if you are requesting XML
         output (--xml=yes), since otherwise the XML from child
         and parent may become mixed up, which usually makes it
         useless.

     --vgdb=<no|yes|full> [default: yes]
         Valgrind will provide "gdbserver" functionality when
         --vgdb=yes or --vgdb=full is specified. This allows an
         external GNU GDB debugger to control and debug your
         program when it runs on Valgrind.  --vgdb=full incurs
         significant performance overheads, but provides more
         precise breakpoints and watchpoints. See Debugging your
         program using Valgrind's gdbserver and GDB for a
         detailed description.

         If the embedded gdbserver is enabled but no gdb is
         currently being used, the vgdb command line utility can
         send "monitor commands" to Valgrind from a shell. The
         Valgrind core provides a set of Valgrind monitor
         commands. A tool can optionally provide tool specific
         monitor commands, which are documented in the tool
         specific chapter.

     --vgdb-error=<number> [default: 999999999]
         Use this option when the Valgrind gdbserver is enabled
         with --vgdb=yes or --vgdb=full. Tools that report errors
         will wait for "number" errors to be reported before
         freezing the program and waiting for you to connect with
         GDB. It follows that a value of zero will cause the
         gdbserver to be started before your program is executed.
         This is typically used to insert GDB breakpoints before
         execution, and also works with tools that do not report
         errors, such as Massif.

     --vgdb-stop-at=<set> [default: none]
         Use this option when the Valgrind gdbserver is enabled
         with --vgdb=yes or --vgdb=full. The Valgrind gdbserver
         will be invoked for each error after --vgdb-error have
         been reported. You can additionally ask the Valgrind
         gdbserver to be invoked for other events, specified in
         one of the following ways:

         *   a comma separated list of one or more of startup
             exit valgrindabexit.

             The values startup exit valgrindabexit respectively
             indicate to invoke gdbserver before your program is
             executed, after the last instruction of your
             program, on Valgrind abnormal exit (e.g. internal
             error, out of memory, ...).

             Note:  startup and --vgdb-error=0 will both cause
             Valgrind gdbserver to be invoked before your program
             is executed. The --vgdb-error=0 will in addition
             cause your program to stop on all subsequent errors.

         *   all to specify the complete set. It is equivalent to
             --vgdb-stop-at=startup,exit,valgrindabexit.

         *   none for the empty set.

     --track-fds=<yes|no> [default: no]
         When enabled, Valgrind will print out a list of open
         file descriptors on exit or on request, via the
         gdbserver monitor command v.info open_fds. Along with
         each file descriptor is printed a stack backtrace of
         where the file was opened and any details relating to
         the file descriptor such as the file name or socket
         details.

     --time-stamp=<yes|no> [default: no]
         When enabled, each message is preceded with an
         indication of the elapsed wallclock time since startup,
         expressed as days, hours, minutes, seconds and
         milliseconds.

     --log-fd=<number> [default: 2, stderr]
         Specifies that Valgrind should send all of its messages
         to the specified file descriptor. The default, 2, is the
         standard error channel (stderr). Note that this may
         interfere with the client's own use of stderr, as
         Valgrind's output will be interleaved with any output
         that the client sends to stderr.

     --log-file=<filename>
         Specifies that Valgrind should send all of its messages
         to the specified file. If the file name is empty, it
         causes an abort. There are three special format
         specifiers that can be used in the file name.

         %p is replaced with the current process ID. This is very
         useful for program that invoke multiple processes.
         WARNING: If you use --trace-children=yes and your
         program invokes multiple processes OR your program forks
         without calling exec afterwards, and you don't use this
         specifier (or the %q specifier below), the Valgrind
         output from all those processes will go into one file,
         possibly jumbled up, and possibly incomplete. Note: If
         the program forks and calls exec afterwards, Valgrind
         output of the child from the period between fork and
         exec will be lost. Fortunately this gap is really tiny
         for most programs; and modern programs use posix_spawn
         anyway.

         %n is replaced with a file sequence number unique for
         this process. This is useful for processes that produces
         several files from the same filename template.

         %q{FOO} is replaced with the contents of the environment
         variable FOO. If the {FOO} part is malformed, it causes
         an abort. This specifier is rarely needed, but very
         useful in certain circumstances (eg. when running MPI
         programs). The idea is that you specify a variable which
         will be set differently for each process in the job, for
         example BPROC_RANK or whatever is applicable in your MPI
         setup. If the named environment variable is not set, it
         causes an abort. Note that in some shells, the { and }
         characters may need to be escaped with a backslash.

         %% is replaced with %.

         If an % is followed by any other character, it causes an
         abort.

         If the file name specifies a relative file name, it is
         put in the program's initial working directory: this is
         the current directory when the program started its
         execution after the fork or after the exec. If it
         specifies an absolute file name (ie. starts with `/')
         then it is put there.

     --log-socket=<ip-address:port-number>
         Specifies that Valgrind should send all of its messages
         to the specified port at the specified IP address. The
         port may be omitted, in which case port 1500 is used. If
         a connection cannot be made to the specified socket,
         Valgrind falls back to writing output to the standard
         error (stderr). This option is intended to be used in
         conjunction with the valgrind-listener program. For
         further details, see the commentary in the manual.

Error-related Options
     These options are used by all tools that can report errors,
     e.g. Memcheck, but not Cachegrind.

     --xml=<yes|no> [default: no]
         When enabled, the important parts of the output (e.g.
         tool error messages) will be in XML format rather than
         plain text. Furthermore, the XML output will be sent to
         a different output channel than the plain text output.
         Therefore, you also must use one of --xml-fd, --xml-file
         or --xml-socket to specify where the XML is to be sent.

         Less important messages will still be printed in plain
         text, but because the XML output and plain text output
         are sent to different output channels (the destination
         of the plain text output is still controlled by
         --log-fd, --log-file and --log-socket) this should not
         cause problems.

         This option is aimed at making life easier for tools
         that consume Valgrind's output as input, such as GUI
         front ends. Currently this option works with Memcheck,
         Helgrind, DRD and SGcheck. The output format is
         specified in the file
         docs/internals/xml-output-protocol4.txt in the source
         tree for Valgrind 3.5.0 or later.

         The recommended options for a GUI to pass, when
         requesting XML output, are:  --xml=yes to enable XML
         output, --xml-file to send the XML output to a
         (presumably GUI-selected) file, --log-file to send the
         plain text output to a second GUI-selected file,
         --child-silent-after-fork=yes, and -q to restrict the
         plain text output to critical error messages created by
         Valgrind itself. For example, failure to read a
         specified suppressions file counts as a critical error
         message. In this way, for a successful run the text
         output file will be empty. But if it isn't empty, then
         it will contain important information which the GUI user
         should be made aware of.

     --xml-fd=<number> [default: -1, disabled]
         Specifies that Valgrind should send its XML output to
         the specified file descriptor. It must be used in
         conjunction with --xml=yes.

     --xml-file=<filename>
         Specifies that Valgrind should send its XML output to
         the specified file. It must be used in conjunction with
         --xml=yes. Any %p or %q sequences appearing in the
         filename are expanded in exactly the same way as they
         are for --log-file. See the description of --log-file
         for details.

     --xml-socket=<ip-address:port-number>
         Specifies that Valgrind should send its XML output the
         specified port at the specified IP address. It must be
         used in conjunction with --xml=yes. The form of the
         argument is the same as that used by --log-socket. See
         the description of --log-socket for further details.

     --xml-user-comment=<string>
         Embeds an extra user comment string at the start of the
         XML output. Only works when --xml=yes is specified;
         ignored otherwise.

     --demangle=<yes|no> [default: yes]
         Enable/disable automatic demangling (decoding) of C++
         names. Enabled by default. When enabled, Valgrind will
         attempt to translate encoded C++ names back to something
         approaching the original. The demangler handles symbols
         mangled by g++ versions 2.X, 3.X and 4.X.

         An important fact about demangling is that function
         names mentioned in suppressions files should be in their
         mangled form. Valgrind does not demangle function names
         when searching for applicable suppressions, because to
         do otherwise would make suppression file contents
         dependent on the state of Valgrind's demangling
         machinery, and also slow down suppression matching.

     --num-callers=<number> [default: 12]
         Specifies the maximum number of entries shown in stack
         traces that identify program locations. Note that errors
         are commoned up using only the top four function
         locations (the place in the current function, and that
         of its three immediate callers). So this doesn't affect
         the total number of errors reported.

         The maximum value for this is 500. Note that higher
         settings will make Valgrind run a bit more slowly and
         take a bit more memory, but can be useful when working
         with programs with deeply-nested call chains.

     --unw-stack-scan-thresh=<number> [default: 0] ,
     --unw-stack-scan-frames=<number> [default: 5]
         Stack-scanning support is available only on ARM targets.

         These flags enable and control stack unwinding by stack
         scanning. When the normal stack unwinding mechanisms --
         usage of Dwarf CFI records, and frame-pointer following
         -- fail, stack scanning may be able to recover a stack
         trace.

         Note that stack scanning is an imprecise, heuristic
         mechanism that may give very misleading results, or none
         at all. It should be used only in emergencies, when
         normal unwinding fails, and it is important to
         nevertheless have stack traces.

         Stack scanning is a simple technique: the unwinder reads
         words from the stack, and tries to guess which of them
         might be return addresses, by checking to see if they
         point just after ARM or Thumb call instructions. If so,
         the word is added to the backtrace.

         The main danger occurs when a function call returns,
         leaving its return address exposed, and a new function
         is called, but the new function does not overwrite the
         old address. The result of this is that the backtrace
         may contain entries for functions which have already
         returned, and so be very confusing.

         A second limitation of this implementation is that it
         will scan only the page (4KB, normally) containing the
         starting stack pointer. If the stack frames are large,
         this may result in only a few (or not even any) being
         present in the trace. Also, if you are unlucky and have
         an initial stack pointer near the end of its containing
         page, the scan may miss all interesting frames.

         By default stack scanning is disabled. The normal use
         case is to ask for it when a stack trace would otherwise
         be very short. So, to enable it, use
         --unw-stack-scan-thresh=number. This requests Valgrind
         to try using stack scanning to "extend" stack traces
         which contain fewer than number frames.

         If stack scanning does take place, it will only generate
         at most the number of frames specified by
         --unw-stack-scan-frames. Typically, stack scanning
         generates so many garbage entries that this value is set
         to a low value (5) by default. In no case will a stack
         trace larger than the value specified by --num-callers
         be created.

     --error-limit=<yes|no> [default: yes]
         When enabled, Valgrind stops reporting errors after
         10,000,000 in total, or 1,000 different ones, have been
         seen. This is to stop the error tracking machinery from
         becoming a huge performance overhead in programs with
         many errors.

     --error-exitcode=<number> [default: 0]
         Specifies an alternative exit code to return if Valgrind
         reported any errors in the run. When set to the default
         value (zero), the return value from Valgrind will always
         be the return value of the process being simulated. When
         set to a nonzero value, that value is returned instead,
         if Valgrind detects any errors. This is useful for using
         Valgrind as part of an automated test suite, since it
         makes it easy to detect test cases for which Valgrind
         has reported errors, just by inspecting return codes.

     --error-markers=<begin>,<end> [default: none]
         When errors are output as plain text (i.e. XML not
         used), --error-markers instructs to output a line
         containing the begin (end) string before (after) each
         error.

         Such marker lines facilitate searching for errors and/or
         extracting errors in an output file that contain
         valgrind errors mixed with the program output.

         Note that empty markers are accepted. So, only using a
         begin (or an end) marker is possible.

     --sigill-diagnostics=<yes|no> [default: yes]
         Enable/disable printing of illegal instruction
         diagnostics. Enabled by default, but defaults to
         disabled when --quiet is given. The default can always
         be explicitly overridden by giving this option.

         When enabled, a warning message will be printed, along
         with some diagnostics, whenever an instruction is
         encountered that Valgrind cannot decode or translate,
         before the program is given a SIGILL signal. Often an
         illegal instruction indicates a bug in the program or
         missing support for the particular instruction in
         Valgrind. But some programs do deliberately try to
         execute an instruction that might be missing and trap
         the SIGILL signal to detect processor features. Using
         this flag makes it possible to avoid the diagnostic
         output that you would otherwise get in such cases.

     --show-below-main=<yes|no> [default: no]
         By default, stack traces for errors do not show any
         functions that appear beneath main because most of the
         time it's uninteresting C library stuff and/or
         gobbledygook. Alternatively, if main is not present in
         the stack trace, stack traces will not show any
         functions below main-like functions such as glibc's
         __libc_start_main. Furthermore, if main-like functions
         are present in the trace, they are normalised as (below
         main), in order to make the output more deterministic.

         If this option is enabled, all stack trace entries will
         be shown and main-like functions will not be normalised.

     --fullpath-after=<string> [default: don't show source paths]
         By default Valgrind only shows the filenames in stack
         traces, but not full paths to source files. When using
         Valgrind in large projects where the sources reside in
         multiple different directories, this can be
         inconvenient.  --fullpath-after provides a flexible
         solution to this problem. When this option is present,
         the path to each source file is shown, with the
         following all-important caveat: if string is found in
         the path, then the path up to and including string is
         omitted, else the path is shown unmodified. Note that
         string is not required to be a prefix of the path.

         For example, consider a file named
         /home/janedoe/blah/src/foo/bar/xyzzy.c. Specifying
         --fullpath-after=/home/janedoe/blah/src/ will cause
         Valgrind to show the name as foo/bar/xyzzy.c.

         Because the string is not required to be a prefix,
         --fullpath-after=src/ will produce the same output. This
         is useful when the path contains arbitrary
         machine-generated characters. For example, the path
         /my/build/dir/C32A1B47/blah/src/foo/xyzzy can be pruned
         to foo/xyzzy using --fullpath-after=/blah/src/.

         If you simply want to see the full path, just specify an
         empty string:  --fullpath-after=. This isn't a special
         case, merely a logical consequence of the above rules.

         Finally, you can use --fullpath-after multiple times.
         Any appearance of it causes Valgrind to switch to
         producing full paths and applying the above filtering
         rule. Each produced path is compared against all the
         --fullpath-after-specified strings, in the order
         specified. The first string to match causes the path to
         be truncated as described above. If none match, the full
         path is shown. This facilitates chopping off prefixes
         when the sources are drawn from a number of unrelated
         directories.

     --extra-debuginfo-path=<path> [default: undefined and
     unused]
         By default Valgrind searches in several well-known paths
         for debug objects, such as /usr/lib/debug/.

         However, there may be scenarios where you may wish to
         put debug objects at an arbitrary location, such as
         external storage when running Valgrind on a mobile
         device with limited local storage. Another example might
         be a situation where you do not have permission to
         install debug object packages on the system where you
         are running Valgrind.

         In these scenarios, you may provide an absolute path as
         an extra, final place for Valgrind to search for debug
         objects by specifying
         --extra-debuginfo-path=/path/to/debug/objects. The given
         path will be prepended to the absolute path name of the
         searched-for object. For example, if Valgrind is looking
         for the debuginfo for /w/x/y/zz.so and
         --extra-debuginfo-path=/a/b/c is specified, it will look
         for a debug object at /a/b/c/w/x/y/zz.so.

         This flag should only be specified once. If it is
         specified multiple times, only the last instance is
         honoured.

     --debuginfo-server=ipaddr:port [default: undefined and
     unused]
         This is a new, experimental, feature introduced in
         version 3.9.0.

         In some scenarios it may be convenient to read debuginfo
         from objects stored on a different machine. With this
         flag, Valgrind will query a debuginfo server running on
         ipaddr and listening on port port, if it cannot find the
         debuginfo object in the local filesystem.

         The debuginfo server must accept TCP connections on port
         port. The debuginfo server is contained in the source
         file auxprogs/valgrind-di-server.c. It will only serve
         from the directory it is started in.  port defaults to
         1500 in both client and server if not specified.

         If Valgrind looks for the debuginfo for /w/x/y/zz.so by
         using the debuginfo server, it will strip the pathname
         components and merely request zz.so on the server. That
         in turn will look only in its current working directory
         for a matching debuginfo object.

         The debuginfo data is transmitted in small fragments (8
         KB) as requested by Valgrind. Each block is compressed
         using LZO to reduce transmission time. The
         implementation has been tuned for best performance over
         a single-stage 802.11g (WiFi) network link.

         Note that checks for matching primary vs debug objects,
         using GNU debuglink CRC scheme, are performed even when
         using the debuginfo server. To disable such checking,
         you need to also specify
         --allow-mismatched-debuginfo=yes.

         By default the Valgrind build system will build
         valgrind-di-server for the target platform, which is
         almost certainly not what you want. So far we have been
         unable to find out how to get automake/autoconf to build
         it for the build platform. If you want to use it, you
         will have to recompile it by hand using the command
         shown at the top of auxprogs/valgrind-di-server.c.

     --allow-mismatched-debuginfo=no|yes [no]
         When reading debuginfo from separate debuginfo objects,
         Valgrind will by default check that the main and
         debuginfo objects match, using the GNU debuglink
         mechanism. This guarantees that it does not read
         debuginfo from out of date debuginfo objects, and also
         ensures that Valgrind can't crash as a result of
         mismatches.

         This check can be overridden using
         --allow-mismatched-debuginfo=yes. This may be useful
         when the debuginfo and main objects have not been split
         in the proper way. Be careful when using this, though:
         it disables all consistency checking, and Valgrind has
         been observed to crash when the main and debuginfo
         objects don't match.

     --suppressions=<filename> [default:
     $PREFIX/lib/valgrind/default.supp]
         Specifies an extra file from which to read descriptions
         of errors to suppress. You may use up to 100 extra
         suppression files.

     --gen-suppressions=<yes|no|all> [default: no]
         When set to yes, Valgrind will pause after every error
         shown and print the line:

                 ---- Print suppression ? --- [Return/N/n/Y/y/C/c] ----

         Pressing Ret, or N Ret or n Ret, causes Valgrind
         continue execution without printing a suppression for
         this error.

         Pressing Y Ret or y Ret causes Valgrind to write a
         suppression for this error. You can then cut and paste
         it into a suppression file if you don't want to hear
         about the error in the future.

         When set to all, Valgrind will print a suppression for
         every reported error, without querying the user.

         This option is particularly useful with C++ programs, as
         it prints out the suppressions with mangled names, as
         required.

         Note that the suppressions printed are as specific as
         possible. You may want to common up similar ones, by
         adding wildcards to function names, and by using
         frame-level wildcards. The wildcarding facilities are
         powerful yet flexible, and with a bit of careful
         editing, you may be able to suppress a whole family of
         related errors with only a few suppressions.

         Sometimes two different errors are suppressed by the
         same suppression, in which case Valgrind will output the
         suppression more than once, but you only need to have
         one copy in your suppression file (but having more than
         one won't cause problems). Also, the suppression name is
         given as <insert a suppression name here>; the name
         doesn't really matter, it's only used with the -v option
         which prints out all used suppression records.

     --input-fd=<number> [default: 0, stdin]
         When using --gen-suppressions=yes, Valgrind will stop so
         as to read keyboard input from you when each error
         occurs. By default it reads from the standard input
         (stdin), which is problematic for programs which close
         stdin. This option allows you to specify an alternative
         file descriptor from which to read input.

     --dsymutil=no|yes [yes]
         This option is only relevant when running Valgrind on
         Mac OS X.

         Mac OS X uses a deferred debug information (debuginfo)
         linking scheme. When object files containing debuginfo
         are linked into a .dylib or an executable, the debuginfo
         is not copied into the final file. Instead, the
         debuginfo must be linked manually by running dsymutil, a
         system-provided utility, on the executable or .dylib.
         The resulting combined debuginfo is placed in a
         directory alongside the executable or .dylib, but with
         the extension .dSYM.

         With --dsymutil=no, Valgrind will detect cases where the
         .dSYM directory is either missing, or is present but
         does not appear to match the associated executable or
         .dylib, most likely because it is out of date. In these
         cases, Valgrind will print a warning message but take no
         further action.

         With --dsymutil=yes, Valgrind will, in such cases,
         automatically run dsymutil as necessary to bring the
         debuginfo up to date. For all practical purposes, if you
         always use --dsymutil=yes, then there is never any need
         to run dsymutil manually or as part of your
         applications's build system, since Valgrind will run it
         as necessary.

         Valgrind will not attempt to run dsymutil on any
         executable or library in /usr/, /bin/, /sbin/, /opt/,
         /sw/, /System/, /Library/ or /Applications/ since
         dsymutil will always fail in such situations. It fails
         both because the debuginfo for such pre-installed system
         components is not available anywhere, and also because
         it would require write privileges in those directories.

         Be careful when using --dsymutil=yes, since it will
         cause pre-existing .dSYM directories to be silently
         deleted and re-created. Also note that dsymutil is quite
         slow, sometimes excessively so.

     --max-stackframe=<number> [default: 2000000]
         The maximum size of a stack frame. If the stack pointer
         moves by more than this amount then Valgrind will assume
         that the program is switching to a different stack.

         You may need to use this option if your program has
         large stack-allocated arrays. Valgrind keeps track of
         your program's stack pointer. If it changes by more than
         the threshold amount, Valgrind assumes your program is
         switching to a different stack, and Memcheck behaves
         differently than it would for a stack pointer change
         smaller than the threshold. Usually this heuristic works
         well. However, if your program allocates large
         structures on the stack, this heuristic will be fooled,
         and Memcheck will subsequently report large numbers of
         invalid stack accesses. This option allows you to change
         the threshold to a different value.

         You should only consider use of this option if
         Valgrind's debug output directs you to do so. In that
         case it will tell you the new threshold you should
         specify.

         In general, allocating large structures on the stack is
         a bad idea, because you can easily run out of stack
         space, especially on systems with limited memory or
         which expect to support large numbers of threads each
         with a small stack, and also because the error checking
         performed by Memcheck is more effective for
         heap-allocated data than for stack-allocated data. If
         you have to use this option, you may wish to consider
         rewriting your code to allocate on the heap rather than
         on the stack.

     --main-stacksize=<number> [default: use current `ulimit'
     value]
         Specifies the size of the main thread's stack.

         To simplify its memory management, Valgrind reserves all
         required space for the main thread's stack at startup.
         That means it needs to know the required stack size at
         startup.

         By default, Valgrind uses the current "ulimit" value for
         the stack size, or 16 MB, whichever is lower. In many
         cases this gives a stack size in the range 8 to 16 MB,
         which almost never overflows for most applications.

         If you need a larger total stack size, use
         --main-stacksize to specify it. Only set it as high as
         you need, since reserving far more space than you need
         (that is, hundreds of megabytes more than you need)
         constrains Valgrind's memory allocators and may reduce
         the total amount of memory that Valgrind can use. This
         is only really of significance on 32-bit machines.

         On Linux, you may request a stack of size up to 2GB.
         Valgrind will stop with a diagnostic message if the
         stack cannot be allocated.

         --main-stacksize only affects the stack size for the
         program's initial thread. It has no bearing on the size
         of thread stacks, as Valgrind does not allocate those.

         You may need to use both --main-stacksize and
         --max-stackframe together. It is important to understand
         that --main-stacksize sets the maximum total stack size,
         whilst --max-stackframe specifies the largest size of
         any one stack frame. You will have to work out the
         --main-stacksize value for yourself (usually, if your
         applications segfaults). But Valgrind will tell you the
         needed --max-stackframe size, if necessary.

         As discussed further in the description of
         --max-stackframe, a requirement for a large stack is a
         sign of potential portability problems. You are best
         advised to place all large data in heap-allocated
         memory.

     --max-threads=<number> [default: 500]
         By default, Valgrind can handle to up to 500 threads.
         Occasionally, that number is too small. Use this option
         to provide a different limit. E.g.  --max-threads=3000.

Malloc()-related Options
     For tools that use their own version of malloc (e.g.
     Memcheck, Massif, Helgrind, DRD), the following options
     apply.

     --alignment=<number> [default: 8 or 16, depending on the
     platform]
         By default Valgrind's malloc, realloc, etc, return a
         block whose starting address is 8-byte aligned or
         16-byte aligned (the value depends on the platform and
         matches the platform default). This option allows you to
         specify a different alignment. The supplied value must
         be greater than or equal to the default, less than or
         equal to 4096, and must be a power of two.

     --redzone-size=<number> [default: depends on the tool]
         Valgrind's malloc, realloc, etc, add padding blocks
         before and after each heap block allocated by the
         program being run. Such padding blocks are called
         redzones. The default value for the redzone size depends
         on the tool. For example, Memcheck adds and protects a
         minimum of 16 bytes before and after each block
         allocated by the client. This allows it to detect block
         underruns or overruns of up to 16 bytes.

         Increasing the redzone size makes it possible to detect
         overruns of larger distances, but increases the amount
         of memory used by Valgrind. Decreasing the redzone size
         will reduce the memory needed by Valgrind but also
         reduces the chances of detecting over/underruns, so is
         not recommended.

     --xtree-memory=none|allocs|full [none]
         Tools replacing Valgrind's malloc, realloc, etc, can
         optionally produce an execution tree detailing which
         piece of code is responsible for heap memory usage. See
         ???  for a detailed explanation about execution trees.

         When set to none, no memory execution tree is produced.

         When set to allocs, the memory execution tree gives the
         current number of allocated bytes and the current number
         of allocated blocks.

         When set to full, the memory execution tree gives 6
         different measurements : the current number of allocated
         bytes and blocks (same values as for allocs), the total
         number of allocated bytes and blocks, the total number
         of freed bytes and blocks.

         Note that the overhead in cpu and memory to produce an
         xtree depends on the tool. The overhead in cpu is small
         for the value allocs, as the information needed to
         produce this report is maintained in any case by the
         tool. For massif and helgrind, specifying full implies
         to capture a stack trace for each free operation, while
         normally these tools only capture an allocation stack
         trace. For memcheck, the cpu overhead for the value full
         is small, as this can only be used in combination with
         --keep-stacktraces=alloc-and-free or
         --keep-stacktraces=alloc-then-free, which already
         records a stack trace for each free operation. The
         memory overhead varies between 5 and 10 words per unique
         stacktrace in the xtree, plus the memory needed to
         record the stack trace for the free operations, if
         needed specifically for the xtree.

     --xtree-memory-file=<filename> [default: xtmemory.kcg.%p]
         Specifies that Valgrind should produce the xtree memory
         report in the specified file. Any %p or %q sequences
         appearing in the filename are expanded in exactly the
         same way as they are for --log-file. See the description
         of --log-file for details.

         If the filename contains the extension .ms, then the
         produced file format will be a massif output file
         format. If the filename contains the extension .kcg or
         no extension is provided or recognised, then the
         produced file format will be a callgrind output format.

         See ???  for a detailed explanation about execution
         trees formats.

Uncommon Options
     These options apply to all tools, as they affect certain
     obscure workings of the Valgrind core. Most people won't
     need to use them.

     --smc-check=<none|stack|all|all-non-file> [default:
     all-non-file for x86/amd64/s390x, stack for other archs]
         This option controls Valgrind's detection of
         self-modifying code. If no checking is done, when a
         program executes some code, then overwrites it with new
         code, and executes the new code, Valgrind will continue
         to execute the translations it made for the old code.
         This will likely lead to incorrect behaviour and/or
         crashes.

         For "modern" architectures -- anything that's not x86,
         amd64 or s390x -- the default is stack. This is because
         a correct program must take explicit action to
         reestablish D-I cache coherence following code
         modification. Valgrind observes and honours such
         actions, with the result that self-modifying code is
         transparently handled with zero extra cost.

         For x86, amd64 and s390x, the program is not required to
         notify the hardware of required D-I coherence syncing.
         Hence the default is all-non-file, which covers the
         normal case of generating code into an anonymous
         (non-file-backed) mmap'd area.

         The meanings of the four available settings are as
         follows. No detection (none), detect self-modifying code
         on the stack (which is used by GCC to implement nested
         functions) (stack), detect self-modifying code
         everywhere (all), and detect self-modifying code
         everywhere except in file-backed mappings
         (all-non-file).

         Running with all will slow Valgrind down noticeably.
         Running with none will rarely speed things up, since
         very little code gets dynamically generated in most
         programs. The VALGRIND_DISCARD_TRANSLATIONS client
         request is an alternative to --smc-check=all and
         --smc-check=all-non-file that requires more programmer
         effort but allows Valgrind to run your program faster,
         by telling it precisely when translations need to be
         re-made.

         --smc-check=all-non-file provides a cheaper but more
         limited version of --smc-check=all. It adds checks to
         any translations that do not originate from file-backed
         memory mappings. Typical applications that generate
         code, for example JITs in web browsers, generate code
         into anonymous mmaped areas, whereas the "fixed" code of
         the browser always lives in file-backed mappings.
         --smc-check=all-non-file takes advantage of this
         observation, limiting the overhead of checking to code
         which is likely to be JIT generated.

     --read-inline-info=<yes|no> [default: see below]
         When enabled, Valgrind will read information about
         inlined function calls from DWARF3 debug info. This
         slows Valgrind startup and makes it use more memory
         (typically for each inlined piece of code, 6 words and
         space for the function name), but it results in more
         descriptive stacktraces. For the 3.10.0 release, this
         functionality is enabled by default only for Linux,
         Android and Solaris targets and only for the tools
         Memcheck, Helgrind and DRD. Here is an example of some
         stacktraces with --read-inline-info=no:

             ==15380== Conditional jump or move depends on uninitialised value(s)
             ==15380==    at 0x80484EA: main (inlinfo.c:6)
             ==15380==
             ==15380== Conditional jump or move depends on uninitialised value(s)
             ==15380==    at 0x8048550: fun_noninline (inlinfo.c:6)
             ==15380==    by 0x804850E: main (inlinfo.c:34)
             ==15380==
             ==15380== Conditional jump or move depends on uninitialised value(s)
             ==15380==    at 0x8048520: main (inlinfo.c:6)

         And here are the same errors with
         --read-inline-info=yes:

             ==15377== Conditional jump or move depends on uninitialised value(s)
             ==15377==    at 0x80484EA: fun_d (inlinfo.c:6)
             ==15377==    by 0x80484EA: fun_c (inlinfo.c:14)

             ==15377==    by 0x80484EA: fun_b (inlinfo.c:20)
             ==15377==    by 0x80484EA: fun_a (inlinfo.c:26)
             ==15377==    by 0x80484EA: main (inlinfo.c:33)
             ==15377==
             ==15377== Conditional jump or move depends on uninitialised value(s)
             ==15377==    at 0x8048550: fun_d (inlinfo.c:6)
             ==15377==    by 0x8048550: fun_noninline (inlinfo.c:41)
             ==15377==    by 0x804850E: main (inlinfo.c:34)
             ==15377==
             ==15377== Conditional jump or move depends on uninitialised value(s)
             ==15377==    at 0x8048520: fun_d (inlinfo.c:6)
             ==15377==    by 0x8048520: main (inlinfo.c:35)

     --read-var-info=<yes|no> [default: no]
         When enabled, Valgrind will read information about
         variable types and locations from DWARF3 debug info.
         This slows Valgrind startup significantly and makes it
         use significantly more memory, but for the tools that
         can take advantage of it (Memcheck, Helgrind, DRD) it
         can result in more precise error messages. For example,
         here are some standard errors issued by Memcheck:

             ==15363== Uninitialised byte(s) found during client check request
             ==15363==    at 0x80484A9: croak (varinfo1.c:28)
             ==15363==    by 0x8048544: main (varinfo1.c:55)
             ==15363==  Address 0x80497f7 is 7 bytes inside data symbol "global_i2"
             ==15363==
             ==15363== Uninitialised byte(s) found during client check request
             ==15363==    at 0x80484A9: croak (varinfo1.c:28)
             ==15363==    by 0x8048550: main (varinfo1.c:56)
             ==15363==  Address 0xbea0d0cc is on thread 1's stack
             ==15363==  in frame #1, created by main (varinfo1.c:45)

         And here are the same errors with --read-var-info=yes:

             ==15370== Uninitialised byte(s) found during client check request
             ==15370==    at 0x80484A9: croak (varinfo1.c:28)
             ==15370==    by 0x8048544: main (varinfo1.c:55)
             ==15370==  Location 0x80497f7 is 0 bytes inside global_i2[7],
             ==15370==  a global variable declared at varinfo1.c:41
             ==15370==
             ==15370== Uninitialised byte(s) found during client check request
             ==15370==    at 0x80484A9: croak (varinfo1.c:28)
             ==15370==    by 0x8048550: main (varinfo1.c:56)
             ==15370==  Location 0xbeb4a0cc is 0 bytes inside local var "local"
             ==15370==  declared at varinfo1.c:46, in frame #1 of thread 1

     --vgdb-poll=<number> [default: 5000]
         As part of its main loop, the Valgrind scheduler will
         poll to check if some activity (such as an external
         command or some input from a gdb) has to be handled by
         gdbserver. This activity poll will be done after having
         run the given number of basic blocks (or slightly more
         than the given number of basic blocks). This poll is
         quite cheap so the default value is set relatively low.
         You might further decrease this value if vgdb cannot use
         ptrace system call to interrupt Valgrind if all threads
         are (most of the time) blocked in a system call.

     --vgdb-shadow-registers=no|yes [default: no]
         When activated, gdbserver will expose the Valgrind
         shadow registers to GDB. With this, the value of the
         Valgrind shadow registers can be examined or changed
         using GDB. Exposing shadow registers only works with GDB
         version 7.1 or later.

     --vgdb-prefix=<prefix> [default: /tmp/vgdb-pipe]
         To communicate with gdb/vgdb, the Valgrind gdbserver
         creates 3 files (2 named FIFOs and a mmap shared memory
         file). The prefix option controls the directory and
         prefix for the creation of these files.

     --run-libc-freeres=<yes|no> [default: yes]
         This option is only relevant when running Valgrind on
         Linux.

         The GNU C library (libc.so), which is used by all
         programs, may allocate memory for its own uses. Usually
         it doesn't bother to free that memory when the program
         ends-there would be no point, since the Linux kernel
         reclaims all process resources when a process exits
         anyway, so it would just slow things down.

         The glibc authors realised that this behaviour causes
         leak checkers, such as Valgrind, to falsely report leaks
         in glibc, when a leak check is done at exit. In order to
         avoid this, they provided a routine called
         __libc_freeres specifically to make glibc release all
         memory it has allocated. Memcheck therefore tries to run
         __libc_freeres at exit.

         Unfortunately, in some very old versions of glibc,
         __libc_freeres is sufficiently buggy to cause
         segmentation faults. This was particularly noticeable on
         Red Hat 7.1. So this option is provided in order to
         inhibit the run of __libc_freeres. If your program seems
         to run fine on Valgrind, but segfaults at exit, you may
         find that --run-libc-freeres=no fixes that, although at
         the cost of possibly falsely reporting space leaks in
         libc.so.

     --run-cxx-freeres=<yes|no> [default: yes]
         This option is only relevant when running Valgrind on
         Linux or Solaris C++ programs.

         The GNU Standard C++ library (libstdc++.so), which is
         used by all C++ programs compiled with g++, may allocate
         memory for its own uses. Usually it doesn't bother to
         free that memory when the program ends-there would be no
         point, since the kernel reclaims all process resources
         when a process exits anyway, so it would just slow
         things down.

         The gcc authors realised that this behaviour causes leak
         checkers, such as Valgrind, to falsely report leaks in
         libstdc++, when a leak check is done at exit. In order
         to avoid this, they provided a routine called
         __gnu_cxx::__freeres specifically to make libstdc++
         release all memory it has allocated. Memcheck therefore
         tries to run __gnu_cxx::__freeres at exit.

         For the sake of flexibility and unforeseen problems with
         __gnu_cxx::__freeres, option --run-cxx-freeres=no
         exists, although at the cost of possibly falsely
         reporting space leaks in libstdc++.so.

     --sim-hints=hint1,hint2,...
         Pass miscellaneous hints to Valgrind which slightly
         modify the simulated behaviour in nonstandard or
         dangerous ways, possibly to help the simulation of
         strange features. By default no hints are enabled. Use
         with caution! Currently known hints are:

         *   lax-ioctls: Be very lax about ioctl handling; the
             only assumption is that the size is correct. Doesn't
             require the full buffer to be initialised when
             writing. Without this, using some device drivers
             with a large number of strange ioctl commands
             becomes very tiresome.

         *   fuse-compatible: Enable special handling for certain
             system calls that may block in a FUSE file-system.
             This may be necessary when running Valgrind on a
             multi-threaded program that uses one thread to
             manage a FUSE file-system and another thread to
             access that file-system.

         *   enable-outer: Enable some special magic needed when
             the program being run is itself Valgrind.

         *   no-inner-prefix: Disable printing a prefix > in
             front of each stdout or stderr output line in an
             inner Valgrind being run by an outer Valgrind. This
             is useful when running Valgrind regression tests in
             an outer/inner setup. Note that the prefix > will
             always be printed in front of the inner debug
             logging lines.

         *   no-nptl-pthread-stackcache: This hint is only
             relevant when running Valgrind on Linux.

             The GNU glibc pthread library (libpthread.so), which
             is used by pthread programs, maintains a cache of
             pthread stacks. When a pthread terminates, the
             memory used for the pthread stack and some thread
             local storage related data structure are not always
             directly released. This memory is kept in a cache
             (up to a certain size), and is re-used if a new
             thread is started.

             This cache causes the helgrind tool to report some
             false positive race condition errors on this cached
             memory, as helgrind does not understand the internal
             glibc cache synchronisation primitives. So, when
             using helgrind, disabling the cache helps to avoid
             false positive race conditions, in particular when
             using thread local storage variables (e.g. variables
             using the __thread qualifier).

             When using the memcheck tool, disabling the cache
             ensures the memory used by glibc to handle __thread
             variables is directly released when a thread
             terminates.

             Note: Valgrind disables the cache using some
             internal knowledge of the glibc stack cache
             implementation and by examining the debug
             information of the pthread library. This technique
             is thus somewhat fragile and might not work for all
             glibc versions. This has been successfully tested
             with various glibc versions (e.g. 2.11, 2.16, 2.18)
             on various platforms.

         *   lax-doors: (Solaris only) Be very lax about door
             syscall handling over unrecognised door file
             descriptors. Does not require that full buffer is
             initialised when writing. Without this, programs
             using libdoor(3LIB) functionality with completely
             proprietary semantics may report large number of
             false positives.

         *   fallback-llsc: (MIPS and ARM64 only): Enables an
             alternative implementation of Load-Linked (LL) and
             Store-Conditional (SC) instructions. The standard
             implementation gives more correct behaviour, but can
             cause indefinite looping on certain processor
             implementations that are intolerant of extra memory
             references between LL and SC. So far this is known
             only to happen on Cavium 3 cores. You should not
             need to use this flag, since the relevant cores are
             detected at startup and the alternative
             implementation is automatically enabled if
             necessary. There is no equivalent anti-flag: you
             cannot force-disable the alternative implementation,
             if it is automatically enabled. The underlying
             problem exists because the "standard" implementation
             of LL and SC is done by copying through LL and SC
             instructions into the instrumented code. However,
             tools may insert extra instrumentation memory
             references in between the LL and SC instructions.
             These memory references are not present in the
             original uninstrumented code, and their presence in
             the instrumented code can cause the SC instructions
             to persistently fail, leading to indefinite looping
             in LL-SC blocks. The alternative implementation
             gives correct behaviour of LL and SC instructions
             between threads in a process, up to and including
             the ABA scenario. It also gives correct behaviour
             between a Valgrinded thread and a non-Valgrinded
             thread running in a different process, that
             communicate via shared memory, but only up to and
             including correct CAS behaviour -- in this case the
             ABA scenario may not be correctly handled.

     --fair-sched=<no|yes|try> [default: no]
         The --fair-sched option controls the locking mechanism
         used by Valgrind to serialise thread execution. The
         locking mechanism controls the way the threads are
         scheduled, and different settings give different
         trade-offs between fairness and performance. For more
         details about the Valgrind thread serialisation scheme
         and its impact on performance and thread scheduling, see
         Scheduling and Multi-Thread Performance.

         *   The value --fair-sched=yes activates a fair
             scheduler. In short, if multiple threads are ready
             to run, the threads will be scheduled in a round
             robin fashion. This mechanism is not available on
             all platforms or Linux versions. If not available,
             using --fair-sched=yes will cause Valgrind to
             terminate with an error.

             You may find this setting improves overall
             responsiveness if you are running an interactive
             multithreaded program, for example a web browser, on
             Valgrind.

         *   The value --fair-sched=try activates fair scheduling
             if available on the platform. Otherwise, it will
             automatically fall back to --fair-sched=no.

         *   The value --fair-sched=no activates a scheduler

             which does not guarantee fairness between threads
             ready to run, but which in general gives the highest
             performance.

     --kernel-variant=variant1,variant2,...
         Handle system calls and ioctls arising from minor
         variants of the default kernel for this platform. This
         is useful for running on hacked kernels or with kernel
         modules which support nonstandard ioctls, for example.
         Use with caution. If you don't understand what this
         option does then you almost certainly don't need it.
         Currently known variants are:

         *   bproc: support the sys_broc system call on x86. This
             is for running on BProc, which is a minor variant of
             standard Linux which is sometimes used for building
             clusters.

         *   android-no-hw-tls: some versions of the Android
             emulator for ARM do not provide a hardware TLS
             (thread-local state) register, and Valgrind crashes
             at startup. Use this variant to select software
             support for TLS.

         *   android-gpu-sgx5xx: use this to support handling of
             proprietary ioctls for the PowerVR SGX 5XX series of
             GPUs on Android devices. Failure to select this does
             not cause stability problems, but may cause Memcheck
             to report false errors after the program performs
             GPU-specific ioctls.

         *   android-gpu-adreno3xx: similarly, use this to
             support handling of proprietary ioctls for the
             Qualcomm Adreno 3XX series of GPUs on Android
             devices.

     --merge-recursive-frames=<number> [default: 0]
         Some recursive algorithms, for example balanced binary
         tree implementations, create many different stack
         traces, each containing cycles of calls. A cycle is
         defined as two identical program counter values
         separated by zero or more other program counter values.
         Valgrind may then use a lot of memory to store all these
         stack traces. This is a poor use of memory considering
         that such stack traces contain repeated uninteresting
         recursive calls instead of more interesting information
         such as the function that has initiated the recursive
         call.

         The option --merge-recursive-frames=<number> instructs
         Valgrind to detect and merge recursive call cycles
         having a size of up to <number> frames. When such a
         cycle is detected, Valgrind records the cycle in the
         stack trace as a unique program counter.

         The value 0 (the default) causes no recursive call
         merging. A value of 1 will cause stack traces of simple
         recursive algorithms (for example, a factorial
         implementation) to be collapsed. A value of 2 will
         usually be needed to collapse stack traces produced by
         recursive algorithms such as binary trees, quick sort,
         etc. Higher values might be needed for more complex
         recursive algorithms.

         Note: recursive calls are detected by analysis of
         program counter values. They are not detected by looking
         at function names.

     --num-transtab-sectors=<number> [default: 6 for Android
     platforms, 16 for all others]
         Valgrind translates and instruments your program's
         machine code in small fragments (basic blocks). The
         translations are stored in a translation cache that is
         divided into a number of sections (sectors). If the
         cache is full, the sector containing the oldest
         translations is emptied and reused. If these old
         translations are needed again, Valgrind must
         re-translate and re-instrument the corresponding machine
         code, which is expensive. If the "executed instructions"
         working set of a program is big, increasing the number
         of sectors may improve performance by reducing the
         number of re-translations needed. Sectors are allocated
         on demand. Once allocated, a sector can never be freed,
         and occupies considerable space, depending on the tool
         and the value of --avg-transtab-entry-size (about 40 MB
         per sector for Memcheck). Use the option --stats=yes to
         obtain precise information about the memory used by a
         sector and the allocation and recycling of sectors.

     --avg-transtab-entry-size=<number> [default: 0, meaning use
     tool provided default]
         Average size of translated basic block. This average
         size is used to dimension the size of a sector. Each
         tool provides a default value to be used. If this
         default value is too small, the translation sectors will
         become full too quickly. If this default value is too
         big, a significant part of the translation sector memory
         will be unused. Note that the average size of a basic
         block translation depends on the tool, and might depend
         on tool options. For example, the memcheck option
         --track-origins=yes increases the size of the basic
         block translations. Use --avg-transtab-entry-size to
         tune the size of the sectors, either to gain memory or
         to avoid too many retranslations.

     --aspace-minaddr=<address> [default: depends on the
     platform]
         To avoid potential conflicts with some system libraries,
         Valgrind does not use the address space below
         --aspace-minaddr value, keeping it reserved in case a
         library specifically requests memory in this region. So,
         some "pessimistic" value is guessed by Valgrind
         depending on the platform. On linux, by default,
         Valgrind avoids using the first 64MB even if typically
         there is no conflict in this complete zone. You can use
         the option --aspace-minaddr to have your memory hungry
         application benefitting from more of this lower memory.
         On the other hand, if you encounter a conflict,
         increasing aspace-minaddr value might solve it.
         Conflicts will typically manifest themselves with mmap
         failures in the low range of the address space. The
         provided address must be page aligned and must be equal
         or bigger to 0x1000 (4KB). To find the default value on
         your platform, do something such as valgrind -d -d date
         2>&1 | grep -i minaddr. Values lower than 0x10000 (64KB)
         are known to create problems on some distributions.

     --valgrind-stacksize=<number> [default: 1MB]
         For each thread, Valgrind needs its own `private' stack.
         The default size for these stacks is largely
         dimensioned, and so should be sufficient in most cases.
         In case the size is too small, Valgrind will segfault.
         Before segfaulting, a warning might be produced by
         Valgrind when approaching the limit.

         Use the option --valgrind-stacksize if such an
         (unlikely) warning is produced, or Valgrind dies due to
         a segmentation violation. Such segmentation violations
         have been seen when demangling huge C++ symbols.

         If your application uses many threads and needs a lot of
         memory, you can gain some memory by reducing the size of
         these Valgrind stacks using the option
         --valgrind-stacksize.

     --show-emwarns=<yes|no> [default: no]
         When enabled, Valgrind will emit warnings about its CPU
         emulation in certain cases. These are usually not
         interesting.

     --require-text-symbol=:sonamepatt:fnnamepatt
         When a shared object whose soname matches sonamepatt is
         loaded into the process, examine all the text symbols it
         exports. If none of those match fnnamepatt, print an
         error message and abandon the run. This makes it
         possible to ensure that the run does not continue unless
         a given shared object contains a particular function
         name.

         Both sonamepatt and fnnamepatt can be written using the
         usual ?  and * wildcards. For example:
         ":*libc.so*:foo?bar". You may use characters other than
         a colon to separate the two patterns. It is only
         important that the first character and the separator
         character are the same. For example, the above example
         could also be written "Q*libc.so*Qfoo?bar". Multiple
          --require-text-symbol flags are allowed, in which case
         shared objects that are loaded into the process will be
         checked against all of them.

         The purpose of this is to support reliable usage of
         marked-up libraries. For example, suppose we have a
         version of GCC's libgomp.so which has been marked up
         with annotations to support Helgrind. It is only too
         easy and confusing to load the wrong, un-annotated
         libgomp.so into the application. So the idea is: add a
         text symbol in the marked-up library, for example
         annotated_for_helgrind_3_6, and then give the flag
         --require-text-symbol=:*libgomp*so*:annotated_for_helgrind_3_6
         so that when libgomp.so is loaded, Valgrind scans its
         symbol table, and if the symbol isn't present the run is
         aborted, rather than continuing silently with the
         un-marked-up library. Note that you should put the
         entire flag in quotes to stop shells expanding up the *
         and ?  wildcards.

     --soname-synonyms=syn1=pattern1,syn2=pattern2,...
         When a shared library is loaded, Valgrind checks for
         functions in the library that must be replaced or
         wrapped. For example, Memcheck replaces some string and
         memory functions (strchr, strlen, strcpy, memchr,
         memcpy, memmove, etc.) with its own versions. Such
         replacements are normally done only in shared libraries
         whose soname matches a predefined soname pattern (e.g.
         libc.so* on linux). By default, no replacement is done
         for a statically linked binary or for alternative
         libraries, except for the allocation functions (malloc,
         free, calloc, memalign, realloc, operator new, operator
         delete, etc.) Such allocation functions are intercepted
         by default in any shared library or in the executable if
         they are exported as global symbols. This means that if
         a replacement allocation library such as tcmalloc is
         found, its functions are also intercepted by default. In
         some cases, the replacements allow --soname-synonyms to
         specify one additional synonym pattern, giving
         flexibility in the replacement. Or to prevent
         interception of all public allocation symbols.

         Currently, this flexibility is only allowed for the
         malloc related functions, using the synonym somalloc.
         This synonym is usable for all tools doing standard
         replacement of malloc related functions (e.g. memcheck,
         massif, drd, helgrind, exp-dhat, exp-sgcheck).

         *   Alternate malloc library: to replace the malloc
             related functions in a specific alternate library
             with soname mymalloclib.so (and not in any others),
             give the option
             --soname-synonyms=somalloc=mymalloclib.so. A pattern
             can be used to match multiple libraries sonames. For
             example, --soname-synonyms=somalloc=*tcmalloc* will
             match the soname of all variants of the tcmalloc
             library (native, debug, profiled, ... tcmalloc
             variants).

             Note: the soname of a elf shared library can be
             retrieved using the readelf utility.

         *   Replacements in a statically linked library are done
             by using the NONE pattern. For example, if you link
             with libtcmalloc.a, and only want to intercept the
             malloc related functions in the executable (and
             standard libraries) themselves, but not any other
             shared libraries, you can give the option
             --soname-synonyms=somalloc=NONE. Note that a NONE
             pattern will match the main executable and any
             shared library having no soname.

         *   To run a "default" Firefox build for Linux, in which
             JEMalloc is linked in to the main executable, use
             --soname-synonyms=somalloc=NONE.

         *   To only intercept allocation symbols in the default
             system libraries, but not in any other shared
             library or the executable defining public malloc or
             operator new related functions use a non-existing
             library name like
             --soname-synonyms=somalloc=nouserintercepts (where
             nouserintercepts can be any non-existing library
             name).

         *   Shared library of the dynamic (runtime) linker is
             excluded from searching for global public symbols,
             such as those for the malloc related functions
             (identified by somalloc synonym).

Debugging Valgrind Options
     There are also some options for debugging Valgrind itself.
     You shouldn't need to use them in the normal run of things.
     If you wish to see the list, use the --help-debug option.

Memcheck Options
     --leak-check=<no|summary|yes|full> [default: summary]
         When enabled, search for memory leaks when the client
         program finishes. If set to summary, it says how many
         leaks occurred. If set to full or yes, each individual
         leak will be shown in detail and/or counted as an error,
         as specified by the options --show-leak-kinds and
         --errors-for-leak-kinds.

     --leak-resolution=<low|med|high> [default: high]
         When doing leak checking, determines how willing
         Memcheck is to consider different backtraces to be the
         same for the purposes of merging multiple leaks into a
         single leak report. When set to low, only the first two
         entries need match. When med, four entries have to
         match. When high, all entries need to match.

         For hardcore leak debugging, you probably want to use
         --leak-resolution=high together with --num-callers=40 or
         some such large number.

         Note that the --leak-resolution setting does not affect
         Memcheck's ability to find leaks. It only changes how
         the results are presented.

     --show-leak-kinds=<set> [default: definite,possible]
         Specifies the leak kinds to show in a full leak search,
         in one of the following ways:

         *   a comma separated list of one or more of definite
             indirect possible reachable.

         *   all to specify the complete set (all leak kinds). It
             is equivalent to
             --show-leak-kinds=definite,indirect,possible,reachable.

         *   none for the empty set.

     --errors-for-leak-kinds=<set> [default: definite,possible]
         Specifies the leak kinds to count as errors in a full
         leak search. The <set> is specified similarly to
         --show-leak-kinds

     --leak-check-heuristics=<set> [default: all]
         Specifies the set of leak check heuristics to be used
         during leak searches. The heuristics control which
         interior pointers to a block cause it to be considered
         as reachable. The heuristic set is specified in one of
         the following ways:

         *   a comma separated list of one or more of stdstring
             length64 newarray multipleinheritance.

         *   all to activate the complete set of heuristics. It
             is equivalent to
             --leak-check-heuristics=stdstring,length64,newarray,multipleinheritance.

         *   none for the empty set.

         Note that these heuristics are dependent on the layout
         of the objects produced by the C++ compiler. They have
         been tested with some gcc versions (e.g. 4.4 and 4.7).
         They might not work properly with other C++ compilers.

     --show-reachable=<yes|no> , --show-possibly-lost=<yes|no>
         These options provide an alternative way to specify the
         leak kinds to show:

         *   --show-reachable=no --show-possibly-lost=yes is
             equivalent to --show-leak-kinds=definite,possible.

         *   --show-reachable=no --show-possibly-lost=no is
             equivalent to --show-leak-kinds=definite.

         *   --show-reachable=yes is equivalent to
             --show-leak-kinds=all.

         Note that --show-possibly-lost=no has no effect if
         --show-reachable=yes is specified.

     --xtree-leak=<no|yes> [no]
         If set to yes, the results for the leak search done at
         exit will be output in a `Callgrind Format' execution
         tree file. Note that this automatically sets the option
         --leak-check=full. The produced file will contain the
         following events:

         *   RB : Reachable Bytes

         *   PB : Possibly lost Bytes

         *   IB : Indirectly lost Bytes

         *   DB : Definitely lost Bytes (direct plus indirect)

         *   DIB : Definitely Indirectly lost Bytes (subset of
             DB)

         *   RBk : reachable Blocks

         *   PBk : Possibly lost Blocks

         *   IBk : Indirectly lost Blocks

         *   DBk : Definitely lost Blocks

         The increase or decrease for all events above will also
         be output in the file to provide the delta (increase or
         decreaseà between 2 successive leak searches. For
         example, iRB is the increase of the RB event, dPBk is
         the decrease of PBk event. The values for the increase
         and decrease events will be zero for the first leak
         search done.

         See ???  for a detailed explanation about execution
         trees.

     --xtree-leak-file=<filename> [default: xtleak.kcg.%p]
         Specifies that Valgrind should produce the xtree leak
         report in the specified file. Any %p, %q or %n sequences
         appearing in the filename are expanded in exactly the
         same way as they are for --log-file. See the description
         of --log-file for details.

         See ???  for a detailed explanation about execution
         trees formats.

     --undef-value-errors=<yes|no> [default: yes]
         Controls whether Memcheck reports uses of undefined
         value errors. Set this to no if you don't want to see
         undefined value errors. It also has the side effect of
         speeding up Memcheck somewhat.

     --track-origins=<yes|no> [default: no]
         Controls whether Memcheck tracks the origin of
         uninitialised values. By default, it does not, which
         means that although it can tell you that an
         uninitialised value is being used in a dangerous way, it
         cannot tell you where the uninitialised value came from.
         This often makes it difficult to track down the root
         problem.

         When set to yes, Memcheck keeps track of the origins of
         all uninitialised values. Then, when an uninitialised
         value error is reported, Memcheck will try to show the
         origin of the value. An origin can be one of the
         following four places: a heap block, a stack allocation,
         a client request, or miscellaneous other sources (eg, a
         call to brk).

         For uninitialised values originating from a heap block,
         Memcheck shows where the block was allocated. For
         uninitialised values originating from a stack
         allocation, Memcheck can tell you which function
         allocated the value, but no more than that -- typically
         it shows you the source location of the opening brace of
         the function. So you should carefully check that all of
         the function's local variables are initialised properly.

         Performance overhead: origin tracking is expensive. It
         halves Memcheck's speed and increases memory use by a
         minimum of 100MB, and possibly more. Nevertheless it can
         drastically reduce the effort required to identify the
         root cause of uninitialised value errors, and so is
         often a programmer productivity win, despite running
         more slowly.

         Accuracy: Memcheck tracks origins quite accurately. To
         avoid very large space and time overheads, some
         approximations are made. It is possible, although
         unlikely, that Memcheck will report an incorrect origin,
         or not be able to identify any origin.

         Note that the combination --track-origins=yes and
         --undef-value-errors=no is nonsensical. Memcheck checks
         for and rejects this combination at startup.

     --partial-loads-ok=<yes|no> [default: yes]
         Controls how Memcheck handles 32-, 64-, 128- and 256-bit
         naturally aligned loads from addresses for which some
         bytes are addressable and others are not. When yes, such
         loads do not produce an address error. Instead, loaded
         bytes originating from illegal addresses are marked as
         uninitialised, and those corresponding to legal
         addresses are handled in the normal way.

         When no, loads from partially invalid addresses are
         treated the same as loads from completely invalid
         addresses: an illegal-address error is issued, and the
         resulting bytes are marked as initialised.

         Note that code that behaves in this way is in violation
         of the ISO C/C++ standards, and should be considered
         broken. If at all possible, such code should be fixed.

     --expensive-definedness-checks=<yes|no> [default: no]
         Controls whether Memcheck should employ more precise but
         also more expensive (time consuming) algorithms when
         checking the definedness of a value. The default setting
         is not to do that and it is usually sufficient. However,
         for highly optimised code valgrind may sometimes
         incorrectly complain. Invoking valgrind with
         --expensive-definedness-checks=yes helps but comes at a
         performance cost. Runtime degradation of 25% have been
         observed but the extra cost depends a lot on the
         application at hand.

     --keep-stacktraces=alloc|free|alloc-and-free|alloc-then-free|none
     [default: alloc-and-free]
         Controls which stack trace(s) to keep for malloc'd
         and/or free'd blocks.

         With alloc-then-free, a stack trace is recorded at
         allocation time, and is associated with the block. When
         the block is freed, a second stack trace is recorded,
         and this replaces the allocation stack trace. As a
         result, any "use after free" errors relating to this
         block can only show a stack trace for where the block
         was freed.

         With alloc-and-free, both allocation and the
         deallocation stack traces for the block are stored.
         Hence a "use after free" error will show both, which may
         make the error easier to diagnose. Compared to
         alloc-then-free, this setting slightly increases
         Valgrind's memory use as the block contains two
         references instead of one.

         With alloc, only the allocation stack trace is recorded
         (and reported). With free, only the deallocation stack
         trace is recorded (and reported). These values somewhat
         decrease Valgrind's memory and cpu usage. They can be
         useful depending on the error types you are searching
         for and the level of detail you need to analyse them.
         For example, if you are only interested in memory leak
         errors, it is sufficient to record the allocation stack
         traces.

         With none, no stack traces are recorded for malloc and
         free operations. If your program allocates a lot of
         blocks and/or allocates/frees from many different stack
         traces, this can significantly decrease cpu and/or
         memory required. Of course, few details will be reported
         for errors related to heap blocks.

         Note that once a stack trace is recorded, Valgrind keeps
         the stack trace in memory even if it is not referenced
         by any block. Some programs (for example, recursive
         algorithms) can generate a huge number of stack traces.
         If Valgrind uses too much memory in such circumstances,
         you can reduce the memory required with the options
         --keep-stacktraces and/or by using a smaller value for
         the option --num-callers.

         If you want to use --xtree-memory=full memory profiling
         (see ???  ), then you cannot specify
         --keep-stacktraces=free or --keep-stacktraces=none.

     --freelist-vol=<number> [default: 20000000]
         When the client program releases memory using free (in
         C) or delete (C++), that memory is not immediately made
         available for re-allocation. Instead, it is marked
         inaccessible and placed in a queue of freed blocks. The
         purpose is to defer as long as possible the point at
         which freed-up memory comes back into circulation. This
         increases the chance that Memcheck will be able to
         detect invalid accesses to blocks for some significant
         period of time after they have been freed.

         This option specifies the maximum total size, in bytes,
         of the blocks in the queue. The default value is twenty
         million bytes. Increasing this increases the total
         amount of memory used by Memcheck but may detect invalid
         uses of freed blocks which would otherwise go
         undetected.

     --freelist-big-blocks=<number> [default: 1000000]
         When making blocks from the queue of freed blocks
         available for re-allocation, Memcheck will in priority
         re-circulate the blocks with a size greater or equal to
         --freelist-big-blocks. This ensures that freeing big
         blocks (in particular freeing blocks bigger than
         --freelist-vol) does not immediately lead to a
         re-circulation of all (or a lot of) the small blocks in
         the free list. In other words, this option increases the
         likelihood to discover dangling pointers for the "small"
         blocks, even when big blocks are freed.

         Setting a value of 0 means that all the blocks are
         re-circulated in a FIFO order.

     --workaround-gcc296-bugs=<yes|no> [default: no]
         When enabled, assume that reads and writes some small
         distance below the stack pointer are due to bugs in GCC
         2.96, and does not report them. The "small distance" is
         256 bytes by default. Note that GCC 2.96 is the default
         compiler on some ancient Linux distributions (RedHat
         7.X) and so you may need to use this option. Do not use
         it if you do not have to, as it can cause real errors to
         be overlooked. A better alternative is to use a more
         recent GCC in which this bug is fixed.

         You may also need to use this option when working with
         GCC 3.X or 4.X on 32-bit PowerPC Linux. This is because
         GCC generates code which occasionally accesses below the
         stack pointer, particularly for floating-point to/from
         integer conversions. This is in violation of the 32-bit
         PowerPC ELF specification, which makes no provision for
         locations below the stack pointer to be accessible.

         This option is deprecated as of version 3.12 and may be
         removed from future versions. You should instead use
         --ignore-range-below-sp to specify the exact range of
         offsets below the stack pointer that should be ignored.
         A suitable equivalent is --ignore-range-below-sp=1024-1.

     --ignore-range-below-sp=<number>-<number>
         This is a more general replacement for the deprecated
         --workaround-gcc296-bugs option. When specified, it
         causes Memcheck not to report errors for accesses at the
         specified offsets below the stack pointer. The two
         offsets must be positive decimal numbers and -- somewhat
         counterintuitively -- the first one must be larger, in
         order to imply a non-wraparound address range to ignore.
         For example, to ignore 4 byte accesses at 8192 bytes
         below the stack pointer, use
         --ignore-range-below-sp=8192-8189. Only one range may be
         specified.

     --show-mismatched-frees=<yes|no> [default: yes]
         When enabled, Memcheck checks that heap blocks are
         deallocated using a function that matches the allocating
         function. That is, it expects free to be used to
         deallocate blocks allocated by malloc, delete for blocks
         allocated by new, and delete[] for blocks allocated by
         new[]. If a mismatch is detected, an error is reported.
         This is in general important because in some
         environments, freeing with a non-matching function can
         cause crashes.

         There is however a scenario where such mismatches cannot
         be avoided. That is when the user provides
         implementations of new/new[] that call malloc and of
         delete/delete[] that call free, and these functions are
         asymmetrically inlined. For example, imagine that
         delete[] is inlined but new[] is not. The result is that
         Memcheck "sees" all delete[] calls as direct calls to
         free, even when the program source contains no
         mismatched calls.

         This causes a lot of confusing and irrelevant error
         reports.  --show-mismatched-frees=no disables these
         checks. It is not generally advisable to disable them,
         though, because you may miss real errors as a result.

     --ignore-ranges=0xPP-0xQQ[,0xRR-0xSS]
         Any ranges listed in this option (and multiple ranges
         can be specified, separated by commas) will be ignored
         by Memcheck's addressability checking.

     --malloc-fill=<hexnumber>
         Fills blocks allocated by malloc, new, etc, but not by
         calloc, with the specified byte. This can be useful when
         trying to shake out obscure memory corruption problems.
         The allocated area is still regarded by Memcheck as
         undefined -- this option only affects its contents. Note
         that --malloc-fill does not affect a block of memory
         when it is used as argument to client requests

         VALGRIND_MEMPOOL_ALLOC or VALGRIND_MALLOCLIKE_BLOCK.

     --free-fill=<hexnumber>
         Fills blocks freed by free, delete, etc, with the
         specified byte value. This can be useful when trying to
         shake out obscure memory corruption problems. The freed
         area is still regarded by Memcheck as not valid for
         access -- this option only affects its contents. Note
         that --free-fill does not affect a block of memory when
         it is used as argument to client requests
         VALGRIND_MEMPOOL_FREE or VALGRIND_FREELIKE_BLOCK.

Cachegrind Options
     --I1=<size>,<associativity>,<line size>
         Specify the size, associativity and line size of the
         level 1 instruction cache.

     --D1=<size>,<associativity>,<line size>
         Specify the size, associativity and line size of the
         level 1 data cache.

     --LL=<size>,<associativity>,<line size>
         Specify the size, associativity and line size of the
         last-level cache.

     --cache-sim=no|yes [yes]
         Enables or disables collection of cache access and miss
         counts.

     --branch-sim=no|yes [no]
         Enables or disables collection of branch instruction and
         misprediction counts. By default this is disabled as it
         slows Cachegrind down by approximately 25%. Note that
         you cannot specify --cache-sim=no and --branch-sim=no
         together, as that would leave Cachegrind with no
         information to collect.

     --cachegrind-out-file=<file>
         Write the profile data to file rather than to the
         default output file, cachegrind.out.<pid>. The %p and %q
         format specifiers can be used to embed the process ID
         and/or the contents of an environment variable in the
         name, as is the case for the core option --log-file.

Callgrind Options
     --callgrind-out-file=<file>
         Write the profile data to file rather than to the
         default output file, callgrind.out.<pid>. The %p and %q
         format specifiers can be used to embed the process ID
         and/or the contents of an environment variable in the
         name, as is the case for the core option --log-file.
         When multiple dumps are made, the file name is modified
         further; see below.

     --dump-line=<no|yes> [default: yes]
         This specifies that event counting should be performed
         at source line granularity. This allows source
         annotation for sources which are compiled with debug
         information (-g).

     --dump-instr=<no|yes> [default: no]
         This specifies that event counting should be performed
         at per-instruction granularity. This allows for assembly
         code annotation. Currently the results can only be
         displayed by KCachegrind.

     --compress-strings=<no|yes> [default: yes]
         This option influences the output format of the profile
         data. It specifies whether strings (file and function
         names) should be identified by numbers. This shrinks the
         file, but makes it more difficult for humans to read
         (which is not recommended in any case).

     --compress-pos=<no|yes> [default: yes]
         This option influences the output format of the profile
         data. It specifies whether numerical positions are
         always specified as absolute values or are allowed to be
         relative to previous numbers. This shrinks the file
         size.

     --combine-dumps=<no|yes> [default: no]
         When enabled, when multiple profile data parts are to be
         generated these parts are appended to the same output
         file. Not recommended.

     --dump-every-bb=<count> [default: 0, never]
         Dump profile data every count basic blocks. Whether a
         dump is needed is only checked when Valgrind's internal
         scheduler is run. Therefore, the minimum setting useful
         is about 100000. The count is a 64-bit value to make
         long dump periods possible.

     --dump-before=<function>
         Dump when entering function.

     --zero-before=<function>
         Zero all costs when entering function.

     --dump-after=<function>
         Dump when leaving function.

     --instr-atstart=<yes|no> [default: yes]
         Specify if you want Callgrind to start simulation and
         profiling from the beginning of the program. When set to
         no, Callgrind will not be able to collect any
         information, including calls, but it will have at most a
         slowdown of around 4, which is the minimum Valgrind
         overhead. Instrumentation can be interactively enabled
         via callgrind_control -i on.

         Note that the resulting call graph will most probably
         not contain main, but will contain all the functions
         executed after instrumentation was enabled.
         Instrumentation can also programatically
         enabled/disabled. See the Callgrind include file
         callgrind.h for the macro you have to use in your source
         code.

         For cache simulation, results will be less accurate when
         switching on instrumentation later in the program run,
         as the simulator starts with an empty cache at that
         moment. Switch on event collection later to cope with
         this error.

     --collect-atstart=<yes|no> [default: yes]
         Specify whether event collection is enabled at beginning
         of the profile run.

         To only look at parts of your program, you have two
         possibilities:

          1. Zero event counters before entering the program part
             you want to profile, and dump the event counters to
             a file after leaving that program part.

          2. Switch on/off collection state as needed to only see
             event counters happening while inside of the program
             part you want to profile.

         The second option can be used if the program part you
         want to profile is called many times. Option 1, i.e.
         creating a lot of dumps is not practical here.

         Collection state can be toggled at entry and exit of a
         given function with the option --toggle-collect. If you
         use this option, collection state should be disabled at
         the beginning. Note that the specification of
         --toggle-collect implicitly sets --collect-state=no.

         Collection state can be toggled also by inserting the
         client request CALLGRIND_TOGGLE_COLLECT ; at the needed
         code positions.

     --toggle-collect=<function>
         Toggle collection on entry/exit of function.

     --collect-jumps=<no|yes> [default: no]
         This specifies whether information for (conditional)
         jumps should be collected. As above, callgrind_annotate
         currently is not able to show you the data. You have to
         use KCachegrind to get jump arrows in the annotated
         code.

     --collect-systime=<no|yes> [default: no]
         This specifies whether information for system call times
         should be collected.

     --collect-bus=<no|yes> [default: no]
         This specifies whether the number of global bus events
         executed should be collected. The event type "Ge" is
         used for these events.

     --cache-sim=<yes|no> [default: no]
         Specify if you want to do full cache simulation. By
         default, only instruction read accesses will be counted
         ("Ir"). With cache simulation, further event counters
         are enabled: Cache misses on instruction reads
         ("I1mr"/"ILmr"), data read accesses ("Dr") and related
         cache misses ("D1mr"/"DLmr"), data write accesses ("Dw")
         and related cache misses ("D1mw"/"DLmw"). For more
         information, see Cachegrind: a cache and branch-
         prediction profiler.

     --branch-sim=<yes|no> [default: no]
         Specify if you want to do branch prediction simulation.
         Further event counters are enabled: Number of executed
         conditional branches and related predictor misses
         ("Bc"/"Bcm"), executed indirect jumps and related misses
         of the jump address predictor ("Bi"/"Bim").

Helgrind Options
     --free-is-write=no|yes [default: no]
         When enabled (not the default), Helgrind treats freeing
         of heap memory as if the memory was written immediately
         before the free. This exposes races where memory is
         referenced by one thread, and freed by another, but
         there is no observable synchronisation event to ensure
         that the reference happens before the free.

         This functionality is new in Valgrind 3.7.0, and is
         regarded as experimental. It is not enabled by default
         because its interaction with custom memory allocators is
         not well understood at present. User feedback is
         welcomed.

     --track-lockorders=no|yes [default: yes]
         When enabled (the default), Helgrind performs lock order
         consistency checking. For some buggy programs, the large
         number of lock order errors reported can become
         annoying, particularly if you're only interested in race
         errors. You may therefore find it helpful to disable
         lock order checking.

     --history-level=none|approx|full [default: full]
         --history-level=full (the default) causes Helgrind
         collects enough information about "old" accesses that it
         can produce two stack traces in a race report -- both
         the stack trace for the current access, and the trace
         for the older, conflicting access. To limit memory
         usage, "old" accesses stack traces are limited to a
         maximum of 8 entries, even if --num-callers value is
         bigger.

         Collecting such information is expensive in both speed
         and memory, particularly for programs that do many
         inter-thread synchronisation events (locks, unlocks,
         etc). Without such information, it is more difficult to
         track down the root causes of races. Nonetheless, you
         may not need it in situations where you just want to
         check for the presence or absence of races, for example,
         when doing regression testing of a previously race-free
         program.

         --history-level=none is the opposite extreme. It causes
         Helgrind not to collect any information about previous
         accesses. This can be dramatically faster than
         --history-level=full.

         --history-level=approx provides a compromise between
         these two extremes. It causes Helgrind to show a full
         trace for the later access, and approximate information
         regarding the earlier access. This approximate
         information consists of two stacks, and the earlier
         access is guaranteed to have occurred somewhere between
         program points denoted by the two stacks. This is not as
         useful as showing the exact stack for the previous
         access (as --history-level=full does), but it is better
         than nothing, and it is almost as fast as
         --history-level=none.

     --conflict-cache-size=N [default: 1000000]
         This flag only has any effect at --history-level=full.

         Information about "old" conflicting accesses is stored
         in a cache of limited size, with LRU-style management.
         This is necessary because it isn't practical to store a
         stack trace for every single memory access made by the
         program. Historical information on not recently accessed
         locations is periodically discarded, to free up space in
         the cache.

         This option controls the size of the cache, in terms of
         the number of different memory addresses for which
         conflicting access information is stored. If you find
         that Helgrind is showing race errors with only one stack
         instead of the expected two stacks, try increasing this
         value.

         The minimum value is 10,000 and the maximum is
         30,000,000 (thirty times the default value). Increasing
         the value by 1 increases Helgrind's memory requirement
         by very roughly 100 bytes, so the maximum value will
         easily eat up three extra gigabytes or so of memory.

     --check-stack-refs=no|yes [default: yes]
         By default Helgrind checks all data memory accesses made
         by your program. This flag enables you to skip checking
         for accesses to thread stacks (local variables). This
         can improve performance, but comes at the cost of
         missing races on stack-allocated data.

     --ignore-thread-creation=<yes|no> [default: no]
         Controls whether all activities during thread creation
         should be ignored. By default enabled only on Solaris.
         Solaris provides higher throughput, parallelism and
         scalability than other operating systems, at the cost of
         more fine-grained locking activity. This means for
         example that when a thread is created under glibc, just
         one big lock is used for all thread setup. Solaris libc
         uses several fine-grained locks and the creator thread
         resumes its activities as soon as possible, leaving for
         example stack and TLS setup sequence to the created
         thread. This situation confuses Helgrind as it assumes
         there is some false ordering in place between creator
         and created thread; and therefore many types of race
         conditions in the application would not be reported. To
         prevent such false ordering, this command line option is
         set to yes by default on Solaris. All activity (loads,
         stores, client requests) is therefore ignored during:

         *   pthread_create() call in the creator thread

         *   thread creation phase (stack and TLS setup) in the
             created thread

         Also new memory allocated during thread creation is
         untracked, that is race reporting is suppressed there.
         DRD does the same thing implicitly. This is necessary
         because Solaris libc caches many objects and reuses them
         for different threads and that confuses Helgrind.

Drd Options

     --check-stack-var=<yes|no> [default: no]
         Controls whether DRD detects data races on stack
         variables. Verifying stack variables is disabled by
         default because most programs do not share stack
         variables over threads.

     --exclusive-threshold=<n> [default: off]
         Print an error message if any mutex or writer lock has
         been held longer than the time specified in
         milliseconds. This option enables the detection of lock
         contention.

     --join-list-vol=<n> [default: 10]
         Data races that occur between a statement at the end of
         one thread and another thread can be missed if memory
         access information is discarded immediately after a
         thread has been joined. This option allows to specify
         for how many joined threads memory access information
         should be retained.

      --first-race-only=<yes|no> [default: no]
         Whether to report only the first data race that has been
         detected on a memory location or all data races that
         have been detected on a memory location.

      --free-is-write=<yes|no> [default: no]
         Whether to report races between accessing memory and
         freeing memory. Enabling this option may cause DRD to
         run slightly slower. Notes:

         *   Don't enable this option when using custom memory
             allocators that use the VG_USERREQ__MALLOCLIKE_BLOCK
             and VG_USERREQ__FREELIKE_BLOCK because that would
             result in false positives.

         *   Don't enable this option when using
             reference-counted objects because that will result
             in false positives, even when that code has been
             annotated properly with ANNOTATE_HAPPENS_BEFORE and
             ANNOTATE_HAPPENS_AFTER. See e.g. the output of the
             following command for an example:  valgrind
             --tool=drd --free-is-write=yes
             drd/tests/annotate_smart_pointer.

      --report-signal-unlocked=<yes|no> [default: yes]
         Whether to report calls to pthread_cond_signal and
         pthread_cond_broadcast where the mutex associated with
         the signal through pthread_cond_wait or
         pthread_cond_timed_waitis not locked at the time the
         signal is sent. Sending a signal without holding a lock
         on the associated mutex is a common programming error
         which can cause subtle race conditions and unpredictable
         behavior. There exist some uncommon synchronization
         patterns however where it is safe to send a signal
         without holding a lock on the associated mutex.

     --segment-merging=<yes|no> [default: yes]
         Controls segment merging. Segment merging is an
         algorithm to limit memory usage of the data race
         detection algorithm. Disabling segment merging may
         improve the accuracy of the so-called `other segments'
         displayed in race reports but can also trigger an out of
         memory error.

     --segment-merging-interval=<n> [default: 10]
         Perform segment merging only after the specified number
         of new segments have been created. This is an advanced
         configuration option that allows to choose whether to
         minimize DRD's memory usage by choosing a low value or
         to let DRD run faster by choosing a slightly higher
         value. The optimal value for this parameter depends on
         the program being analyzed. The default value works well
         for most programs.

     --shared-threshold=<n> [default: off]
         Print an error message if a reader lock has been held
         longer than the specified time (in milliseconds). This
         option enables the detection of lock contention.

     --show-confl-seg=<yes|no> [default: yes]
         Show conflicting segments in race reports. Since this
         information can help to find the cause of a data race,
         this option is enabled by default. Disabling this option
         makes the output of DRD more compact.

     --show-stack-usage=<yes|no> [default: no]
         Print stack usage at thread exit time. When a program
         creates a large number of threads it becomes important
         to limit the amount of virtual memory allocated for
         thread stacks. This option makes it possible to observe
         how much stack memory has been used by each thread of
         the client program. Note: the DRD tool itself allocates
         some temporary data on the client thread stack. The
         space necessary for this temporary data must be
         allocated by the client program when it allocates stack
         memory, but is not included in stack usage reported by
         DRD.

     --ignore-thread-creation=<yes|no> [default: no]
         Controls whether all activities during thread creation
         should be ignored. By default enabled only on Solaris.
         Solaris provides higher throughput, parallelism and
         scalability than other operating systems, at the cost of
         more fine-grained locking activity. This means for
         example that when a thread is created under glibc, just
         one big lock is used for all thread setup. Solaris libc
         uses several fine-grained locks and the creator thread
         resumes its activities as soon as possible, leaving for
         example stack and TLS setup sequence to the created
         thread. This situation confuses DRD as it assumes there
         is some false ordering in place between creator and
         created thread; and therefore many types of race
         conditions in the application would not be reported. To
         prevent such false ordering, this command line option is
         set to yes by default on Solaris. All activity (loads,
         stores, client requests) is therefore ignored during:

         *   pthread_create() call in the creator thread

         *   thread creation phase (stack and TLS setup) in the
             created thread

     --trace-addr=<address> [default: none]
         Trace all load and store activity for the specified
         address. This option may be specified more than once.

     --ptrace-addr=<address> [default: none]
         Trace all load and store activity for the specified
         address and keep doing that even after the memory at
         that address has been freed and reallocated.

     --trace-alloc=<yes|no> [default: no]
         Trace all memory allocations and deallocations. May
         produce a huge amount of output.

     --trace-barrier=<yes|no> [default: no]
         Trace all barrier activity.

     --trace-cond=<yes|no> [default: no]
         Trace all condition variable activity.

     --trace-fork-join=<yes|no> [default: no]
         Trace all thread creation and all thread termination
         events.

     --trace-hb=<yes|no> [default: no]
         Trace execution of the ANNOTATE_HAPPENS_BEFORE(),
         ANNOTATE_HAPPENS_AFTER() and ANNOTATE_HAPPENS_DONE()
         client requests.

     --trace-mutex=<yes|no> [default: no]
         Trace all mutex activity.

     --trace-rwlock=<yes|no> [default: no]
         Trace all reader-writer lock activity.

     --trace-semaphore=<yes|no> [default: no]
         Trace all semaphore activity.

Massif Options
     --heap=<yes|no> [default: yes]
         Specifies whether heap profiling should be done.

     --heap-admin=<size> [default: 8]
         If heap profiling is enabled, gives the number of
         administrative bytes per block to use. This should be an
         estimate of the average, since it may vary. For example,
         the allocator used by glibc on Linux requires somewhere
         between 4 to 15 bytes per block, depending on various
         factors. That allocator also requires admin space for
         freed blocks, but Massif cannot account for this.

     --stacks=<yes|no> [default: no]
         Specifies whether stack profiling should be done. This
         option slows Massif down greatly, and so is off by
         default. Note that Massif assumes that the main stack
         has size zero at start-up. This is not true, but doing
         otherwise accurately is difficult. Furthermore, starting
         at zero better indicates the size of the part of the
         main stack that a user program actually has control
         over.

     --pages-as-heap=<yes|no> [default: no]
         Tells Massif to profile memory at the page level rather
         than at the malloc'd block level. See above for details.

     --depth=<number> [default: 30]
         Maximum depth of the allocation trees recorded for
         detailed snapshots. Increasing it will make Massif run
         somewhat more slowly, use more memory, and produce
         bigger output files.

     --alloc-fn=<name>
         Functions specified with this option will be treated as
         though they were a heap allocation function such as
         malloc. This is useful for functions that are wrappers
         to malloc or new, which can fill up the allocation trees
         with uninteresting information. This option can be
         specified multiple times on the command line, to name
         multiple functions.

         Note that the named function will only be treated this
         way if it is the top entry in a stack trace, or just
         below another function treated this way. For example, if
         you have a function malloc1 that wraps malloc, and
         malloc2 that wraps malloc1, just specifying
         --alloc-fn=malloc2 will have no effect. You need to
         specify --alloc-fn=malloc1 as well. This is a little
         inconvenient, but the reason is that checking for
         allocation functions is slow, and it saves a lot of time
         if Massif can stop looking through the stack trace
         entries as soon as it finds one that doesn't match
         rather than having to continue through all the entries.

         Note that C++ names are demangled. Note also that
         overloaded C++ names must be written in full. Single
         quotes may be necessary to prevent the shell from
         breaking them up. For example:

             --alloc-fn='operator new(unsigned, std::nothrow_t const&)'


     --ignore-fn=<name>
         Any direct heap allocation (i.e. a call to malloc, new,
         etc, or a call to a function named by an --alloc-fn
         option) that occurs in a function specified by this
         option will be ignored. This is mostly useful for
         testing purposes. This option can be specified multiple
         times on the command line, to name multiple functions.

         Any realloc of an ignored block will also be ignored,
         even if the realloc call does not occur in an ignored
         function. This avoids the possibility of negative heap
         sizes if ignored blocks are shrunk with realloc.

         The rules for writing C++ function names are the same as
         for --alloc-fn above.

     --threshold=<m.n> [default: 1.0]
         The significance threshold for heap allocations, as a
         percentage of total memory size. Allocation tree entries
         that account for less than this will be aggregated. Note
         that this should be specified in tandem with ms_print's
         option of the same name.

     --peak-inaccuracy=<m.n> [default: 1.0]
         Massif does not necessarily record the actual global
         memory allocation peak; by default it records a peak
         only when the global memory allocation size exceeds the
         previous peak by at least 1.0%. This is because there
         can be many local allocation peaks along the way, and
         doing a detailed snapshot for every one would be
         expensive and wasteful, as all but one of them will be
         later discarded. This inaccuracy can be changed (even to
         0.0%) via this option, but Massif will run drastically
         slower as the number approaches zero.

     --time-unit=<i|ms|B> [default: i]
         The time unit used for the profiling. There are three
         possibilities: instructions executed (i), which is good
         for most cases; real (wallclock) time (ms, i.e.
         milliseconds), which is sometimes useful; and bytes
         allocated/deallocated on the heap and/or stack (B),
         which is useful for very short-run programs, and for
         testing purposes, because it is the most reproducible
         across different machines.

     --detailed-freq=<n> [default: 10]
         Frequency of detailed snapshots. With --detailed-freq=1,
         every snapshot is detailed.

     --max-snapshots=<n> [default: 100]
         The maximum number of snapshots recorded. If set to N,
         for all programs except very short-running ones, the
         final number of snapshots will be between N/2 and N.

     --massif-out-file=<file> [default: massif.out.%p]
         Write the profile data to file rather than to the
         default output file, massif.out.<pid>. The %p and %q
         format specifiers can be used to embed the process ID
         and/or the contents of an environment variable in the
         name, as is the case for the core option --log-file.

Sgcheck Options
     There are no SGCheck-specific command-line options at
     present.

Bbv Options
     --bb-out-file=<name> [default: bb.out.%p]
         This option selects the name of the basic block vector
         file. The %p and %q format specifiers can be used to
         embed the process ID and/or the contents of an
         environment variable in the name, as is the case for the
         core option --log-file.

     --pc-out-file=<name> [default: pc.out.%p]
         This option selects the name of the PC file. This file
         holds program counter addresses and function name info
         for the various basic blocks. This can be used in
         conjunction with the basic block vector file to
         fast-forward via function names instead of just
         instruction counts. The %p and %q format specifiers can
         be used to embed the process ID and/or the contents of
         an environment variable in the name, as is the case for
         the core option --log-file.

     --interval-size=<number> [default: 100000000]
         This option selects the size of the interval to use. The
         default is 100 million instructions, which is a commonly
         used value. Other sizes can be used; smaller intervals
         can help programs with finer-grained phases. However
         smaller interval size can lead to accuracy issues due to
         warm-up effects (When fast-forwarding the various
         architectural features will be un-initialized, and it
         will take some number of instructions before they "warm
         up" to the state a full simulation would be at without
         the fast-forwarding. Large interval sizes tend to
         mitigate this.)

     --instr-count-only [default: no]
         This option tells the tool to only display instruction
         count totals, and to not generate the actual basic block
         vector file. This is useful for debugging, and for
         gathering instruction count info without generating the
         large basic block vector files.

Lackey Options
     --basic-counts=<no|yes> [default: yes]
         When enabled, Lackey prints the following statistics and
         information about the execution of the client program:

          1. The number of calls to the function specified by the
             --fnname option (the default is main). If the
             program has had its symbols stripped, the count will
             always be zero.

          2. The number of conditional branches encountered and
             the number and proportion of those taken.

          3. The number of superblocks entered and completed by
             the program. Note that due to optimisations done by
             the JIT, this is not at all an accurate value.

          4. The number of guest (x86, amd64, ppc, etc.)
             instructions and IR statements executed. IR is
             Valgrind's RISC-like intermediate representation via
             which all instrumentation is done.

          5. Ratios between some of these counts.

          6. The exit code of the client program.

     --detailed-counts=<no|yes> [default: no]
         When enabled, Lackey prints a table containing counts of
         loads, stores and ALU operations, differentiated by
         their IR types. The IR types are identified by their IR
         name ("I1", "I8", ... "I128", "F32", "F64", and "V128").

     --trace-mem=<no|yes> [default: no]
         When enabled, Lackey prints the size and address of
         almost every memory access made by the program. See the
         comments at the top of the file lackey/lk_main.c for
         details about the output format, how it works, and
         inaccuracies in the address trace. Note that this option
         produces immense amounts of output.

     --trace-superblocks=<no|yes> [default: no]
         When enabled, Lackey prints out the address of every
         superblock (a single entry, multiple exit, linear chunk
         of code) executed by the program. This is primarily of
         interest to Valgrind developers. See the comments at the
         top of the file lackey/lk_main.c for details about the
         output format. Note that this option produces large
         amounts of output.

     --fnname=<name> [default: main]
         Changes the function for which calls are counted when
         --basic-counts=yes is specified.

See Also
     cg_annotate(1), callgrind_annotate(1), callgrind_control(1),
     ms_print(1), $INSTALL/share/doc/valgrind/html/index.html or
     http://www.valgrind.org/docs/manual/index.html,
     m[blue]Debugging your program using Valgrind's gdbserver and
     GDBm[][1] m[blue]vgdbm[][2], m[blue]Valgrind monitor
     commandsm[][3], m[blue]The Commentarym[][4],
     m[blue]Scheduling and Multi-Thread Performancem[][5],
     m[blue]Cachegrind: a cache and branch-prediction
     profilerm[][6].

Author
     See the AUTHORS file in the valgrind distribution for a
     comprehensive list of authors.

     This manpage was written by Andres Roldan
     <aroldan@debian.org> and the Valgrind developers.

Notes
      1. Debugging your program using Valgrind's gdbserver and
         GDB
         http://www.valgrind.org/docs/manual/manual-core-adv.html#manual-core-adv.gdbserver

      2. vgdb
         http://www.valgrind.org/docs/manual/manual-core-adv.html#manual-core-adv.vgdb

      3. Valgrind monitor commands
         http://www.valgrind.org/docs/manual/manual-core-adv.html#manual-core-adv.valgrind-monitor-commands

      4. The Commentary
         http://www.valgrind.org/docs/manual/manual-core.html#manual-core.comment

      5. Scheduling and Multi-Thread Performance
         http://www.valgrind.org/docs/manual/manual-core.html#manual-core.pthreads_perf_sched

      6. Cachegrind: a cache and branch-prediction profiler
         http://www.valgrind.org/docs/manual/cg-manual.html
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