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VALGRIND(1)                      Release 3.8.0                     VALGRIND(1)



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, 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 ???  for a
           detailed description.

           If the embedded gdbserver is enabled but no gdb is currently being used, the ???  command line utility can
           send "monitor commands" to Valgrind from a shell. The Valgrind core provides a set of ???. 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.

       --track-fds=<yes|no> [default: no]
           When enabled, Valgrind will print out a list of open file descriptors on exit. 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.

           %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.

       --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.

       --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.

       --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.

       --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] ----

           The prompt's behaviour is the same as for the --db-attach option (see below).

           If you choose to, Valgrind will print out 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.

       --db-attach=<yes|no> [default: no]
           When enabled, Valgrind will pause after every error shown and print the line:

                   ---- Attach to debugger ? --- [Return/N/n/Y/y/C/c] ----

           Pressing Ret, or N Ret or n Ret, causes Valgrind not to start a debugger for this error.

           Pressing Y Ret or y Ret causes Valgrind to start a debugger for the program at this point. When you have
           finished with the debugger, quit from it, and the program will continue. Trying to continue from inside the
           debugger doesn't work.

           Note: if you use GDB, more powerful debugging support is provided by the --vgdb= yes or full value. This
           activates Valgrind's internal gdbserver, which provides more-or-less full GDB-style control of the
           application: insertion of breakpoints, continuing from inside GDB, inferior function calls, and much more.

           C Ret or c Ret causes Valgrind not to start a debugger, and not to ask again.

       --db-command=<command> [default: gdb -nw %f %p]
           Specify the debugger to use with the --db-attach command. The default debugger is GDB. This option is a
           template that is expanded by Valgrind at runtime.  %f is replaced with the executable's file name and %p is
           replaced by the process ID of the executable.

           This specifies how Valgrind will invoke the debugger. By default it will use whatever GDB is detected at
           build time, which is usually /usr/bin/gdb. Using this command, you can specify some alternative command to
           invoke the debugger you want to use.

           The command string given can include one or instances of the %p and %f expansions. Each instance of %p
           expands to the PID of the process to be debugged and each instance of %f expands to the path to the
           executable for the process to be debugged.

           Since <command> is likely to contain spaces, you will need to put this entire option in quotes to ensure it
           is correctly handled by the shell.

       --input-fd=<number> [default: 0, stdin]
           When using --db-attach=yes or --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 [no]
           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.

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.

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: stack]
           This option controls Valgrind's detection of self-modifying code. If no checking is done, if 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.

           Valgrind has four levels of self-modifying code detection: no detection, detect self-modifying code on the
           stack (which is used by GCC to implement nested functions), detect self-modifying code everywhere, and
           detect self-modifying code everywhere except in file-backed mappings. Note that the default option will
           catch the vast majority of cases. The main case it will not catch is programs such as JIT compilers that
           dynamically generate code and subsequently overwrite part or all of it. Running with all will slow Valgrind
           down noticeably. Running with none will rarely speed things up, since very little code gets put on the
           stack for most programs. The VALGRIND_DISCARD_TRANSLATIONS client request is an alternative to
           --smc-check=all 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.

           Some architectures (including ppc32, ppc64, ARM and MIPS) require programs which create code at runtime to
           flush the instruction cache in between code generation and first use. Valgrind observes and honours such
           instructions. Hence, on ppc32/Linux, ppc64/Linux and ARM/Linux, Valgrind always provides complete,
           transparent support for self-modifying code. It is only on platforms such as x86/Linux, AMD64/Linux,
           x86/Darwin and AMD64/Darwin that you need to use this option.

       --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 down and makes it use 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:

               ==15516== Uninitialised byte(s) found during client check request
               ==15516==    at 0x400633: croak (varinfo1.c:28)
               ==15516==    by 0x4006B2: main (varinfo1.c:55)
               ==15516==  Address 0x60103b is 7 bytes inside data symbol "global_i2"
               ==15516==
               ==15516== Uninitialised byte(s) found during client check request
               ==15516==    at 0x400633: croak (varinfo1.c:28)
               ==15516==    by 0x4006BC: main (varinfo1.c:56)
               ==15516==  Address 0x7fefffefc is on thread 1's stack

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

               ==15522== Uninitialised byte(s) found during client check request
               ==15522==    at 0x400633: croak (varinfo1.c:28)
               ==15522==    by 0x4006B2: main (varinfo1.c:55)
               ==15522==  Location 0x60103b is 0 bytes inside global_i2[7],
               ==15522==  a global variable declared at varinfo1.c:41
               ==15522==
               ==15522== Uninitialised byte(s) found during client check request
               ==15522==    at 0x400633: croak (varinfo1.c:28)
               ==15522==    by 0x4006BC: main (varinfo1.c:56)
               ==15522==  Location 0x7fefffefc is 0 bytes inside local var "local"
               ==15522==  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.

       --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 initialized when writing. Without this, using some device drivers with a
               large number of strange ioctl commands becomes very tiresome.

           ?   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.

           ?   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.

       --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 ???.

           ?   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.

       --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 all malloc related functions (malloc, free, calloc, ...) with its
           own versions. Such replacements are done by default 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 library or for alternative libraries such as tcmalloc. In some cases, the replacements allow
           --soname-synonyms to specify one additional synonym pattern, giving flexibility in the replacement.

           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 an alternate library with soname
               mymalloclib.so, 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, memcheck will properly work when you 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.

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, it also gives details of each individual leak.

       --show-possibly-lost=<yes|no> [default: yes]
           When disabled, the memory leak detector will not show "possibly lost" blocks.

       --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-reachable=<yes|no> [default: no]
           When disabled, the memory leak detector only shows "definitely lost" and "possibly lost" blocks. When
           enabled, the leak detector also shows "reachable" and "indirectly lost" blocks. (In other words, it shows
           all blocks, except suppressed ones, so --show-all would be a better name for it.)

       --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: no]
           Controls how Memcheck handles word-sized, word-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 the ISO C/C++ standards, and should be
           considered broken. If at all possible, such code should be fixed. This option should be used only as a last
           resort.

       --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.

       --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 ???.

       --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.

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 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.

       --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
       <xi:include></xi:include>.SH "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.

AUTHOR
       The Valgrind developers.

       This manpage was written by Andres Roldan <aroldanATdebian.org> and the Valgrind developers.



Release 3.8.0                     09/18/2012                       VALGRIND(1)