VALGRIND(1) Release 3.13.0 VALGRIND(1)
valgrind - a suite of tools for debugging and profiling programs
SYNOPSIS top
valgrind [valgrind-options] [your-program] [your-program-options]
DESCRIPTION top
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 top
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 top
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 startupexitvalgrindabexit 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 top
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 top
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 top
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; it is ignored on Solaris and Mac
OS X.
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 top
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 top
--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 top
--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 top
--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 top
--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 top
--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 top
--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 top
There are no SGCheck-specific command-line options at present.
BBV OPTIONS top
--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 top
--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 top
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, Debugging your
program using Valgrind's gdbserver and GDB[1]vgdb[2], Valgrind
monitor commands[3], The Commentary[4], Scheduling and Multi-Thread
Performance[5], Cachegrind: a cache and branch-prediction
profiler[6].
AUTHOR top
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.
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
COLOPHON top
This page is part of the valgrind (a system for debugging and
profiling Linux programs) project. Information about the project can
be found at ⟨http://www.valgrind.org/⟩. If you have a bug report for
this manual page, see
⟨http://www.valgrind.org/support/bug_reports.html⟩. This page was
obtained from the project's upstream Subversion repository
⟨svn://svn.valgrind.org/valgrind/trunk⟩ on 2017-07-05. If you dis‐
cover any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page, or
you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a mail
to man-pages@man7.org