VALGRIND(1) Release 3.5.0 VALGRIND(1)NAMEvalgrind - a suite of tools for debugging and profiling programs
SYNOPSISvalgrind [valgrind-options] [your-program] [your-program-options]
DESCRIPTION
Valgrind is a flexible program for debugging and profiling Linux
executables. It consists of a core, which provides a synthetic CPU in
software, and a series of debugging and profiling tools. The
architecture is modular, so that new tools can be created easily and
without disturbing the existing structure.
Some of the options described below work with all Valgrind tools, and
some only work with a few or one. The section MEMCHECK OPTIONS and
those below it describe tool-specific options.
This manual page covers only basic usage and options. For more
comprehensive information, please see the HTML documentation on your
system: $INSTALL/share/doc/valgrind/html/index.html, or online:
http://www.valgrind.org/docs/manual/index.html.
BASIC OPTIONS
These options work with all tools.
-h --help
Show help for all options, both for the core and for the
selected tool.
--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.
--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.
--track-fds=<yes|no> [default: no]
When enabled, Valgrind will print out a list of open file
descriptors on exit. Along with each file descriptor is printed
a stack backtrace of where the file was opened and any details
relating to the file descriptor such as the file name or socket
details.
--time-stamp=<yes|no> [default: no]
When enabled, each message is preceded with an indication of the
elapsed wallclock time since startup, expressed as days, hours,
minutes, seconds and milliseconds.
--log-fd=<number> [default: 2, stderr]
Specifies that Valgrind should send all of its messages to the
specified file descriptor. The default, 2, is the standard error
channel (stderr). Note that this may interfere with the client's
own use of stderr, as Valgrind's output will be interleaved with
any output that the client sends to stderr.
--log-file=<filename>
Specifies that Valgrind should send all of its messages to the
specified file. If the file name is empty, it causes an abort.
There are three special format specifiers that can be used in
the file name.
%p is replaced with the current process ID. This is very useful
for program that invoke multiple processes. WARNING: If you use
--trace-children=yes and your program invokes multiple processes
OR your program forks without calling exec afterwards, and you
don't use this specifier (or the %q specifier below), the
Valgrind output from all those processes will go into one file,
possibly jumbled up, and possibly incomplete.
%q{FOO} is replaced with the contents of the environment
variable FOO. If the {FOO} part is malformed, it causes an
abort. This specifier is rarely needed, but very useful in
certain circumstances (eg. when running MPI programs). The idea
is that you specify a variable which will be set differently for
each process in the job, for example BPROC_RANK or whatever is
applicable in your MPI setup. If the named environment variable
is not set, it causes an abort. Note that in some shells, the {
and } characters may need to be escaped with a backslash.
%% is replaced with %.
If an % is followed by any other character, it causes an abort.
--log-socket=<ip-address:port-number>
Specifies that Valgrind should send all of its messages to the
specified port at the specified IP address. The port may be
omitted, in which case port 1500 is used. If a connection cannot
be made to the specified socket, Valgrind falls back to writing
output to the standard error (stderr). This option is intended
to be used in conjunction with the valgrind-listener program.
For further details, see the commentary in the manual.
ERROR-RELATED OPTIONS
These options are used by all tools that can report errors, e.g.
Memcheck, but not Cachegrind.
--xml=<yes|no> [default: no]
When enabled, the important parts of the output (e.g. tool error
messages) will be in XML format rather than plain text.
Furthermore, the XML output will be sent to a different output
channel than the plain text output. Therefore, you also must use
one of --xml-fd, --xml-file or --xml-socket to specify where the
XML is to be sent.
Less important messages will still be printed in plain text, but
because the XML output and plain text output are sent to
different output channels (the destination of the plain text
output is still controlled by --log-fd, --log-file and
--log-socket) this should not cause problems.
This option is aimed at making life easier for tools that
consume Valgrind's output as input, such as GUI front ends.
Currently this option works with Memcheck, Helgrind and
Ptrcheck. 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 50. Note that higher settings will
make Valgrind run a bit more slowly and take a bit more memory,
but can be useful when working with programs with deeply-nested
call chains.
--error-limit=<yes|no> [default: yes]
When enabled, Valgrind stops reporting errors after 10,000,000
in total, or 1,000 different ones, have been seen. This is to
stop the error tracking machinery from becoming a huge
performance overhead in programs with many errors.
--error-exitcode=<number> [default: 0]
Specifies an alternative exit code to return if Valgrind
reported any errors in the run. When set to the default value
(zero), the return value from Valgrind will always be the return
value of the process being simulated. When set to a nonzero
value, that value is returned instead, if Valgrind detects any
errors. This is useful for using Valgrind as part of an
automated test suite, since it makes it easy to detect test
cases for which Valgrind has reported errors, just by inspecting
return codes.
--show-below-main=<yes|no> [default: no]
By default, stack traces for errors do not show any functions
that appear beneath main because most of the time it's
uninteresting C library stuff and/or gobbledygook.
Alternatively, if main is not present in the stack trace, stack
traces will not show any functions below main-like functions
such as glibc's __libc_start_main. Furthermore, if main-like
functions are present in the trace, they are normalised as
(below main), in order to make the output more deterministic.
If this option is enabled, all stack trace entries will be shown
and main-like functions will not be normalised.
--suppressions=<filename> [default: $PREFIX/lib/valgrind/default.supp]
Specifies an extra file from which to read descriptions of
errors to suppress. You may use up to 100 extra suppression
files.
--gen-suppressions=<yes|no|all> [default: no]
When set to yes, Valgrind will pause after every error shown and
print the line:
---- Print suppression ? --- [Return/N/n/Y/y/C/c] ----
The prompt's behaviour is the same as for the --db-attach option
(see below).
If you choose to, Valgrind will print out a suppression for this
error. You can then cut and paste it into a suppression file if
you don't want to hear about the error in the future.
When set to all, Valgrind will print a suppression for every
reported error, without querying the user.
This option is particularly useful with C++ programs, as it
prints out the suppressions with mangled names, as required.
Note that the suppressions printed are as specific as possible.
You may want to common up similar ones, by adding wildcards to
function names, and by using frame-level wildcards. The
wildcarding facilities are powerful yet flexible, and with a bit
of careful editing, you may be able to suppress a whole family
of related errors with only a few suppressions.
Sometimes two different errors are suppressed by the same
suppression, in which case Valgrind will output the suppression
more than once, but you only need to have one copy in your
suppression file (but having more than one won't cause
problems). Also, the suppression name is given as <insert a
suppression name here>; the name doesn't really matter, it's
only used with the -v option which prints out all used
suppression records.
--db-attach=<yes|no> [default: no]
When enabled, Valgrind will pause after every error shown and
print the line:
---- Attach to debugger ? --- [Return/N/n/Y/y/C/c] ----
Pressing Ret, or N Ret or n Ret, causes Valgrind not to start a
debugger for this error.
Pressing Y Ret or y Ret causes Valgrind to start a debugger for
the program at this point. When you have finished with the
debugger, quit from it, and the program will continue. Trying to
continue from inside the debugger doesn't work.
C Ret or c Ret causes Valgrind not to start a debugger, and not
to ask again.
--db-command=<command> [default: gdb -nw %f %p]
Specify the debugger to use with the --db-attach command. The
default debugger is GDB. This option is a template that is
expanded by Valgrind at runtime. %f is replaced with the
executable's file name and %p is replaced by the process ID of
the executable.
This specifies how Valgrind will invoke the debugger. By default
it will use whatever GDB is detected at build time, which is
usually /usr/bin/gdb. Using this command, you can specify some
alternative command to invoke the debugger you want to use.
The command string given can include one or instances of the %p
and %f expansions. Each instance of %p expands to the PID of the
process to be debugged and each instance of %f expands to the
path to the executable for the process to be debugged.
Since <command> is likely to contain spaces, you will need to
put this entire option in quotes to ensure it is correctly
handled by the shell.
--input-fd=<number> [default: 0, stdin]
When using --db-attach=yes or --gen-suppressions=yes, Valgrind
will stop so as to read keyboard input from you when each error
occurs. By default it reads from the standard input (stdin),
which is problematic for programs which close stdin. This option
allows you to specify an alternative file descriptor from which
to read input.
--dsymutil=no|yes [no]
This option is only relevant when running Valgrind on Mac OS X.
Mac OS X uses a deferred debug information (debuginfo) linking
scheme. When object files containing debuginfo are linked into a
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
With --dsymutil=no, Valgrind will detect cases where the
directory is either missing, or is present but does not appear
to match the associated executable or
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 directories to be silently deleted and re-created.
Also note the 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. On AIX5 the allowed stack size is restricted to
128MB.
--main-stacksize only affects the stack size for the program's
initial thread. It has no bearing on the size of thread stacks,
as Valgrind does not allocate those.
You may need to use both --main-stacksize and --max-stackframe
together. It is important to understand that --main-stacksize
sets the maximum total stack size, whilst --max-stackframe
specifies the largest size of any one stack frame. You will have
to work out the --main-stacksize value for yourself (usually, if
your applications segfaults). But Valgrind will tell you the
needed --max-stackframe size, if necessary.
As discussed further in the description of --max-stackframe, a
requirement for a large stack is a sign of potential portability
problems. You are best advised to place all large data in
heap-allocated memory.
MALLOC()-RELATED OPTIONS
For tools that use their own version of malloc (e.g. Memcheck and
Massif), 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.
UNCOMMON OPTIONS
These options apply to all tools, as they affect certain obscure
workings of the Valgrind core. Most people won't need to use these.
--smc-check=<none|stack|all> [default: stack]
This option controls Valgrind's detection of self-modifying
code. If no checking is done, if a program executes some code,
then overwrites it with new code, and executes the new code,
Valgrind will continue to execute the translations it made for
the old code. This will likely lead to incorrect behaviour
and/or crashes.
Valgrind has three levels of self-modifying code detection: no
detection, detect self-modifying code on the stack (which used
by GCC to implement nested functions), or detect self-modifying
code everywhere. Note that the default option will catch the
vast majority of cases. The main case it will not catch is
programs such as JIT compilers that dynamically generate code
and subsequently overwrite part or all of it. Running with all
will slow Valgrind down greatly. Running with none will rarely
speed things up, since very little code gets put on the stack
for most programs. The VALGRIND_DISCARD_TRANSLATIONS client
request is an alternative to --smc-check=all that requires more
effort but is much faster.
Some architectures (including ppc32 and ppc64) require programs
which create code at runtime to flush the instruction cache in
between code generation and first use. Valgrind observes and
honours such instructions. Hence, on ppc32/Linux and
ppc64/Linux, Valgrind always provides complete, transparent
support for self-modifying code. It is only on platforms such as
x86/Linux, AMD64/Linux and x86/Darwin that you need to use this
option.
--read-var-info=<yes|no> [default: no]
When enabled, Valgrind will read information about variable
types and locations from DWARF3 debug info. This slows Valgrind
down and makes it use more memory, but for the tools that can
take advantage of it (Memcheck, Helgrind, DRD) it can result in
more precise error messages. For example, here are some standard
errors issued by Memcheck:
==15516== Uninitialised byte(s) found during client check request
==15516== at 0x400633: croak (varinfo1.c:28)
==15516== by 0x4006B2: main (varinfo1.c:55)
==15516== Address 0x60103b is 7 bytes inside data symbol "global_i2"
==15516==
==15516== Uninitialised byte(s) found during client check request
==15516== at 0x400633: croak (varinfo1.c:28)
==15516== by 0x4006BC: main (varinfo1.c:56)
==15516== Address 0x7fefffefc is on thread 1's stack
And here are the same errors with --read-var-info=yes:
==15522== Uninitialised byte(s) found during client check request
==15522== at 0x400633: croak (varinfo1.c:28)
==15522== by 0x4006B2: main (varinfo1.c:55)
==15522== Location 0x60103b is 0 bytes inside global_i2[7],
==15522== a global variable declared at varinfo1.c:41
==15522==
==15522== Uninitialised byte(s) found during client check request
==15522== at 0x400633: croak (varinfo1.c:28)
==15522== by 0x4006BC: main (varinfo1.c:56)
==15522== Location 0x7fefffefc is 0 bytes inside local var "local"
==15522== declared at varinfo1.c:46, in frame #1 of thread 1
--run-libc-freeres=<yes|no> [default: yes]
This option is only relevant when running Valgrind on Linux.
The GNU C library (libc.so), which is used by all programs, may
allocate memory for its own uses. Usually it doesn't bother to
free that memory when the program ends—there would be no point,
since the Linux kernel reclaims all process resources when a
process exits anyway, so it would just slow things down.
The glibc authors realised that this behaviour causes leak
checkers, such as Valgrind, to falsely report leaks in glibc,
when a leak check is done at exit. In order to avoid this, they
provided a routine called __libc_freeres specifically to make
glibc release all memory it has allocated. Memcheck therefore
tries to run __libc_freeres at exit.
Unfortunately, in some very old versions of glibc,
__libc_freeres is sufficiently buggy to cause segmentation
faults. This was particularly noticeable on Red Hat 7.1. So this
option is provided in order to inhibit the run of
__libc_freeres. If your program seems to run fine on Valgrind,
but segfaults at exit, you may find that --run-libc-freeres=no
fixes that, although at the cost of possibly falsely reporting
space leaks in libc.so.
--sim-hints=hint1,hint2,...
Pass miscellaneous hints to Valgrind which slightly modify the
simulated behaviour in nonstandard or dangerous ways, possibly
to help the simulation of strange features. By default no hints
are enabled. Use with caution! Currently known hints are:
· lax-ioctls: Be very lax about ioctl handling; the only
assumption is that the size is correct. Doesn't require the
full buffer to be initialized when writing. Without this,
using some device drivers with a large number of strange
ioctl commands becomes very tiresome.
· enable-inner: Enable some special magic needed when the
program being run is itself Valgrind.
--kernel-variant=variant1,variant2,...
Handle system calls and ioctls arising from minor variants of
the default kernel for this platform. This is useful for running
on hacked kernels or with kernel modules which support
nonstandard ioctls, for example. Use with caution. If you don't
understand what this option does then you almost certainly don't
need it. Currently known variants are:
· bproc: Support the sys_broc system call on x86. This is for
running on BProc, which is a minor variant of standard Linux
which is sometimes used for building clusters.
--show-emwarns=<yes|no> [default: no]
When enabled, Valgrind will emit warnings about its CPU
emulation in certain cases. These are usually not interesting.
DEBUGGING VALGRIND OPTIONS
There are also some options for debugging Valgrind itself. You
shouldn't need to use them in the normal run of things. If you wish to
see the list, use the --help-debug option.
MEMCHECK OPTIONS
--leak-check=<no|summary|yes|full> [default: summary]
When enabled, search for memory leaks when the client program
finishes. If set to summary, it says how many leaks occurred. If
set to full or yes, it also gives details of each individual
leak.
--leak-resolution=<low|med|high> [default: high]
When doing leak checking, determines how willing Memcheck is to
consider different backtraces to be the same for the purposes of
merging multiple leaks into a single leak report. When set to
low, only the first two entries need match. When med, four
entries have to match. When high, all entries need to match.
For hardcore leak debugging, you probably want to use
--leak-resolution=high together with --num-callers=40 or some
such large number.
Note that the --leak-resolution setting does not affect
Memcheck's ability to find leaks. It only changes how the
results are presented.
--show-reachable=<yes|no> [default: no]
When disabled, the memory leak detector only shows "definitely
lost" and "possibly lost" blocks. When enabled, the leak
detector also shows "reachable" and "indirectly lost" blocks.
(In other words, it shows all blocks, except suppressed ones, so
--show-all would be a better name for it.)
--undef-value-errors=<yes|no> [default: yes]
Controls whether Memcheck reports uses of undefined value
errors. Set this to no if you don't want to see undefined value
errors. It also has the side effect of speeding up Memcheck
somewhat.
--track-origins=<yes|no> [default: no]
Controls whether Memcheck tracks the origin of uninitialised
values. By default, it does not, which means that although it
can tell you that an uninitialised value is being used in a
dangerous way, it cannot tell you where the uninitialised value
came from. This often makes it difficult to track down the root
problem.
When set to yes, Memcheck keeps track of the origins of all
uninitialised values. Then, when an uninitialised value error is
reported, Memcheck will try to show the origin of the value. An
origin can be one of the following four places: a heap block, a
stack allocation, a client request, or miscellaneous other
sources (eg, a call to brk).
For uninitialised values originating from a heap block, Memcheck
shows where the block was allocated. For uninitialised values
originating from a stack allocation, Memcheck can tell you which
function allocated the value, but no more than that -- typically
it shows you the source location of the opening brace of the
function. So you should carefully check that all of the
function's local variables are initialised properly.
Performance overhead: origin tracking is expensive. It halves
Memcheck's speed and increases memory use by a minimum of 100MB,
and possibly more. Nevertheless it can drastically reduce the
effort required to identify the root cause of uninitialised
value errors, and so is often a programmer productivity win,
despite running more slowly.
Accuracy: Memcheck tracks origins quite accurately. To avoid
very large space and time overheads, some approximations are
made. It is possible, although unlikely, that Memcheck will
report an incorrect origin, or not be able to identify any
origin.
Note that the combination --track-origins=yes and
--undef-value-errors=no is nonsensical. Memcheck checks for and
rejects this combination at startup.
--partial-loads-ok=<yes|no> [default: no]
Controls how Memcheck handles word-sized, word-aligned loads
from addresses for which some bytes are addressable and others
are not. When yes, such loads do not produce an address error.
Instead, loaded bytes originating from illegal addresses are
marked as uninitialised, and those corresponding to legal
addresses are handled in the normal way.
When no, loads from partially invalid addresses are treated the
same as loads from completely invalid addresses: an
illegal-address error is issued, and the resulting bytes are
marked as initialised.
Note that code that behaves in this way is in violation of the
the ISO C/C++ standards, and should be considered broken. If at
all possible, such code should be fixed. This option should be
used only as a last resort.
--freelist-vol=<number> [default: 10000000]
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 ten 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.
--workaround-gcc296-bugs=<yes|no> [default: no]
When enabled, assume that reads and writes some small distance
below the stack pointer are due to bugs in GCC 2.96, and does
not report them. The "small distance" is 256 bytes by default.
Note that GCC 2.96 is the default compiler on some ancient Linux
distributions (RedHat 7.X) and so you may need to use this
option. Do not use it if you do not have to, as it can cause
real errors to be overlooked. A better alternative is to use a
more recent GCC in which this bug is fixed.
You may also need to use this option when working with GCC 3.X
or 4.X on 32-bit PowerPC Linux. This is because GCC generates
code which occasionally accesses below the stack pointer,
particularly for floating-point to/from integer conversions.
This is in violation of the 32-bit PowerPC ELF specification,
which makes no provision for locations below the stack pointer
to be accessible.
--ignore-ranges=0xPP-0xQQ[,0xRR-0xSS]
Any ranges listed in this option (and multiple ranges can be
specified, separated by commas) will be ignored by Memcheck's
addressability checking.
--malloc-fill=<hexnumber>
Fills blocks allocated by malloc, new, etc, but not by calloc,
with the specified byte. This can be useful when trying to shake
out obscure memory corruption problems. The allocated area is
still regarded by Memcheck as undefined -- this option only
affects its contents.
--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.
CACHEGRIND OPTIONS
--I1=<size>,<associativity>,<line size>
Specify the size, associativity and line size of the level 1
instruction cache.
--D1=<size>,<associativity>,<line size>
Specify the size, associativity and line size of the level 1
data cache.
--L2=<size>,<associativity>,<line size>
Specify the size, associativity and line size of the level 2
cache.
--cache-sim=no|yes [yes]
Enables or disables collection of cache access and miss counts.
--branch-sim=no|yes [no]
Enables or disables collection of branch instruction and
misprediction counts. By default this is disabled as it slows
Cachegrind down by approximately 25%. Note that you cannot
specify --cache-sim=no and --branch-sim=no together, as that
would leave Cachegrind with no information to collect.
--cachegrind-out-file=<file>
Write the profile data to file rather than to the default output
file, cachegrind.out.<pid>. The %p and %q format specifiers can
be used to embed the process ID and/or the contents of an
environment variable in the name, as is the case for the core
option --log-file.
CALLGRIND OPTIONS
--callgrind-out-file=<file>
Write the profile data to file rather than to the default output
file, callgrind.out.<pid>. The %p and %q format specifiers can
be used to embed the process ID and/or the contents of an
environment variable in the name, as is the case for the core
option --log-file. When multiple dumps are made, the file name
is modified further; see below.
--dump-line=<no|yes> [default: yes]
This specifies that event counting should be performed at source
line granularity. This allows source annotation for sources
which are compiled with debug information (-g).
--dump-instr=<no|yes> [default: no]
This specifies that event counting should be performed at
per-instruction granularity. This allows for assembly code
annotation. Currently the results can only be displayed by
KCachegrind.
--compress-strings=<no|yes> [default: yes]
This option influences the output format of the profile data. It
specifies whether strings (file and function names) should be
identified by numbers. This shrinks the file, but makes it more
difficult for humans to read (which is not recommended in any
case).
--compress-pos=<no|yes> [default: yes]
This option influences the output format of the profile data. It
specifies whether numerical positions are always specified as
absolute values or are allowed to be relative to previous
numbers. This shrinks the file size.
--combine-dumps=<no|yes> [default: no]
When enabled, when multiple profile data parts are to be
generated these parts are appended to the same output file. Not
recommended.
--dump-every-bb=<count> [default: 0, never]
Dump profile data every count basic blocks. Whether a dump is
needed is only checked when Valgrind's internal scheduler is
run. Therefore, the minimum setting useful is about 100000. The
count is a 64-bit value to make long dump periods possible.
--dump-before=<function>
Dump when entering function.
--zero-before=<function>
Zero all costs when entering function.
--dump-after=<function>
Dump when leaving function.
--instr-atstart=<yes|no> [default: yes]
Specify if you want Callgrind to start simulation and profiling
from the beginning of the program. When set to no, Callgrind
will not be able to collect any information, including calls,
but it will have at most a slowdown of around 4, which is the
minimum Valgrind overhead. Instrumentation can be interactively
enabled via callgrind_control -i on.
Note that the resulting call graph will most probably not
contain main, but will contain all the functions executed after
instrumentation was enabled. Instrumentation can also
programatically enabled/disabled. See the Callgrind include file
callgrind.h for the macro you have to use in your source code.
For cache simulation, results will be less accurate when
switching on instrumentation later in the program run, as the
simulator starts with an empty cache at that moment. Switch on
event collection later to cope with this error.
--collect-atstart=<yes|no> [default: yes]
Specify whether event collection is enabled at beginning of the
profile run.
To only look at parts of your program, you have two
possibilities:
1. Zero event counters before entering the program part you want
to profile, and dump the event counters to a file after
leaving that program part.
2. Switch on/off collection state as needed to only see event
counters happening while inside of the program part you want
to profile.
The second option can be used if the program part you want to
profile is called many times. Option 1, i.e. creating a lot of
dumps is not practical here.
Collection state can be toggled at entry and exit of a given
function with the option --toggle-collect. If you use this
option, collection state should be disabled at the beginning.
Note that the specification of --toggle-collect implicitly sets
--collect-state=no.
Collection state can be toggled also by inserting the client
request CALLGRIND_TOGGLE_COLLECT ; at the needed code positions.
--toggle-collect=<function>
Toggle collection on entry/exit of function.
--collect-jumps=<no|yes> [default: no]
This specifies whether information for (conditional) jumps
should be collected. As above, callgrind_annotate currently is
not able to show you the data. You have to use KCachegrind to
get jump arrows in the annotated code.
--collect-systime=<no|yes> [default: no]
This specifies whether information for system call times should
be collected.
--simulate-cache=<yes|no> [default: no]
Specify if you want to do full cache simulation. By default,
only instruction read accesses will be profiled.
--simulate-wb=<yes|no> [default: no]
Specify whether write-back behavior should be simulated,
allowing to distinguish L2 caches misses with and without write
backs. The cache model of Cachegrind/Callgrind does not specify
write-through vs. write-back behavior, and this also is not
relevant for the number of generated miss counts. However, with
explicit write-back simulation it can be decided whether a miss
triggers not only the loading of a new cache line, but also if a
write back of a dirty cache line had to take place before. The
new dirty miss events are I2dmr, D2dmr, and D2dmw, for misses
because of instruction read, data read, and data write,
respectively. As they produce two memory transactions, they
should account for a doubled time estimation in relation to a
normal miss.
--simulate-hwpref=<yes|no> [default: no]
Specify whether simulation of a hardware prefetcher should be
added which is able to detect stream access in the second level
cache by comparing accesses to separate to each page. As the
simulation can not decide about any timing issues of
prefetching, it is assumed that any hardware prefetch triggered
succeeds before a real access is done. Thus, this gives a
best-case scenario by covering all possible stream accesses.
--cacheuse=<yes|no> [default: no]
Specify whether cache line use should be collected. For every
cache line, from loading to it being evicted, the number of
accesses as well as the number of actually used bytes is
determined. This behavior is related to the code which triggered
loading of the cache line. In contrast to miss counters, which
shows the position where the symptoms of bad cache behavior
(i.e. latencies) happens, the use counters try to pinpoint at
the reason (i.e. the code with the bad access behavior). The new
counters are defined in a way such that worse behavior results
in higher cost. AcCost1 and AcCost2 are counters showing bad
temporal locality for L1 and L2 caches, respectively. This is
done by summing up reciprocal values of the numbers of accesses
of each cache line, multiplied by 1000 (as only integer costs
are allowed). E.g. for a given source line with 5 read accesses,
a value of 5000 AcCost means that for every access, a new cache
line was loaded and directly evicted afterwards without further
accesses. Similarly, SpLoss1/2 shows bad spatial locality for L1
and L2 caches, respectively. It gives the spatial loss count of
bytes which were loaded into cache but never accessed. It
pinpoints at code accessing data in a way such that cache space
is wasted. This hints at bad layout of data structures in
memory. Assuming a cache line size of 64 bytes and 100 L1 misses
for a given source line, the loading of 6400 bytes into L1 was
triggered. If SpLoss1 shows a value of 3200 for this line, this
means that half of the loaded data was never used, or using a
better data layout, only half of the cache space would have been
needed. Please note that for cache line use counters, it
currently is not possible to provide meaningful inclusive costs.
Therefore, inclusive cost of these counters should be ignored.
--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.
--L2=<size>,<associativity>,<line size>
Specify the size, associativity and line size of the level 2
cache.
HELGRIND OPTIONS
--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.
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.
DRD OPTIONS
--check-stack-var=<yes|no> [default: no]
Controls whether DRD detects data races on stack variables.
Verifying stack variables is disabled by default because most
programs do not share stack variables over threads.
--exclusive-threshold=<n> [default: off]
Print an error message if any mutex or writer lock has been held
longer than the time specified in milliseconds. This option
enables the detection of lock contention.
--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.
--report-signal-unlocked=<yes|no> [default: yes]
Whether to report calls to pthread_cond_signal and
pthread_cond_broadcast where the mutex associated with the
signal through pthread_cond_wait or pthread_cond_timed_waitis
not locked at the time the signal is sent. Sending a signal
without holding a lock on the associated mutex is a common
programming error which can cause subtle race conditions and
unpredictable behavior. There exist some uncommon
synchronization patterns however where it is safe to send a
signal without holding a lock on the associated mutex.
--segment-merging=<yes|no> [default: yes]
Controls segment merging. Segment merging is an algorithm to
limit memory usage of the data race detection algorithm.
Disabling segment merging may improve the accuracy of the
so-called 'other segments' displayed in race reports but can
also trigger an out of memory error.
--segment-merging-interval=<n> [default: 10]
Perform segment merging only after the specified number of new
segments have been created. This is an advanced configuration
option that allows to choose whether to minimize DRD's memory
usage by choosing a low value or to let DRD run faster by
choosing a slightly higher value. The optimal value for this
parameter depends on the program being analyzed. The default
value works well for most programs.
--shared-threshold=<n> [default: off]
Print an error message if a reader lock has been held longer
than the specified time (in milliseconds). This option enables
the detection of lock contention.
--show-confl-seg=<yes|no> [default: yes]
Show conflicting segments in race reports. Since this
information can help to find the cause of a data race, this
option is enabled by default. Disabling this option makes the
output of DRD more compact.
--show-stack-usage=<yes|no> [default: no]
Print stack usage at thread exit time. When a program creates a
large number of threads it becomes important to limit the amount
of virtual memory allocated for thread stacks. This option makes
it possible to observe how much stack memory has been used by
each thread of the the client program. Note: the DRD tool itself
allocates some temporary data on the client thread stack. The
space necessary for this temporary data must be allocated by the
client program when it allocates stack memory, but is not
included in stack usage reported by DRD.
--trace-addr=<address> [default: none]
Trace all load and store activity for the specified address.
This option may be specified more than once.
--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-mutex=<yes|no> [default: no]
Trace all mutex activity.
--trace-rwlock=<yes|no> [default: no]
Trace all reader-writer lock activity.
--trace-semaphore=<yes|no> [default: no]
Trace all semaphore activity.
MASSIF OPTIONS
--heap=<yes|no> [default: yes]
Specifies whether heap profiling should be done.
--heap-admin=<size> [default: 8]
If heap profiling is enabled, gives the number of administrative
bytes per block to use. This should be an estimate of the
average, since it may vary. For example, the allocator used by
glibc on Linux requires somewhere between 4 to 15 bytes per
block, depending on various factors. That allocator also
requires admin space for freed blocks, but Massif cannot account
for this.
--stacks=<yes|no> [default: yes]
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.
--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.
PTRCHECK OPTIONS
--enable-sg-checks=no|yes [default: yes]
By default, Ptrcheck checks for overruns of stack, global and
heap arrays. With --enable-sg-checks=no, the stack and global
array checks are omitted, and only heap checking is performed.
This can be useful because the stack and global checks are quite
expensive, so omitting them speeds Ptrcheck up a lot.
--partial-loads-ok=<yes|no> [default: no]
This option has the same meaning as it does for Memcheck.
Controls how Ptrcheck handles word-sized, word-aligned loads
which partially overlap the end of heap blocks -- that is, some
of the bytes in the word are validly addressable, but others are
not. When yes, such loads do not produce an address error. When
no (the default), loads from partially invalid addresses are
treated the same as loads from completely invalid addresses: an
illegal heap access error is issued.
Note that code that behaves in this way is in violation of the
the ISO C/C++ standards, and should be considered broken. If at
all possible, such code should be fixed. This option should be
used only as a last resort.
BBV OPTIONS
--bb-out-file=<name> [default: bb.out.%p]
This option selects the name of the basic block vector file. The
%p and %q format specifiers can be used to embed the process ID
and/or the contents of an environment variable in the name, as
is the case for the core option --log-file.
--pc-out-file=<name> [default: pc.out.%p]
This option selects the name of the PC file. This file holds
program counter addresses and function name info for the various
basic blocks. This can be used in conjunction with the basic
block vector file to fast-forward via function names instead of
just instruction counts. The %p and %q format specifiers can be
used to embed the process ID and/or the contents of an
environment variable in the name, as is the case for the core
option --log-file.
--interval-size=<number> [default: 100000000]
This option selects the size of the interval to use. The default
is 100 million instructions, which is a commonly used value.
Other sizes can be used; smaller intervals can help programs
with finer-grained phases. However smaller interval size can
lead to accuracy issues due to warm-up effects (When
fast-forwarding the various architectural features will be
un-initialized, and it will take some number of instructions
before they "warm up" to the state a full simulation would be at
without the fast-forwarding. Large interval sizes tend to
mitigate this.)
--instr-count-only [default: no]
This option tells the tool to only display instruction count
totals, and to not generate the actual basic block vector file.
This is useful for debugging, and for gathering instruction
count info without generating the large basic block vector
files.
LACKEY OPTIONS
--basic-counts=<no|yes> [default: yes]
When enabled, Lackey prints the following statistics and
information about the execution of the client program:
1. The number of calls to the function specified by the --fnname
option (the default is main). If the program has had its
symbols stripped, the count will always be zero.
2. The number of conditional branches encountered and the number
and proportion of those taken.
3. The number of superblocks entered and completed by the
program. Note that due to optimisations done by the JIT, this
is not at all an accurate value.
4. The number of guest (x86, amd64, ppc, etc.) instructions and
IR statements executed. IR is Valgrind's RISC-like
intermediate representation via which all instrumentation is
done.
5. Ratios between some of these counts.
6. The exit code of the client program.
--detailed-counts=<no|yes> [default: no]
When enabled, Lackey prints a table containing counts of loads,
stores and ALU operations, differentiated by their IR types. The
IR types are identified by their IR name ("I1", "I8", ...
"I128", "F32", "F64", and "V128").
--trace-mem=<no|yes> [default: no]
When enabled, Lackey prints the size and address of almost every
memory access made by the program. See the comments at the top
of the file lackey/lk_main.c for details about the output
format, how it works, and inaccuracies in the address trace.
Note that this option produces immense amounts of output.
--trace-superblocks=<no|yes> [default: no]
When enabled, Lackey prints out the address of every superblock
(a single entry, multiple exit, linear chunk of code) executed
by the program. This is primarily of interest to Valgrind
developers. See the comments at the top of the file
lackey/lk_main.c for details about the output format. Note that
this option produces large amounts of output.
--fnname=<name> [default: main]
Changes the function for which calls are counted when
--basic-counts=yes is specified.
SEE ALSOcg_annotate(1), callgrind_annotate(1), callgrind_control(1),
ms_print(1), $INSTALL/share/doc/valgrind/html/index.html or
http://www.valgrind.org/docs/manual/index.html.
AUTHOR
The Valgrind developers.
This manpage was written by Andres Roldan <aroldan@debian.org> and the
Valgrind developers.
Release 3.5.0 08/19/2009 VALGRIND(1)
