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| <chapter id="manual-core" xreflabel="Valgrind's core"> |
| <title>Using and understanding the Valgrind core</title> |
| |
| <para>This chapter describes the Valgrind core services, flags and |
| behaviours. That means it is relevant regardless of what particular |
| tool you are using. The information should be sufficient for you to |
| make effective day-to-day use of Valgrind. Advanced topics related to |
| the Valgrind core are described in <xref linkend="manual-core-adv"/>. |
| </para> |
| |
| <para> |
| A point of terminology: most references to "Valgrind" in this chapter |
| refer to the Valgrind core services. </para> |
| |
| |
| |
| <sect1 id="manual-core.whatdoes" |
| xreflabel="What Valgrind does with your program"> |
| <title>What Valgrind does with your program</title> |
| |
| <para>Valgrind is designed to be as non-intrusive as possible. It works |
| directly with existing executables. You don't need to recompile, relink, |
| or otherwise modify, the program to be checked.</para> |
| |
| <para>Simply put |
| <computeroutput>valgrind --tool=tool_name</computeroutput> |
| at the start of the command line normally used to run the program. For |
| example, if want to run the command |
| <computeroutput>ls -l</computeroutput> using the heavyweight |
| memory-checking tool Memcheck, issue the command:</para> |
| |
| <programlisting><![CDATA[ |
| valgrind --tool=memcheck ls -l]]></programlisting> |
| |
| <para>Memcheck is the default, so if you want to use it you can |
| omit the <option>--tool</option> flag.</para> |
| |
| <para>Regardless of which tool is in use, Valgrind takes control of your |
| program before it starts. Debugging information is read from the |
| executable and associated libraries, so that error messages and other |
| outputs can be phrased in terms of source code locations, when |
| appropriate.</para> |
| |
| <para>Your program is then run on a synthetic CPU provided by the |
| Valgrind core. As new code is executed for the first time, the core |
| hands the code to the selected tool. The tool adds its own |
| instrumentation code to this and hands the result back to the core, |
| which coordinates the continued execution of this instrumented |
| code.</para> |
| |
| <para>The amount of instrumentation code added varies widely between |
| tools. At one end of the scale, Memcheck adds code to check every |
| memory access and every value computed, |
| making it run 10-50 times slower than natively. |
| At the other end of the spectrum, the ultra-trivial "none" tool |
| (also referred to as Nulgrind) adds no instrumentation at all |
| and causes in total |
| "only" about a 4 times slowdown.</para> |
| |
| <para>Valgrind simulates every single instruction your program executes. |
| Because of this, the active tool checks, or profiles, not only the code |
| in your application but also in all supporting dynamically-linked |
| (<computeroutput>.so</computeroutput>-format) libraries, including the |
| GNU C library, the X client libraries, Qt, if you work with KDE, and so |
| on.</para> |
| |
| <para>If you're using an error-detection tool, Valgrind may |
| detect errors in libraries, for example the GNU C or X11 |
| libraries, which you have to use. You might not be interested in these |
| errors, since you probably have no control over that code. Therefore, |
| Valgrind allows you to selectively suppress errors, by recording them in |
| a suppressions file which is read when Valgrind starts up. The build |
| mechanism attempts to select suppressions which give reasonable |
| behaviour for the C library |
| and X11 client library versions detected on your machine. |
| To make it easier to write suppressions, you can use the |
| <option>--gen-suppressions=yes</option> option. This tells Valgrind to |
| print out a suppression for each reported error, which you can then |
| copy into a suppressions file.</para> |
| |
| <para>Different error-checking tools report different kinds of errors. |
| The suppression mechanism therefore allows you to say which tool or |
| tool(s) each suppression applies to.</para> |
| |
| </sect1> |
| |
| |
| <sect1 id="manual-core.started" xreflabel="Getting started"> |
| <title>Getting started</title> |
| |
| <para>First off, consider whether it might be beneficial to recompile |
| your application and supporting libraries with debugging info enabled |
| (the <option>-g</option> flag). Without debugging info, the best |
| Valgrind tools will be able to do is guess which function a particular |
| piece of code belongs to, which makes both error messages and profiling |
| output nearly useless. With <option>-g</option>, you'll get |
| messages which point directly to the relevant source code lines.</para> |
| |
| <para>Another flag you might like to consider, if you are working with |
| C++, is <option>-fno-inline</option>. That makes it easier to see the |
| function-call chain, which can help reduce confusion when navigating |
| around large C++ apps. For example, debugging |
| OpenOffice.org with Memcheck is a bit easier when using this flag. You |
| don't have to do this, but doing so helps Valgrind produce more accurate |
| and less confusing error reports. Chances are you're set up like this |
| already, if you intended to debug your program with GNU gdb, or some |
| other debugger.</para> |
| |
| <para>If you are planning to use Memcheck: On rare |
| occasions, compiler optimisations (at <computeroutput>-O2</computeroutput> |
| and above, and sometimes <computeroutput>-O1</computeroutput>) have been |
| observed to generate code which fools Memcheck into wrongly reporting |
| uninitialised value errors, or missing uninitialised value errors. We have |
| looked in detail into fixing this, and unfortunately the result is that |
| doing so would give a further significant slowdown in what is already a slow |
| tool. So the best solution is to turn off optimisation altogether. Since |
| this often makes things unmanageably slow, a reasonable compromise is to use |
| <computeroutput>-O</computeroutput>. This gets you the majority of the |
| benefits of higher optimisation levels whilst keeping relatively small the |
| chances of false positives or false negatives from Memcheck. Also, you |
| should compile your code with <computeroutput>-Wall</computeroutput> because |
| it can identify some or all of the problems that Valgrind can miss at the |
| higher optimisation levels. (Using <computeroutput>-Wall</computeroutput> |
| is also a good idea in general.) All other tools (as far as we know) are |
| unaffected by optimisation level.</para> |
| |
| <para>Valgrind understands both the older "stabs" debugging format, used |
| by gcc versions prior to 3.1, and the newer DWARF2 and DWARF3 formats |
| used by gcc |
| 3.1 and later. We continue to develop our debug-info readers, |
| although the majority of effort will naturally enough go into the newer |
| DWARF2/3 reader.</para> |
| |
| <para>When you're ready to roll, just run your application as you |
| would normally, but place |
| <computeroutput>valgrind --tool=tool_name</computeroutput> in front of |
| your usual command-line invocation. Note that you should run the real |
| (machine-code) executable here. If your application is started by, for |
| example, a shell or perl script, you'll need to modify it to invoke |
| Valgrind on the real executables. Running such scripts directly under |
| Valgrind will result in you getting error reports pertaining to |
| <computeroutput>/bin/sh</computeroutput>, |
| <computeroutput>/usr/bin/perl</computeroutput>, or whatever interpreter |
| you're using. This may not be what you want and can be confusing. You |
| can force the issue by giving the flag |
| <option>--trace-children=yes</option>, but confusion is still |
| likely.</para> |
| |
| </sect1> |
| |
| |
| <sect1 id="manual-core.comment" xreflabel="The Commentary"> |
| <title>The Commentary</title> |
| |
| <para>Valgrind tools write a commentary, a stream of text, detailing |
| error reports and other significant events. All lines in the commentary |
| have following form: |
| |
| <programlisting><![CDATA[ |
| ==12345== some-message-from-Valgrind]]></programlisting> |
| </para> |
| |
| <para>The <computeroutput>12345</computeroutput> is the process ID. |
| This scheme makes it easy to distinguish program output from Valgrind |
| commentary, and also easy to differentiate commentaries from different |
| processes which have become merged together, for whatever reason.</para> |
| |
| <para>By default, Valgrind tools write only essential messages to the |
| commentary, so as to avoid flooding you with information of secondary |
| importance. If you want more information about what is happening, |
| re-run, passing the <option>-v</option> flag to Valgrind. A second |
| <option>-v</option> gives yet more detail. |
| </para> |
| |
| <para>You can direct the commentary to three different places:</para> |
| |
| <orderedlist> |
| |
| <listitem id="manual-core.out2fd" xreflabel="Directing output to fd"> |
| <para>The default: send it to a file descriptor, which is by default |
| 2 (stderr). So, if you give the core no options, it will write |
| commentary to the standard error stream. If you want to send it to |
| some other file descriptor, for example number 9, you can specify |
| <option>--log-fd=9</option>.</para> |
| |
| <para>This is the simplest and most common arrangement, but can |
| cause problems when Valgrinding entire trees of processes which |
| expect specific file descriptors, particularly stdin/stdout/stderr, |
| to be available for their own use.</para> |
| </listitem> |
| |
| <listitem id="manual-core.out2file" |
| xreflabel="Directing output to file"> <para>A less intrusive |
| option is to write the commentary to a file, which you specify by |
| <option>--log-file=filename</option>. There are special format |
| specifiers that can be used to use a process ID or an environment |
| variable name in the log file name. These are useful/necessary if your |
| program invokes multiple processes (especially for MPI programs). |
| See the <link linkend="manual-core.basicopts">basic options section</link> |
| for more details.</para> |
| </listitem> |
| |
| <listitem id="manual-core.out2socket" |
| xreflabel="Directing output to network socket"> <para>The |
| least intrusive option is to send the commentary to a network |
| socket. The socket is specified as an IP address and port number |
| pair, like this: <option>--log-socket=192.168.0.1:12345</option> if |
| you want to send the output to host IP 192.168.0.1 port 12345 |
| (note: we |
| have no idea if 12345 is a port of pre-existing significance). You |
| can also omit the port number: |
| <option>--log-socket=192.168.0.1</option>, in which case a default |
| port of 1500 is used. This default is defined by the constant |
| <computeroutput>VG_CLO_DEFAULT_LOGPORT</computeroutput> in the |
| sources.</para> |
| |
| <para>Note, unfortunately, that you have to use an IP address here, |
| rather than a hostname.</para> |
| |
| <para>Writing to a network socket is pointless if you don't |
| have something listening at the other end. We provide a simple |
| listener program, |
| <computeroutput>valgrind-listener</computeroutput>, which accepts |
| connections on the specified port and copies whatever it is sent to |
| stdout. Probably someone will tell us this is a horrible security |
| risk. It seems likely that people will write more sophisticated |
| listeners in the fullness of time.</para> |
| |
| <para>valgrind-listener can accept simultaneous connections from up |
| to 50 Valgrinded processes. In front of each line of output it |
| prints the current number of active connections in round |
| brackets.</para> |
| |
| <para>valgrind-listener accepts two command-line flags:</para> |
| <itemizedlist> |
| <listitem> |
| <para><option>-e</option> or <option>--exit-at-zero</option>: |
| when the number of connected processes falls back to zero, |
| exit. Without this, it will run forever, that is, until you |
| send it Control-C.</para> |
| </listitem> |
| <listitem> |
| <para><option>portnumber</option>: changes the port it listens |
| on from the default (1500). The specified port must be in the |
| range 1024 to 65535. The same restriction applies to port |
| numbers specified by a <option>--log-socket</option> to |
| Valgrind itself.</para> |
| </listitem> |
| </itemizedlist> |
| |
| <para>If a Valgrinded process fails to connect to a listener, for |
| whatever reason (the listener isn't running, invalid or unreachable |
| host or port, etc), Valgrind switches back to writing the commentary |
| to stderr. The same goes for any process which loses an established |
| connection to a listener. In other words, killing the listener |
| doesn't kill the processes sending data to it.</para> |
| </listitem> |
| |
| </orderedlist> |
| |
| <para>Here is an important point about the relationship between the |
| commentary and profiling output from tools. The commentary contains a |
| mix of messages from the Valgrind core and the selected tool. If the |
| tool reports errors, it will report them to the commentary. However, if |
| the tool does profiling, the profile data will be written to a file of |
| some kind, depending on the tool, and independent of what |
| <option>--log-*</option> options are in force. The commentary is |
| intended to be a low-bandwidth, human-readable channel. Profiling data, |
| on the other hand, is usually voluminous and not meaningful without |
| further processing, which is why we have chosen this arrangement.</para> |
| |
| </sect1> |
| |
| |
| <sect1 id="manual-core.report" xreflabel="Reporting of errors"> |
| <title>Reporting of errors</title> |
| |
| <para>When an error-checking tool |
| detects something bad happening in the program, an error |
| message is written to the commentary. Here's an example from Memcheck:</para> |
| |
| <programlisting><![CDATA[ |
| ==25832== Invalid read of size 4 |
| ==25832== at 0x8048724: BandMatrix::ReSize(int, int, int) (bogon.cpp:45) |
| ==25832== by 0x80487AF: main (bogon.cpp:66) |
| ==25832== Address 0xBFFFF74C is not stack'd, malloc'd or free'd]]></programlisting> |
| |
| <para>This message says that the program did an illegal 4-byte read of |
| address 0xBFFFF74C, which, as far as Memcheck can tell, is not a valid |
| stack address, nor corresponds to any current malloc'd or free'd |
| blocks. The read is happening at line 45 of |
| <filename>bogon.cpp</filename>, called from line 66 of the same file, |
| etc. For errors associated with an identified malloc'd/free'd block, |
| for example reading free'd memory, Valgrind reports not only the |
| location where the error happened, but also where the associated block |
| was malloc'd/free'd.</para> |
| |
| <para>Valgrind remembers all error reports. When an error is detected, |
| it is compared against old reports, to see if it is a duplicate. If so, |
| the error is noted, but no further commentary is emitted. This avoids |
| you being swamped with bazillions of duplicate error reports.</para> |
| |
| <para>If you want to know how many times each error occurred, run with |
| the <option>-v</option> option. When execution finishes, all the |
| reports are printed out, along with, and sorted by, their occurrence |
| counts. This makes it easy to see which errors have occurred most |
| frequently.</para> |
| |
| <para>Errors are reported before the associated operation actually |
| happens. If you're using a tool (eg. Memcheck) which does |
| address checking, and your program attempts to read from address zero, |
| the tool will emit a message to this effect, and the program will then |
| duly die with a segmentation fault.</para> |
| |
| <para>In general, you should try and fix errors in the order that they |
| are reported. Not doing so can be confusing. For example, a program |
| which copies uninitialised values to several memory locations, and later |
| uses them, will generate several error messages, when run on Memcheck. |
| The first such error message may well give the most direct clue to the |
| root cause of the problem.</para> |
| |
| <para>The process of detecting duplicate errors is quite an |
| expensive one and can become a significant performance overhead |
| if your program generates huge quantities of errors. To avoid |
| serious problems, Valgrind will simply stop collecting |
| errors after 1,000 different errors have been seen, or 10,000,000 errors |
| in total have been seen. In this situation you might as well |
| stop your program and fix it, because Valgrind won't tell you |
| anything else useful after this. Note that the 1,000/10,000,000 limits |
| apply after suppressed errors are removed. These limits are |
| defined in <filename>m_errormgr.c</filename> and can be increased |
| if necessary.</para> |
| |
| <para>To avoid this cutoff you can use the |
| <option>--error-limit=no</option> flag. Then Valgrind will always show |
| errors, regardless of how many there are. Use this flag carefully, |
| since it may have a bad effect on performance.</para> |
| |
| </sect1> |
| |
| |
| <sect1 id="manual-core.suppress" xreflabel="Suppressing errors"> |
| <title>Suppressing errors</title> |
| |
| <para>The error-checking tools detect numerous problems in the base |
| libraries, such as the GNU C library, and the X11 client libraries, |
| which come pre-installed on your GNU/Linux system. You can't easily fix |
| these, but you don't want to see these errors (and yes, there are many!) |
| So Valgrind reads a list of errors to suppress at startup. A default |
| suppression file is created by the |
| <computeroutput>./configure</computeroutput> script when the system is |
| built.</para> |
| |
| <para>You can modify and add to the suppressions file at your leisure, |
| or, better, write your own. Multiple suppression files are allowed. |
| This is useful if part of your project contains errors you can't or |
| don't want to fix, yet you don't want to continuously be reminded of |
| them.</para> |
| |
| <formalpara><title>Note:</title> <para>By far the easiest way to add |
| suppressions is to use the <option>--gen-suppressions=yes</option> flag |
| described in <xref linkend="manual-core.flags"/>.</para> |
| </formalpara> |
| |
| <para>Each error to be suppressed is described very specifically, to |
| minimise the possibility that a suppression-directive inadvertantly |
| suppresses a bunch of similar errors which you did want to see. The |
| suppression mechanism is designed to allow precise yet flexible |
| specification of errors to suppress.</para> |
| |
| <para>If you use the <option>-v</option> flag, at the end of execution, |
| Valgrind prints out one line for each used suppression, giving its name |
| and the number of times it got used. Here's the suppressions used by a |
| run of <computeroutput>valgrind --tool=memcheck ls -l</computeroutput>:</para> |
| |
| <programlisting><![CDATA[ |
| --27579-- supp: 1 socketcall.connect(serv_addr)/__libc_connect/__nscd_getgrgid_r |
| --27579-- supp: 1 socketcall.connect(serv_addr)/__libc_connect/__nscd_getpwuid_r |
| --27579-- supp: 6 strrchr/_dl_map_object_from_fd/_dl_map_object]]></programlisting> |
| |
| <para>Multiple suppressions files are allowed. By default, Valgrind |
| uses <filename>$PREFIX/lib/valgrind/default.supp</filename>. You can |
| ask to add suppressions from another file, by specifying |
| <option>--suppressions=/path/to/file.supp</option>. |
| </para> |
| |
| <para>If you want to understand more about suppressions, look at an |
| existing suppressions file whilst reading the following documentation. |
| The file <filename>glibc-2.3.supp</filename>, in the source |
| distribution, provides some good examples.</para> |
| |
| <para>Each suppression has the following components:</para> |
| |
| <itemizedlist> |
| |
| <listitem> |
| <para>First line: its name. This merely gives a handy name to the |
| suppression, by which it is referred to in the summary of used |
| suppressions printed out when a program finishes. It's not |
| important what the name is; any identifying string will do.</para> |
| </listitem> |
| |
| <listitem> |
| <para>Second line: name of the tool(s) that the suppression is for |
| (if more than one, comma-separated), and the name of the suppression |
| itself, separated by a colon (n.b.: no spaces are allowed), eg:</para> |
| <programlisting><![CDATA[ |
| tool_name1,tool_name2:suppression_name]]></programlisting> |
| |
| <para>Recall that Valgrind is a modular system, in which |
| different instrumentation tools can observe your program whilst it |
| is running. Since different tools detect different kinds of errors, |
| it is necessary to say which tool(s) the suppression is meaningful |
| to.</para> |
| |
| <para>Tools will complain, at startup, if a tool does not understand |
| any suppression directed to it. Tools ignore suppressions which are |
| not directed to them. As a result, it is quite practical to put |
| suppressions for all tools into the same suppression file.</para> |
| </listitem> |
| |
| <listitem> |
| <para>Next line: a small number of suppression types have extra |
| information after the second line (eg. the <varname>Param</varname> |
| suppression for Memcheck)</para> |
| </listitem> |
| |
| <listitem> |
| <para>Remaining lines: This is the calling context for the error -- |
| the chain of function calls that led to it. There can be up to 24 |
| of these lines.</para> |
| |
| <para>Locations may be either names of shared objects/executables or |
| wildcards matching function names. They begin |
| <computeroutput>obj:</computeroutput> and |
| <computeroutput>fun:</computeroutput> respectively. Function and |
| object names to match against may use the wildcard characters |
| <computeroutput>*</computeroutput> and |
| <computeroutput>?</computeroutput>.</para> |
| |
| <para><command>Important note: </command> C++ function names must be |
| <command>mangled</command>. If you are writing suppressions by |
| hand, use the <option>--demangle=no</option> option to get the |
| mangled names in your error messages.</para> |
| </listitem> |
| |
| <listitem> |
| <para>Finally, the entire suppression must be between curly |
| braces. Each brace must be the first character on its own |
| line.</para> |
| </listitem> |
| |
| </itemizedlist> |
| |
| <para>A suppression only suppresses an error when the error matches all |
| the details in the suppression. Here's an example:</para> |
| |
| <programlisting><![CDATA[ |
| { |
| __gconv_transform_ascii_internal/__mbrtowc/mbtowc |
| Memcheck:Value4 |
| fun:__gconv_transform_ascii_internal |
| fun:__mbr*toc |
| fun:mbtowc |
| }]]></programlisting> |
| |
| |
| <para>What it means is: for Memcheck only, suppress a |
| use-of-uninitialised-value error, when the data size is 4, when it |
| occurs in the function |
| <computeroutput>__gconv_transform_ascii_internal</computeroutput>, when |
| that is called from any function of name matching |
| <computeroutput>__mbr*toc</computeroutput>, when that is called from |
| <computeroutput>mbtowc</computeroutput>. It doesn't apply under any |
| other circumstances. The string by which this suppression is identified |
| to the user is |
| <computeroutput>__gconv_transform_ascii_internal/__mbrtowc/mbtowc</computeroutput>.</para> |
| |
| <para>(See <xref linkend="mc-manual.suppfiles"/> for more details |
| on the specifics of Memcheck's suppression kinds.)</para> |
| |
| <para>Another example, again for the Memcheck tool:</para> |
| |
| <programlisting><![CDATA[ |
| { |
| libX11.so.6.2/libX11.so.6.2/libXaw.so.7.0 |
| Memcheck:Value4 |
| obj:/usr/X11R6/lib/libX11.so.6.2 |
| obj:/usr/X11R6/lib/libX11.so.6.2 |
| obj:/usr/X11R6/lib/libXaw.so.7.0 |
| }]]></programlisting> |
| |
| <para>Suppress any size 4 uninitialised-value error which occurs |
| anywhere in <filename>libX11.so.6.2</filename>, when called from |
| anywhere in the same library, when called from anywhere in |
| <filename>libXaw.so.7.0</filename>. The inexact specification of |
| locations is regrettable, but is about all you can hope for, given that |
| the X11 libraries shipped on the Linux distro on which this example |
| was made have had their symbol tables removed.</para> |
| |
| <para>Although the above two examples do not make this clear, you can |
| freely mix <computeroutput>obj:</computeroutput> and |
| <computeroutput>fun:</computeroutput> lines in a suppression.</para> |
| |
| </sect1> |
| |
| |
| <sect1 id="manual-core.flags" |
| xreflabel="Command-line flags for the Valgrind core"> |
| <title>Command-line flags for the Valgrind core</title> |
| |
| <para>As mentioned above, Valgrind's core accepts a common set of flags. |
| The tools also accept tool-specific flags, which are documented |
| separately for each tool.</para> |
| |
| <para>You invoke Valgrind like this:</para> |
| |
| <programlisting><![CDATA[ |
| valgrind [valgrind-options] your-prog [your-prog-options]]]></programlisting> |
| |
| <para>Valgrind's default settings succeed in giving reasonable behaviour |
| in most cases. We group the available options by rough |
| categories.</para> |
| |
| <sect2 id="manual-core.toolopts" xreflabel="Tool-selection option"> |
| <title>Tool-selection option</title> |
| |
| <para>The single most important option.</para> |
| |
| <itemizedlist> |
| <listitem id="tool_name"> |
| <para><option>--tool=<name></option> [default=memcheck]</para> |
| <para>Run the Valgrind tool called <emphasis>name</emphasis>, |
| e.g. Memcheck, Cachegrind, etc.</para> |
| </listitem> |
| </itemizedlist> |
| |
| </sect2> |
| |
| |
| |
| <sect2 id="manual-core.basicopts" xreflabel="Basic Options"> |
| <title>Basic Options</title> |
| |
| <!-- start of xi:include in the manpage --> |
| <para id="basic.opts.para">These options work with all tools.</para> |
| |
| <variablelist id="basic.opts.list"> |
| |
| <varlistentry id="opt.help" xreflabel="--help"> |
| <term><option>-h --help</option></term> |
| <listitem> |
| <para>Show help for all options, both for the core and for the |
| selected tool.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.help-debug" xreflabel="--help-debug"> |
| <term><option>--help-debug</option></term> |
| <listitem> |
| <para>Same as <option>--help</option>, but also lists debugging |
| options which usually are only of use to Valgrind's |
| developers.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.version" xreflabel="--version"> |
| <term><option>--version</option></term> |
| <listitem> |
| <para>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.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.quiet" xreflabel="--quiet"> |
| <term><option>-q --quiet</option></term> |
| <listitem> |
| <para>Run silently, and only print error messages. Useful if you |
| are running regression tests or have some other automated test |
| machinery.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.verbose" xreflabel="--verbose"> |
| <term><option>-v --verbose</option></term> |
| <listitem> |
| <para>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 flag increases the verbosity level.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.d" xreflabel="-d"> |
| <term><option>-d</option></term> |
| <listitem> |
| <para>Emit information for debugging Valgrind itself. This is |
| usually only of interest to the Valgrind developers. Repeating |
| the flag produces more detailed output. If you want to send us a |
| bug report, a log of the output generated by |
| <option>-v -v -d -d</option> will make your report more |
| useful.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.tool" xreflabel="--tool"> |
| <term> |
| <option><![CDATA[--tool=<toolname> [default: memcheck] ]]></option> |
| </term> |
| <listitem> |
| <para>Run the Valgrind tool called <varname>toolname</varname>, |
| e.g. Memcheck, Cachegrind, etc.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.trace-children" xreflabel="--trace-children"> |
| <term> |
| <option><![CDATA[--trace-children=<yes|no> [default: no] ]]></option> |
| </term> |
| <listitem> |
| <para>When enabled, Valgrind will trace into sub-processes |
| initiated via the <varname>exec</varname> system call. This can be |
| confusing and isn't usually what you want, so it is disabled by |
| default. |
| </para> |
| <para>Note that Valgrind does trace into the child of a |
| <varname>fork</varname> (it would be difficult not to, since |
| <varname>fork</varname> makes an identical copy of a process), so this |
| option is arguably badly named. However, most children of |
| <varname>fork</varname> calls immediately call <varname>exec</varname> |
| anyway. |
| </para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.child-silent-after-fork" |
| xreflabel="--child-silent-after-fork"> |
| <term> |
| <option><![CDATA[--child-silent-after-fork=<yes|no> [default: no] ]]></option> |
| </term> |
| <listitem> |
| <para>When enabled, Valgrind will not show any debugging or |
| logging output for the child process resulting from |
| a <varname>fork</varname> 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 <varname>--trace-children=</varname>. Use of this flag is also |
| strongly recommended if you are requesting XML output |
| (<varname>--xml=yes</varname>), since otherwise the XML from child and |
| parent may become mixed up, which usually makes it useless. |
| </para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.track-fds" xreflabel="--track-fds"> |
| <term> |
| <option><![CDATA[--track-fds=<yes|no> [default: no] ]]></option> |
| </term> |
| <listitem> |
| <para>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.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.time-stamp" xreflabel="--time-stamp"> |
| <term> |
| <option><![CDATA[--time-stamp=<yes|no> [default: no] ]]></option> |
| </term> |
| <listitem> |
| <para>When enabled, each message is preceded with an indication of |
| the elapsed wallclock time since startup, expressed as days, |
| hours, minutes, seconds and milliseconds.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.log-fd" xreflabel="--log-fd"> |
| <term> |
| <option><![CDATA[--log-fd=<number> [default: 2, stderr] ]]></option> |
| </term> |
| <listitem> |
| <para>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.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.log-file" xreflabel="--log-file"> |
| <term> |
| <option><![CDATA[--log-file=<filename> ]]></option> |
| </term> |
| <listitem> |
| <para>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.</para> |
| |
| <para><option>%p</option> is replaced with the current process ID. |
| This is very useful for program that invoke multiple processes. |
| WARNING: If you use <option>--trace-children=yes</option> and your |
| program invokes multiple processes and you don't use this specifier |
| (or the <option>%q</option> specifier below), the Valgrind output from |
| all those processes will go into one file, possibly jumbled up, and |
| possibly incomplete.</para> |
| |
| <para><option>%q{FOO}</option> is replaced with the contents of the |
| environment variable <varname>FOO</varname>. If the |
| <option>{FOO}</option> 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 <computeroutput>BPROC_RANK</computeroutput> 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 |
| <option>{</option> and <option>}</option> characters may need to be |
| escaped with a backslash.</para> |
| |
| <para><option>%%</option> is replaced with <option>%</option>.</para> |
| |
| <para>If an <option>%</option> is followed by any other character, it |
| causes an abort.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.log-socket" xreflabel="--log-socket"> |
| <term> |
| <option><![CDATA[--log-socket=<ip-address:port-number> ]]></option> |
| </term> |
| <listitem> |
| <para>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 |
| <computeroutput>valgrind-listener</computeroutput> program. For |
| further details, see |
| <link linkend="manual-core.comment">the commentary</link> |
| in the manual.</para> |
| </listitem> |
| </varlistentry> |
| |
| </variablelist> |
| <!-- end of xi:include in the manpage --> |
| |
| </sect2> |
| |
| |
| <sect2 id="manual-core.erropts" xreflabel="Error-related Options"> |
| <title>Error-related options</title> |
| |
| <!-- start of xi:include in the manpage --> |
| <para id="error-related.opts.para">These options are used by all tools |
| that can report errors, e.g. Memcheck, but not Cachegrind.</para> |
| |
| <variablelist id="error-related.opts.list"> |
| |
| <varlistentry id="opt.xml" xreflabel="--xml"> |
| <term> |
| <option><![CDATA[--xml=<yes|no> [default: no] ]]></option> |
| </term> |
| <listitem> |
| <para>When enabled, output will be in XML format. This is aimed |
| at making life easier for tools that consume Valgrind's output as |
| input, such as GUI front ends. Currently this option only works |
| with Memcheck.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.xml-user-comment" xreflabel="--xml-user-comment"> |
| <term> |
| <option><![CDATA[--xml-user-comment=<string> ]]></option> |
| </term> |
| <listitem> |
| <para>Embeds an extra user comment string at the start of the XML |
| output. Only works when <option>--xml=yes</option> is specified; |
| ignored otherwise.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.demangle" xreflabel="--demangle"> |
| <term> |
| <option><![CDATA[--demangle=<yes|no> [default: yes] ]]></option> |
| </term> |
| <listitem> |
| <para>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.</para> |
| |
| <para>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 |
| suppressions file contents dependent on the state of Valgrind's |
| demangling machinery, and would also be slow and pointless.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.num-callers" xreflabel="--num-callers"> |
| <term> |
| <option><![CDATA[--num-callers=<number> [default: 12] ]]></option> |
| </term> |
| <listitem> |
| <para>By default, Valgrind shows twelve levels of function call |
| names to help you identify program locations. You can change that |
| number with this option. This can help in determining the |
| program's location in deeply-nested call chains. 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.</para> |
| |
| <para>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.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.error-limit" xreflabel="--error-limit"> |
| <term> |
| <option><![CDATA[--error-limit=<yes|no> [default: yes] ]]></option> |
| </term> |
| <listitem> |
| <para>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.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.error-exitcode" xreflabel="--error-exitcode"> |
| <term> |
| <option><![CDATA[--error-exitcode=<number> [default: 0] ]]></option> |
| </term> |
| <listitem> |
| <para>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.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.stack-traces" xreflabel="--show-below-main"> |
| <term> |
| <option><![CDATA[--show-below-main=<yes|no> [default: no] ]]></option> |
| </term> |
| <listitem> |
| <para>By default, stack traces for errors do not show any |
| functions that appear beneath <function>main()</function> |
| (or similar functions such as glibc's |
| <function>__libc_start_main()</function>, if |
| <function>main()</function> is not present in the stack trace); |
| most of the time it's uninteresting C library stuff. If this |
| option is enabled, those entries below <function>main()</function> |
| will be shown.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.suppressions" xreflabel="--suppressions"> |
| <term> |
| <option><![CDATA[--suppressions=<filename> [default: $PREFIX/lib/valgrind/default.supp] ]]></option> |
| </term> |
| <listitem> |
| <para>Specifies an extra file from which to read descriptions of |
| errors to suppress. You may use as many extra suppressions files |
| as you like.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.gen-suppressions" xreflabel="--gen-suppressions"> |
| <term> |
| <option><![CDATA[--gen-suppressions=<yes|no|all> [default: no] ]]></option> |
| </term> |
| <listitem> |
| <para>When set to <varname>yes</varname>, Valgrind will pause |
| after every error shown and print the line: |
| <literallayout> ---- Print suppression ? --- [Return/N/n/Y/y/C/c] ----</literallayout> |
| |
| The prompt's behaviour is the same as for the |
| <option>--db-attach</option> option (see below).</para> |
| |
| <para>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.</para> |
| |
| <para>When set to <varname>all</varname>, Valgrind will print a |
| suppression for every reported error, without querying the |
| user.</para> |
| |
| <para>This option is particularly useful with C++ programs, as it |
| prints out the suppressions with mangled names, as |
| required.</para> |
| |
| <para>Note that the suppressions printed are as specific as |
| possible. You may want to common up similar ones, eg. by adding |
| wildcards to function names. 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 |
| <computeroutput><insert a suppression name |
| here></computeroutput>; the name doesn't really matter, it's |
| only used with the <option>-v</option> option which prints out all |
| used suppression records.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.db-attach" xreflabel="--db-attach"> |
| <term> |
| <option><![CDATA[--db-attach=<yes|no> [default: no] ]]></option> |
| </term> |
| <listitem> |
| <para>When enabled, Valgrind will pause after every error shown |
| and print the line: |
| <literallayout> ---- Attach to debugger ? --- [Return/N/n/Y/y/C/c] ----</literallayout> |
| |
| Pressing <varname>Ret</varname>, or <varname>N Ret</varname> or |
| <varname>n Ret</varname>, causes Valgrind not to start a debugger |
| for this error.</para> |
| |
| <para>Pressing <varname>Y Ret</varname> or |
| <varname>y Ret</varname> 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.</para> |
| |
| <para><varname>C Ret</varname> or <varname>c Ret</varname> causes |
| Valgrind not to start a debugger, and not to ask again.</para> |
| |
| <para><command>Note:</command> <option>--db-attach=yes</option> |
| conflicts with <option>--trace-children=yes</option>. You can't |
| use them together. Valgrind refuses to start up in this |
| situation.</para> |
| |
| <para>May 2002: this is a historical relic which could be easily |
| fixed if it gets in your way. Mail us and complain if this is a |
| problem for you.</para> |
| <para>Nov 2002: if you're sending output to a logfile or to a |
| network socket, I guess this option doesn't make any sense. |
| Caveat emptor.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.db-command" xreflabel="--db-command"> |
| <term> |
| <option><![CDATA[--db-command=<command> [default: gdb -nw %f %p] ]]></option> |
| </term> |
| <listitem> |
| <para>Specify the debugger to use with the |
| <option>--db-attach</option> command. The default debugger is |
| gdb. This option is a template that is expanded by Valgrind at |
| runtime. <literal>%f</literal> is replaced with the executable's |
| file name and <literal>%p</literal> is replaced by the process ID |
| of the executable.</para> |
| |
| <para>This specifies how Valgrind will invoke the debugger. By |
| default it will use whatever GDB is detected at build time, which |
| is usually <computeroutput>/usr/bin/gdb</computeroutput>. Using |
| this command, you can specify some alternative command to invoke |
| the debugger you want to use.</para> |
| |
| <para>The command string given can include one or instances of the |
| <literal>%p</literal> and <literal>%f</literal> expansions. Each |
| instance of <literal>%p</literal> expands to the PID of the |
| process to be debugged and each instance of <literal>%f</literal> |
| expands to the path to the executable for the process to be |
| debugged.</para> |
| |
| <para>Since <computeroutput><command></computeroutput> is likely |
| to contain spaces, you will need to put this entire flag in |
| quotes to ensure it is correctly handled by the shell.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.input-fd" xreflabel="--input-fd"> |
| <term> |
| <option><![CDATA[--input-fd=<number> [default: 0, stdin] ]]></option> |
| </term> |
| <listitem> |
| <para>When using <option>--db-attach=yes</option> or |
| <option>--gen-suppressions=yes</option>, 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.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.max-stackframe" xreflabel="--max-stackframe"> |
| <term> |
| <option><![CDATA[--max-stackframe=<number> [default: 2000000] ]]></option> |
| </term> |
| <listitem> |
| <para>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.</para> |
| |
| <para>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.</para> |
| |
| <para>You should only consider use of this flag if Valgrind's |
| debug output directs you to do so. In that case it will tell you |
| the new threshold you should specify.</para> |
| |
| <para>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 flag, you may wish to consider rewriting your |
| code to allocate on the heap rather than on the stack.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.main-stacksize" xreflabel="--main-stacksize"> |
| <term> |
| <option><![CDATA[--main-stacksize=<number> |
| [default: use current 'ulimit' value] ]]></option> |
| </term> |
| <listitem> |
| <para>Specifies the size of the main thread's stack.</para> |
| |
| <para>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.</para> |
| |
| <para>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.</para> |
| |
| <para>If you need a larger total stack size, |
| use <option>--main-stacksize</option> 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.</para> |
| |
| <para>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.</para> |
| |
| <para><option>--main-stacksize</option> 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.</para> |
| |
| <para>You may need to use both <option>--main-stacksize</option> |
| and <option>--max-stackframe</option> together. It is important |
| to understand that <option>--main-stacksize</option> sets the |
| maximum total stack size, |
| whilst <option>--max-stackframe</option> specifies the largest |
| size of any one stack frame. You will have to work out |
| the <option>--main-stacksize</option> value for yourself |
| (usually, if your applications segfaults). But Valgrind will |
| tell you the needed <option>--max-stackframe</option> size, if |
| necessary.</para> |
| |
| <para>As discussed further in the description |
| of <option>--max-stackframe</option>, 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.</para> |
| </listitem> |
| </varlistentry> |
| |
| </variablelist> |
| <!-- end of xi:include in the manpage --> |
| |
| </sect2> |
| |
| |
| <sect2 id="manual-core.mallocopts" xreflabel="malloc()-related Options"> |
| <title><computeroutput>malloc()</computeroutput>-related Options</title> |
| |
| <!-- start of xi:include in the manpage --> |
| <para id="malloc-related.opts.para">For tools that use their own version of |
| <computeroutput>malloc()</computeroutput> (e.g. Memcheck and |
| Massif), the following options apply.</para> |
| |
| <variablelist id="malloc-related.opts.list"> |
| |
| <varlistentry id="opt.alignment" xreflabel="--alignment"> |
| <term> |
| <option><![CDATA[--alignment=<number> [default: 8] ]]></option> |
| </term> |
| <listitem> |
| <para>By default Valgrind's <function>malloc()</function>, |
| <function>realloc()</function>, etc, return 8-byte aligned |
| addresses. This is standard for most processors. However, some |
| programs might assume that <function>malloc()</function> et al |
| return 16-byte or more aligned memory. The supplied value must be |
| between 8 and 4096 inclusive, and must be a power of two.</para> |
| </listitem> |
| </varlistentry> |
| |
| </variablelist> |
| <!-- end of xi:include in the manpage --> |
| |
| </sect2> |
| |
| |
| <sect2 id="manual-core.rareopts" xreflabel="Uncommon Options"> |
| <title>Uncommon Options</title> |
| |
| <!-- start of xi:include in the manpage --> |
| <para id="uncommon.opts.para">These options apply to all tools, as they |
| affect certain obscure workings of the Valgrind core. Most people won't |
| need to use these.</para> |
| |
| <variablelist id="uncommon.opts.list"> |
| |
| <varlistentry id="opt.run-libc-freeres" xreflabel="--run-libc-freeres"> |
| <term> |
| <option><![CDATA[--run-libc-freeres=<yes|no> [default: yes] ]]></option> |
| </term> |
| <listitem> |
| <para>The GNU C library (<function>libc.so</function>), 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.</para> |
| |
| <para>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 <function>__libc_freeres</function> |
| specifically to make glibc release all memory it has allocated. |
| Memcheck therefore tries to run |
| <function>__libc_freeres</function> at exit.</para> |
| |
| <para>Unfortunately, in some very old versions of glibc, |
| <function>__libc_freeres</function> is sufficiently buggy to cause |
| segmentation faults. This was particularly noticeable on Red Hat |
| 7.1. So this flag is provided in order to inhibit the run of |
| <function>__libc_freeres</function>. If your program seems to run |
| fine on Valgrind, but segfaults at exit, you may find that |
| <option>--run-libc-freeres=no</option> fixes that, although at the |
| cost of possibly falsely reporting space leaks in |
| <filename>libc.so</filename>.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.sim-hints" xreflabel="--sim-hints"> |
| <term> |
| <option><![CDATA[--sim-hints=hint1,hint2,... ]]></option> |
| </term> |
| <listitem> |
| <para>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:</para> |
| <itemizedlist> |
| <listitem> |
| <para><option>lax-ioctls: </option> 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.</para> |
| </listitem> |
| <listitem> |
| <para><option>enable-inner: </option> Enable some special |
| magic needed when the program being run is itself |
| Valgrind.</para> |
| </listitem> |
| </itemizedlist> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.kernel-variant" xreflabel="--kernel-variant"> |
| <term> |
| <option>--kernel-variant=variant1,variant2,...</option> |
| </term> |
| <listitem> |
| <para>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:</para> |
| <itemizedlist> |
| <listitem> |
| <para><option>bproc: </option> 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.</para> |
| </listitem> |
| </itemizedlist> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.show-emwarns" xreflabel="--show-emwarns"> |
| <term> |
| <option><![CDATA[--show-emwarns=<yes|no> [default: no] ]]></option> |
| </term> |
| <listitem> |
| <para>When enabled, Valgrind will emit warnings about its CPU |
| emulation in certain cases. These are usually not |
| interesting.</para> |
| </listitem> |
| </varlistentry> |
| |
| <varlistentry id="opt.smc-check" xreflabel="--smc-check"> |
| <term> |
| <option><![CDATA[--smc-check=<none|stack|all> [default: stack] ]]></option> |
| </term> |
| <listitem> |
| <para>This option controls Valgrind's detection of self-modifying |
| code. Valgrind can do no detection, detect self-modifying code on |
| the stack, or detect self-modifying code anywhere. Note that the |
| default option will catch the vast majority of cases, as far as we |
| know. Running with <varname>all</varname> will slow Valgrind down |
| greatly. Running with <varname>none</varname> will rarely |
| speed things up, since very little code gets put on the stack for |
| most programs.</para> |
| |
| <para>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 x86/Linux |
| and amd64/Linux that you need to use this flag.</para> |
| </listitem> |
| </varlistentry> |
| |
| </variablelist> |
| <!-- end of xi:include in the manpage --> |
| |
| </sect2> |
| |
| |
| <sect2 id="manual-core.debugopts" xreflabel="Debugging Valgrind Options"> |
| <title>Debugging Valgrind Options</title> |
| |
| <!-- start of xi:include in the manpage --> |
| <para id="debug.opts.para">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 |
| <option>--help-debug</option> option.</para> |
| <!-- end of xi:include in the manpage --> |
| |
| </sect2> |
| |
| |
| <sect2 id="manual-core.defopts" xreflabel="Setting default options"> |
| <title>Setting default Options</title> |
| |
| <para>Note that Valgrind also reads options from three places:</para> |
| |
| <orderedlist> |
| <listitem> |
| <para>The file <computeroutput>~/.valgrindrc</computeroutput></para> |
| </listitem> |
| |
| <listitem> |
| <para>The environment variable |
| <computeroutput>$VALGRIND_OPTS</computeroutput></para> |
| </listitem> |
| |
| <listitem> |
| <para>The file <computeroutput>./.valgrindrc</computeroutput></para> |
| </listitem> |
| </orderedlist> |
| |
| <para>These are processed in the given order, before the |
| command-line options. Options processed later override those |
| processed earlier; for example, options in |
| <computeroutput>./.valgrindrc</computeroutput> will take |
| precedence over those in |
| <computeroutput>~/.valgrindrc</computeroutput>. The first two |
| are particularly useful for setting the default tool to |
| use.</para> |
| |
| <para>Any tool-specific options put in |
| <computeroutput>$VALGRIND_OPTS</computeroutput> or the |
| <computeroutput>.valgrindrc</computeroutput> files should be |
| prefixed with the tool name and a colon. For example, if you |
| want Memcheck to always do leak checking, you can put the |
| following entry in <literal>~/.valgrindrc</literal>:</para> |
| |
| <programlisting><![CDATA[ |
| --memcheck:leak-check=yes]]></programlisting> |
| |
| <para>This will be ignored if any tool other than Memcheck is |
| run. Without the <computeroutput>memcheck:</computeroutput> |
| part, this will cause problems if you select other tools that |
| don't understand |
| <computeroutput>--leak-check=yes</computeroutput>.</para> |
| |
| </sect2> |
| |
| </sect1> |
| |
| |
| |
| |
| <sect1 id="manual-core.pthreads" xreflabel="Support for Threads"> |
| <title>Support for Threads</title> |
| |
| <para>Valgrind supports programs which use POSIX pthreads. |
| Getting this to work was technically challenging but it now works |
| well enough for significant threaded applications to run.</para> |
| |
| <para>The main thing to point out is that although Valgrind works |
| with the standard Linux threads library (eg. NPTL or LinuxThreads), it |
| serialises execution so that only one thread is running at a time. This |
| approach avoids the horrible implementation problems of implementing a |
| truly multiprocessor version of Valgrind, but it does mean that threaded |
| apps run only on one CPU, even if you have a multiprocessor |
| machine.</para> |
| |
| <para>Valgrind schedules your program's threads in a round-robin fashion, |
| with all threads having equal priority. It switches threads |
| every 100000 basic blocks (on x86, typically around 600000 |
| instructions), which means you'll get a much finer interleaving |
| of thread executions than when run natively. This in itself may |
| cause your program to behave differently if you have some kind of |
| concurrency, critical race, locking, or similar, bugs. In that case |
| you might consider using Valgrind's Helgrind tool to track them down.</para> |
| |
| <para>Your program will use the native |
| <computeroutput>libpthread</computeroutput>, but not all of its facilities |
| will work. In particular, synchronisation of processes via shared-memory |
| segments will not work. This relies on special atomic instruction sequences |
| which Valgrind does not emulate in a way which works between processes. |
| Unfortunately there's no way for Valgrind to warn when this is happening, |
| and such calls will mostly work. Only when there's a race will |
| it fail. |
| </para> |
| |
| <para>Valgrind also supports direct use of the |
| <computeroutput>clone()</computeroutput> system call, |
| <computeroutput>futex()</computeroutput> and so on. |
| <computeroutput>clone()</computeroutput> is supported where either |
| everything is shared (a thread) or nothing is shared (fork-like); partial |
| sharing will fail. Again, any use of atomic instruction sequences in shared |
| memory between processes will not work reliably. |
| </para> |
| |
| |
| </sect1> |
| |
| <sect1 id="manual-core.signals" xreflabel="Handling of Signals"> |
| <title>Handling of Signals</title> |
| |
| <para>Valgrind has a fairly complete signal implementation. It should be |
| able to cope with any POSIX-compliant use of signals.</para> |
| |
| <para>If you're using signals in clever ways (for example, catching |
| SIGSEGV, modifying page state and restarting the instruction), you're |
| probably relying on precise exceptions. In this case, you will need |
| to use <computeroutput>--vex-iropt-precise-memory-exns=yes</computeroutput>. |
| </para> |
| |
| <para>If your program dies as a result of a fatal core-dumping signal, |
| Valgrind will generate its own core file |
| (<computeroutput>vgcore.NNNNN</computeroutput>) containing your program's |
| state. You may use this core file for post-mortem debugging with gdb or |
| similar. (Note: it will not generate a core if your core dump size limit is |
| 0.) At the time of writing the core dumps do not include all the floating |
| point register information.</para> |
| |
| <para>In the unlikely event that Valgrind itself crashes, the operating system |
| will create a core dump in the usual way.</para> |
| |
| </sect1> |
| |
| |
| |
| |
| |
| |
| |
| |
| <sect1 id="manual-core.install" xreflabel="Building and Installing"> |
| <title>Building and Installing Valgrind</title> |
| |
| <para>We use the standard Unix |
| <computeroutput>./configure</computeroutput>, |
| <computeroutput>make</computeroutput>, <computeroutput>make |
| install</computeroutput> mechanism, and we have attempted to |
| ensure that it works on machines with kernel 2.4 or 2.6 and glibc |
| 2.2.X to 2.5.X. Once you have completed |
| <computeroutput>make install</computeroutput> you may then want |
| to run the regression tests |
| with <computeroutput>make regtest</computeroutput>. |
| </para> |
| |
| <para>There are five options (in addition to the usual |
| <option>--prefix=</option> which affect how Valgrind is built: |
| <itemizedlist> |
| |
| <listitem> |
| <para><option>--enable-inner</option></para> |
| <para>This builds Valgrind with some special magic hacks which make |
| it possible to run it on a standard build of Valgrind (what the |
| developers call "self-hosting"). Ordinarily you should not use |
| this flag as various kinds of safety checks are disabled. |
| </para> |
| </listitem> |
| |
| <listitem> |
| <para><option>--enable-tls</option></para> |
| <para>TLS (Thread Local Storage) is a relatively new mechanism which |
| requires compiler, linker and kernel support. Valgrind tries to |
| automatically test if TLS is supported and if so enables this option. |
| Sometimes it cannot test for TLS, so this option allows you to |
| override the automatic test.</para> |
| </listitem> |
| |
| <listitem> |
| <para><option>--with-vex=</option></para> |
| <para>Specifies the path to the underlying VEX dynamic-translation |
| library. By default this is taken to be in the VEX directory off |
| the root of the source tree. |
| </para> |
| </listitem> |
| |
| <listitem> |
| <para><option>--enable-only64bit</option></para> |
| <para><option>--enable-only32bit</option></para> |
| <para>On 64-bit |
| platforms (amd64-linux, ppc64-linux), Valgrind is by default built |
| in such a way that both 32-bit and 64-bit executables can be run. |
| Sometimes this cleverness is a problem for a variety of reasons. |
| These two flags allow for single-target builds in this situation. |
| If you issue both, the configure script will complain. Note they |
| are ignored on 32-bit-only platforms (x86-linux, ppc32-linux). |
| </para> |
| </listitem> |
| |
| </itemizedlist> |
| </para> |
| |
| <para>The <computeroutput>configure</computeroutput> script tests |
| the version of the X server currently indicated by the current |
| <computeroutput>$DISPLAY</computeroutput>. This is a known bug. |
| The intention was to detect the version of the current X |
| client libraries, so that correct suppressions could be selected |
| for them, but instead the test checks the server version. This |
| is just plain wrong.</para> |
| |
| <para>If you are building a binary package of Valgrind for |
| distribution, please read <literal>README_PACKAGERS</literal> |
| <xref linkend="dist.readme-packagers"/>. It contains some |
| important information.</para> |
| |
| <para>Apart from that, there's not much excitement here. Let us |
| know if you have build problems.</para> |
| |
| </sect1> |
| |
| |
| |
| <sect1 id="manual-core.problems" xreflabel="If You Have Problems"> |
| <title>If You Have Problems</title> |
| |
| <para>Contact us at <ulink url="&vg-url;">&vg-url;</ulink>.</para> |
| |
| <para>See <xref linkend="manual-core.limits"/> for the known |
| limitations of Valgrind, and for a list of programs which are |
| known not to work on it.</para> |
| |
| <para>All parts of the system make heavy use of assertions and |
| internal self-checks. They are permanently enabled, and we have no |
| plans to disable them. If one of them breaks, please mail us!</para> |
| |
| <para>If you get an assertion failure |
| in <filename>m_mallocfree.c</filename>, this may have happened because |
| your program wrote off the end of a malloc'd block, or before its |
| beginning. Valgrind hopefully will have emitted a proper message to that |
| effect before dying in this way. This is a known problem which |
| we should fix.</para> |
| |
| <para>Read the <xref linkend="FAQ"/> for more advice about common problems, |
| crashes, etc.</para> |
| |
| </sect1> |
| |
| |
| |
| <sect1 id="manual-core.limits" xreflabel="Limitations"> |
| <title>Limitations</title> |
| |
| <para>The following list of limitations seems long. However, most |
| programs actually work fine.</para> |
| |
| <para>Valgrind will run Linux ELF binaries, on a kernel 2.4.X or 2.6.X |
| system, on the x86, amd64, ppc32 and ppc64 architectures, subject to the |
| following constraints:</para> |
| |
| <itemizedlist> |
| <listitem> |
| <para>On x86 and amd64, there is no support for 3DNow! instructions. |
| If the translator encounters these, Valgrind will generate a SIGILL |
| when the instruction is executed. Apart from that, on x86 and amd64, |
| essentially all instructions are supported, up to and including SSE3. |
| </para> |
| |
| <para>On ppc32 and ppc64, almost all integer, floating point and Altivec |
| instructions are supported. Specifically: integer and FP insns that are |
| mandatory for PowerPC, the "General-purpose optional" group (fsqrt, fsqrts, |
| stfiwx), the "Graphics optional" group (fre, fres, frsqrte, frsqrtes), and |
| the Altivec (also known as VMX) SIMD instruction set, are supported.</para> |
| </listitem> |
| |
| <listitem> |
| <para>Atomic instruction sequences are not properly supported, in the |
| sense that their atomicity is not preserved. This will affect any |
| use of synchronization via memory shared between processes. They |
| will appear to work, but fail sporadically.</para> |
| </listitem> |
| |
| <listitem> |
| <para>If your program does its own memory management, rather than |
| using malloc/new/free/delete, it should still work, but Memcheck's |
| error checking won't be so effective. If you describe your program's |
| memory management scheme using "client requests" |
| (see <xref linkend="manual-core-adv.clientreq"/>), Memcheck can do |
| better. Nevertheless, using malloc/new and free/delete is still the |
| best approach.</para> |
| </listitem> |
| |
| <listitem> |
| <para>Valgrind's signal simulation is not as robust as it could be. |
| Basic POSIX-compliant sigaction and sigprocmask functionality is |
| supplied, but it's conceivable that things could go badly awry if you |
| do weird things with signals. Workaround: don't. Programs that do |
| non-POSIX signal tricks are in any case inherently unportable, so |
| should be avoided if possible.</para> |
| </listitem> |
| |
| <listitem> |
| <para>Machine instructions, and system calls, have been implemented |
| on demand. So it's possible, although unlikely, that a program will |
| fall over with a message to that effect. If this happens, please |
| report all the details printed out, so we can try and implement the |
| missing feature.</para> |
| </listitem> |
| |
| <listitem> |
| <para>Memory consumption of your program is majorly increased whilst |
| running under Valgrind. This is due to the large amount of |
| administrative information maintained behind the scenes. Another |
| cause is that Valgrind dynamically translates the original |
| executable. Translated, instrumented code is 12-18 times larger than |
| the original so you can easily end up with 50+ MB of translations |
| when running (eg) a web browser.</para> |
| </listitem> |
| |
| <listitem> |
| <para>Valgrind can handle dynamically-generated code just fine. If |
| you regenerate code over the top of old code (ie. at the same memory |
| addresses), if the code is on the stack Valgrind will realise the |
| code has changed, and work correctly. This is necessary to handle |
| the trampolines GCC uses to implemented nested functions. If you |
| regenerate code somewhere other than the stack, you will need to use |
| the <option>--smc-check=all</option> flag, and Valgrind will run more |
| slowly than normal.</para> |
| </listitem> |
| |
| <listitem> |
| <para>As of version 3.0.0, Valgrind has the following limitations |
| in its implementation of x86/AMD64 floating point relative to |
| IEEE754.</para> |
| |
| <para>Precision: There is no support for 80 bit arithmetic. |
| Internally, Valgrind represents all such "long double" numbers in 64 |
| bits, and so there may be some differences in results. Whether or |
| not this is critical remains to be seen. Note, the x86/amd64 |
| fldt/fstpt instructions (read/write 80-bit numbers) are correctly |
| simulated, using conversions to/from 64 bits, so that in-memory |
| images of 80-bit numbers look correct if anyone wants to see.</para> |
| |
| <para>The impression observed from many FP regression tests is that |
| the accuracy differences aren't significant. Generally speaking, if |
| a program relies on 80-bit precision, there may be difficulties |
| porting it to non x86/amd64 platforms which only support 64-bit FP |
| precision. Even on x86/amd64, the program may get different results |
| depending on whether it is compiled to use SSE2 instructions (64-bits |
| only), or x87 instructions (80-bit). The net effect is to make FP |
| programs behave as if they had been run on a machine with 64-bit IEEE |
| floats, for example PowerPC. On amd64 FP arithmetic is done by |
| default on SSE2, so amd64 looks more like PowerPC than x86 from an FP |
| perspective, and there are far fewer noticeable accuracy differences |
| than with x86.</para> |
| |
| <para>Rounding: Valgrind does observe the 4 IEEE-mandated rounding |
| modes (to nearest, to +infinity, to -infinity, to zero) for the |
| following conversions: float to integer, integer to float where |
| there is a possibility of loss of precision, and float-to-float |
| rounding. For all other FP operations, only the IEEE default mode |
| (round to nearest) is supported.</para> |
| |
| <para>Numeric exceptions in FP code: IEEE754 defines five types of |
| numeric exception that can happen: invalid operation (sqrt of |
| negative number, etc), division by zero, overflow, underflow, |
| inexact (loss of precision).</para> |
| |
| <para>For each exception, two courses of action are defined by IEEE754: |
| either (1) a user-defined exception handler may be called, or (2) a |
| default action is defined, which "fixes things up" and allows the |
| computation to proceed without throwing an exception.</para> |
| |
| <para>Currently Valgrind only supports the default fixup actions. |
| Again, feedback on the importance of exception support would be |
| appreciated.</para> |
| |
| <para>When Valgrind detects that the program is trying to exceed any |
| of these limitations (setting exception handlers, rounding mode, or |
| precision control), it can print a message giving a traceback of |
| where this has happened, and continue execution. This behaviour used |
| to be the default, but the messages are annoying and so showing them |
| is now disabled by default. Use <option>--show-emwarns=yes</option> to see |
| them.</para> |
| |
| <para>The above limitations define precisely the IEEE754 'default' |
| behaviour: default fixup on all exceptions, round-to-nearest |
| operations, and 64-bit precision.</para> |
| </listitem> |
| |
| <listitem> |
| <para>As of version 3.0.0, Valgrind has the following limitations in |
| its implementation of x86/AMD64 SSE2 FP arithmetic, relative to |
| IEEE754.</para> |
| |
| <para>Essentially the same: no exceptions, and limited observance of |
| rounding mode. Also, SSE2 has control bits which make it treat |
| denormalised numbers as zero (DAZ) and a related action, flush |
| denormals to zero (FTZ). Both of these cause SSE2 arithmetic to be |
| less accurate than IEEE requires. Valgrind detects, ignores, and can |
| warn about, attempts to enable either mode.</para> |
| </listitem> |
| |
| <listitem> |
| <para>As of version 3.2.0, Valgrind has the following limitations |
| in its implementation of PPC32 and PPC64 floating point |
| arithmetic, relative to IEEE754.</para> |
| |
| <para>Scalar (non-Altivec): Valgrind provides a bit-exact emulation of |
| all floating point instructions, except for "fre" and "fres", which are |
| done more precisely than required by the PowerPC architecture specification. |
| All floating point operations observe the current rounding mode. |
| </para> |
| |
| <para>However, fpscr[FPRF] is not set after each operation. That could |
| be done but would give measurable performance overheads, and so far |
| no need for it has been found.</para> |
| |
| <para>As on x86/AMD64, IEEE754 exceptions are not supported: all floating |
| point exceptions are handled using the default IEEE fixup actions. |
| Valgrind detects, ignores, and can warn about, attempts to unmask |
| the 5 IEEE FP exception kinds by writing to the floating-point status |
| and control register (fpscr). |
| </para> |
| |
| <para>Vector (Altivec, VMX): essentially as with x86/AMD64 SSE/SSE2: |
| no exceptions, and limited observance of rounding mode. |
| For Altivec, FP arithmetic |
| is done in IEEE/Java mode, which is more accurate than the Linux default |
| setting. "More accurate" means that denormals are handled properly, |
| rather than simply being flushed to zero.</para> |
| </listitem> |
| </itemizedlist> |
| |
| <para>Programs which are known not to work are:</para> |
| <itemizedlist> |
| <listitem> |
| <para>emacs starts up but immediately concludes it is out of |
| memory and aborts. It may be that Memcheck does not provide |
| a good enough emulation of the |
| <computeroutput>mallinfo</computeroutput> function. |
| Emacs works fine if you build it to use |
| the standard malloc/free routines.</para> |
| </listitem> |
| </itemizedlist> |
| |
| </sect1> |
| |
| |
| <sect1 id="manual-core.example" xreflabel="An Example Run"> |
| <title>An Example Run</title> |
| |
| <para>This is the log for a run of a small program using Memcheck. |
| The program is in fact correct, and the reported error is as the |
| result of a potentially serious code generation bug in GNU g++ |
| (snapshot 20010527).</para> |
| |
| <programlisting><![CDATA[ |
| sewardj@phoenix:~/newmat10$ ~/Valgrind-6/valgrind -v ./bogon |
| ==25832== Valgrind 0.10, a memory error detector for x86 RedHat 7.1. |
| ==25832== Copyright (C) 2000-2001, and GNU GPL'd, by Julian Seward. |
| ==25832== Startup, with flags: |
| ==25832== --suppressions=/home/sewardj/Valgrind/redhat71.supp |
| ==25832== reading syms from /lib/ld-linux.so.2 |
| ==25832== reading syms from /lib/libc.so.6 |
| ==25832== reading syms from /mnt/pima/jrs/Inst/lib/libgcc_s.so.0 |
| ==25832== reading syms from /lib/libm.so.6 |
| ==25832== reading syms from /mnt/pima/jrs/Inst/lib/libstdc++.so.3 |
| ==25832== reading syms from /home/sewardj/Valgrind/valgrind.so |
| ==25832== reading syms from /proc/self/exe |
| ==25832== |
| ==25832== Invalid read of size 4 |
| ==25832== at 0x8048724: BandMatrix::ReSize(int,int,int) (bogon.cpp:45) |
| ==25832== by 0x80487AF: main (bogon.cpp:66) |
| ==25832== Address 0xBFFFF74C is not stack'd, malloc'd or free'd |
| ==25832== |
| ==25832== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0) |
| ==25832== malloc/free: in use at exit: 0 bytes in 0 blocks. |
| ==25832== malloc/free: 0 allocs, 0 frees, 0 bytes allocated. |
| ==25832== For a detailed leak analysis, rerun with: --leak-check=yes |
| ]]></programlisting> |
| |
| <para>The GCC folks fixed this about a week before gcc-3.0 |
| shipped.</para> |
| |
| </sect1> |
| |
| |
| <sect1 id="manual-core.warnings" xreflabel="Warning Messages"> |
| <title>Warning Messages You Might See</title> |
| |
| <para>Most of these only appear if you run in verbose mode |
| (enabled by <computeroutput>-v</computeroutput>):</para> |
| |
| <itemizedlist> |
| |
| <listitem> |
| <para><computeroutput>More than 100 errors detected. Subsequent |
| errors will still be recorded, but in less detail than |
| before.</computeroutput></para> |
| |
| <para>After 100 different errors have been shown, Valgrind becomes |
| more conservative about collecting them. It then requires only the |
| program counters in the top two stack frames to match when deciding |
| whether or not two errors are really the same one. Prior to this |
| point, the PCs in the top four frames are required to match. This |
| hack has the effect of slowing down the appearance of new errors |
| after the first 100. The 100 constant can be changed by recompiling |
| Valgrind.</para> |
| </listitem> |
| |
| <listitem> |
| <para><computeroutput>More than 1000 errors detected. I'm not |
| reporting any more. Final error counts may be inaccurate. Go fix |
| your program!</computeroutput></para> |
| |
| <para>After 1000 different errors have been detected, Valgrind |
| ignores any more. It seems unlikely that collecting even more |
| different ones would be of practical help to anybody, and it avoids |
| the danger that Valgrind spends more and more of its time comparing |
| new errors against an ever-growing collection. As above, the 1000 |
| number is a compile-time constant.</para> |
| </listitem> |
| |
| <listitem> |
| <para><computeroutput>Warning: client switching stacks?</computeroutput></para> |
| |
| <para>Valgrind spotted such a large change in the stack pointer |
| that it guesses the client is switching to |
| a different stack. At this point it makes a kludgey guess where the |
| base of the new stack is, and sets memory permissions accordingly. |
| You may get many bogus error messages following this, if Valgrind |
| guesses wrong. At the moment "large change" is defined as a change |
| of more that 2000000 in the value of the |
| stack pointer register.</para> |
| </listitem> |
| |
| <listitem> |
| <para><computeroutput>Warning: client attempted to close Valgrind's |
| logfile fd <number></computeroutput></para> |
| |
| <para>Valgrind doesn't allow the client to close the logfile, |
| because you'd never see any diagnostic information after that point. |
| If you see this message, you may want to use the |
| <option>--log-fd=<number></option> option to specify a |
| different logfile file-descriptor number.</para> |
| </listitem> |
| |
| <listitem> |
| <para><computeroutput>Warning: noted but unhandled ioctl |
| <number></computeroutput></para> |
| |
| <para>Valgrind observed a call to one of the vast family of |
| <computeroutput>ioctl</computeroutput> system calls, but did not |
| modify its memory status info (because nobody has yet written a |
| suitable wrapper). The call will still have gone through, but you may get |
| spurious errors after this as a result of the non-update of the |
| memory info.</para> |
| </listitem> |
| |
| <listitem> |
| <para><computeroutput>Warning: set address range perms: large range |
| <number></computeroutput></para> |
| |
| <para>Diagnostic message, mostly for benefit of the Valgrind |
| developers, to do with memory permissions.</para> |
| </listitem> |
| |
| </itemizedlist> |
| |
| </sect1> |
| |
| |
| |
| |
| |
| |
| </chapter> |