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HACKING: Sync with docs/hacking.html.in

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John Ferlan 2013-02-05 18:20:58 -05:00
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@ -103,7 +103,11 @@ and run the tests:
make syntax-check
make -C tests valgrind
The latter test checks for memory leaks.
Valgrind
http://valgrind.org/is a test that checks for memory management issues, such as leaks or use of
uninitialized variables.
If you encounter any failing tests, the VIR_TEST_DEBUG environment variable
may provide extra information to debug the failures. Larger values of
@ -118,11 +122,88 @@ Also, individual tests can be run from inside the "tests/" directory, like:
There is also a "./run" script at the top level, to make it easier to run
programs that have not yet been installed, as well as to wrap invocations of
various tests under gdb or valgrind.
various tests under gdb or Valgrind.
(7) Update tests and/or documentation, particularly if you are adding a new
(7) The Valgrind test should produce similar output to "make check". If the output
has traces within libvirt API's, then investigation is required in order to
determine the cause of the issue. Output such as the following indicates some
sort of leak:
==5414== 4 bytes in 1 blocks are definitely lost in loss record 3 of 89
==5414== at 0x4A0881C: malloc (vg_replace_malloc.c:270)
==5414== by 0x34DE0AAB85: xmlStrndup (in /usr/lib64/libxml2.so.2.7.8)
==5414== by 0x4CC97A6: virDomainVideoDefParseXML (domain_conf.c:7410)
==5414== by 0x4CD581D: virDomainDefParseXML (domain_conf.c:10188)
==5414== by 0x4CD8C73: virDomainDefParseNode (domain_conf.c:10640)
==5414== by 0x4CD8DDB: virDomainDefParse (domain_conf.c:10590)
==5414== by 0x41CB1D: testCompareXMLToArgvHelper (qemuxml2argvtest.c:100)
==5414== by 0x41E20F: virtTestRun (testutils.c:161)
==5414== by 0x41C7CB: mymain (qemuxml2argvtest.c:866)
==5414== by 0x41E84A: virtTestMain (testutils.c:723)
==5414== by 0x34D9021734: (below main) (in /usr/lib64/libc-2.15.so)
In this example, the "virDomainDefParseXML()" had an error path where the
"virDomainVideoDefPtr video" pointer was not properly disposed. By simply
adding a "virDomainVideoDefFree(video);" in the error path, the issue was
resolved.
Another common mistake is calling a printing function, such as "VIR_DEBUG()"
without initializing a variable to be printed. The following example involved
a call which could return an error, but not set variables passed by reference
to the call. The solution was to initialize the variables prior to the call.
==4749== Use of uninitialised value of size 8
==4749== at 0x34D904650B: _itoa_word (in /usr/lib64/libc-2.15.so)
==4749== by 0x34D9049118: vfprintf (in /usr/lib64/libc-2.15.so)
==4749== by 0x34D9108F60: __vasprintf_chk (in /usr/lib64/libc-2.15.so)
==4749== by 0x4CAEEF7: virVasprintf (stdio2.h:199)
==4749== by 0x4C8A55E: virLogVMessage (virlog.c:814)
==4749== by 0x4C8AA96: virLogMessage (virlog.c:751)
==4749== by 0x4DA0056: virNetTLSContextCheckCertKeyUsage (virnettlscontext.c:225)
==4749== by 0x4DA06DB: virNetTLSContextCheckCert (virnettlscontext.c:439)
==4749== by 0x4DA1620: virNetTLSContextNew (virnettlscontext.c:562)
==4749== by 0x4DA26FC: virNetTLSContextNewServer (virnettlscontext.c:927)
==4749== by 0x409C39: testTLSContextInit (virnettlscontexttest.c:467)
==4749== by 0x40AB8F: virtTestRun (testutils.c:161)
Valgrind will also find some false positives or code paths which cannot be
resolved by making changes to the libvirt code. For these paths, it is
possible to add a filter to avoid the errors. For example:
==4643== 7 bytes in 1 blocks are possibly lost in loss record 4 of 20
==4643== at 0x4A0881C: malloc (vg_replace_malloc.c:270)
==4643== by 0x34D90853F1: strdup (in /usr/lib64/libc-2.15.so)
==4643== by 0x34EEC2C08A: ??? (in /usr/lib64/libnl.so.1.1)
==4643== by 0x34EEC15B81: ??? (in /usr/lib64/libnl.so.1.1)
==4643== by 0x34D8C0EE15: call_init.part.0 (in /usr/lib64/ld-2.15.so)
==4643== by 0x34D8C0EECF: _dl_init (in /usr/lib64/ld-2.15.so)
==4643== by 0x34D8C01569: ??? (in /usr/lib64/ld-2.15.so)
In this instance, it is acceptible to modify the "tests/.valgrind.supp" file
in order to add a suppression filter. The filter should be unique enough to
not suppress real leaks, but it should be generic enough to cover multiple
code paths. The format of the entry can be found in the documentation found at
the
Valgrind home page.
http://valgrind.org/The following trace was added to "tests/.valgrind.supp" in order to suppress
the warning:
{
dlInitMemoryLeak1
Memcheck:Leak
fun:?alloc
...
fun:call_init.part.0
fun:_dl_init
...
obj:*/lib*/ld-2.*so*
}
(8) Update tests and/or documentation, particularly if you are adding a new
feature or changing the output of a program.