--- HACKING | 93 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 87 insertions(+), 6 deletions(-) diff --git a/HACKING b/HACKING index c7df3f3..e1e0b9b 100644 --- a/HACKING +++ b/HACKING @@ -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. - - - -(7) Update tests and/or documentation, particularly if you are adding a new +various tests under gdb or Valgrind. + + + +(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. -- 1.7.11.7 -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list