As of r163210 (http://gcc.gnu.org/viewcvs?view=revision&revision=163210) libstdc++ has two new macros: _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER and a short documentation for them in include/bits/c++config
I propose to add a more detailed documentation (though I don't know the exact place where to add it). The proposed text follows. See also the discussion at http://old.nabble.com/Re:-libstdc%2B%2B-and-race-detectors-to29116684.html Support for race detectors. All synchronization primitives used in the library internals should be understood by race detectors so that the race detectors do not produce false reports. We use two annotations (macros) to explain low-level synchronization to race detectors: - _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE() and - _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(). By default, these two macros are defined empty -- anyone who wants to use a race detector will need to redefine these macros to call appropriate race detector API. Since these macros are empty by default, redefining them in the user code will affect only the inline template code, i.e. shared_ptr. In order to redefine the macros in basic_string one will need to disable extern templates (by defining _GLIBCXX_EXTERN_TEMPLATE=-1) or rebuild the .so. The rest of the cases will require to rebuild the .so: - ios_base::Init::~Init - locale::_Impl and locale::facet The approach described above works at least with the following race detection tools: - DRD, http://valgrind.org/docs/manual/drd-manual.html - Helgrind, http://valgrind.org/docs/manual/hg-manual.html - Intel Parallel Inspector, http://software.intel.com/en-us/intel-parallel-inspector - ThreadSanitizer, http://code.google.com/p/data-race-test With DRD, Helgrind and ThreadSanitizer you will need to define the macros like this: #define _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(a) ANNOTATE_HAPPENS_BEFORE(a); #define _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(a) ANNOTATE_HAPPENS_AFTER(a); For Intel Parallel Inspector: #define _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE(a) itt_notify_sync_releasing(a); #define _GLIBCXX_SYNCHRONIZATION_HAPPENS_AFTER(a) itt_notify_sync_acquired(a); Refer to the documentation of a particular tool for the details. -- Summary: Need to document _GLIBCXX_SYNCHRONIZATION_HAPPENS_BEFORE Product: gcc Version: 4.6.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: libstdc++ AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: konstantin dot s dot serebryany at gmail dot com http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45276
