On i686-pc-linux-gnu, seven libstdc++-v3 symbols are missing when configuring with --enable-build-with-cxx. For x86_64-unknown-linux-gnu, it's 53 vs. 46 missing symbols, i.e. again seven more missing symbols for --enable-build-with-cxx.
Take for example: __gnu_parallel::_Settings::get() In the ordinary compilation, this symbol is defined in parallel_settings.o; that object file is missing for --enable-build-with-cxx. compilation of parallel_settings.cc depends on ENABLE_PARALLEL, set by configure. Inspection of the src/Makefile files shows that ENABLE_PARALLEL was not set for --enable-build-with-cxx . The building of parallel_list.o also depends on ENABLE_PARALLEL; parallel_list and parallel_settings together account for the seven missing symbols. The normal bootstrap log file shows: line 11064/21065: checking for parallel mode support... yes The --enable-build-with-cxx bootstrap log file shows: line 4234/23482: configure: /user/inria/fsf/bld-gcc-cxx12/i686-pc-linux-gnu/libstdc++-v3/../libgo mp/omp.h not found checking for parallel mode support... no line 8212/23482: configure: /user/inria/fsf/bld-gcc-cxx12/i686-pc-linux-gnu/libstdc++-v3/../libgo mp/omp.h not found checking for parallel mode support... no line 12192/23482: configure: /user/inria/fsf/bld-gcc-cxx12/i686-pc-linux-gnu/libstdc++-v3/../libgomp/omp.h not found checking for parallel mode support... no The normal bootstrap log shows: line 9732/21065: Configuring in i686-pc-linux-gnu/libgomp The --enable-build-with-cxx bootstrap log file shows: line 12983/23482: Configuring in i686-pc-linux-gnu/libgomp I.e. the problem is that libgomp is not built before the final libstdc++-v3 is configured. -- Summary: --enable-build-with-cxx libstdc++-v3 is incomplete Product: gcc Version: 4.5.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: other AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: amylaar at gcc dot gnu dot org http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42813