Hi! As mentioned in the PR, since the switch to DWARF5 by default instead of DWARF4, gcc fails to build when configured against recent binutils.
The problem is that cxx11-ios_failure* is built in separate steps, -S compilation (with -g -O2) followed by some sed and followed by -c -g -O2 -g0 assembly. When gcc is configured against recent binutils and DWARF5 is the default, we emit .file 0 "..." directive on which the assembler then fails (unless --gdwarf-5 is passed to it, but we don't want that generally because on the other side older assemblers don't like -g* passed to it when invoked on *.s file with compiler generated debug info. I hope the bug will be fixed soon on the binutils side, but it would be nice to have a workaround. The following patch is one of the possibilities, another one is to do that but add configure check for whether it is needed, essentially echo 'int main () { return 0; }' > conftest.c ${CXX} ${CXXFLAGS} -g -O2 -S conftest.c -o conftest.s ${CXX} ${CXXFLAGS} -g -O2 -g0 -c conftest.s -o conftest.o and if the last command fails, we need that -gno-as-loc-support. Or yet another option would be I think do a different check, whether ${CXX} ${CXXFLAGS} -g -O2 -S conftest.c -o conftest.s ${CXX} ${CXXFLAGS} -g -O2 -c conftest.s -o conftest.o works and if yes, don't add the -g0 to cxx11-ios_failure*.s assembly. I've successfully bootstrapped/regtested this version on x86_64-linux and i686-linux. 2021-01-18 Jakub Jelinek <ja...@redhat.com> PR debug/98708 * src/c++11/Makefile.am (cxx11-ios_failure-lt.s, cxx11-ios_failure.s): Compile with -gno-as-loc-support. * src/c++11/Makefile.in: Regenerated. --- libstdc++-v3/src/c++11/Makefile.am.jj 2021-01-04 10:26:02.067970728 +0100 +++ libstdc++-v3/src/c++11/Makefile.am 2021-01-17 17:20:58.580262364 +0100 @@ -141,12 +141,12 @@ if ENABLE_DUAL_ABI rewrite_ios_failure_typeinfo = sed -e '/^_*_ZTISt13__ios_failure:/,/_ZTVN10__cxxabiv120__si_class_type_infoE/s/_ZTVN10__cxxabiv120__si_class_type_infoE/_ZTVSt19__iosfail_type_info/' cxx11-ios_failure-lt.s: cxx11-ios_failure.cc - $(LTCXXCOMPILE) -S $< -o tmp-cxx11-ios_failure-lt.s + $(LTCXXCOMPILE) -gno-as-loc-support -S $< -o tmp-cxx11-ios_failure-lt.s -test -f tmp-cxx11-ios_failure-lt.o && mv -f tmp-cxx11-ios_failure-lt.o tmp-cxx11-ios_failure-lt.s $(rewrite_ios_failure_typeinfo) tmp-$@ > $@ -rm -f tmp-$@ cxx11-ios_failure.s: cxx11-ios_failure.cc - $(CXXCOMPILE) -S $< -o tmp-$@ + $(CXXCOMPILE) -gno-as-loc-support -S $< -o tmp-$@ $(rewrite_ios_failure_typeinfo) tmp-$@ > $@ -rm -f tmp-$@ --- libstdc++-v3/src/c++11/Makefile.in.jj 2020-12-17 02:29:28.734557483 +0100 +++ libstdc++-v3/src/c++11/Makefile.in 2021-01-17 17:21:27.510931383 +0100 @@ -852,12 +852,12 @@ limits.o: limits.cc $(CXXCOMPILE) -fchar8_t -c $< @ENABLE_DUAL_ABI_TRUE@cxx11-ios_failure-lt.s: cxx11-ios_failure.cc -@ENABLE_DUAL_ABI_TRUE@ $(LTCXXCOMPILE) -S $< -o tmp-cxx11-ios_failure-lt.s +@ENABLE_DUAL_ABI_TRUE@ $(LTCXXCOMPILE) -gno-as-loc-support -S $< -o tmp-cxx11-ios_failure-lt.s @ENABLE_DUAL_ABI_TRUE@ -test -f tmp-cxx11-ios_failure-lt.o && mv -f tmp-cxx11-ios_failure-lt.o tmp-cxx11-ios_failure-lt.s @ENABLE_DUAL_ABI_TRUE@ $(rewrite_ios_failure_typeinfo) tmp-$@ > $@ @ENABLE_DUAL_ABI_TRUE@ -rm -f tmp-$@ @ENABLE_DUAL_ABI_TRUE@cxx11-ios_failure.s: cxx11-ios_failure.cc -@ENABLE_DUAL_ABI_TRUE@ $(CXXCOMPILE) -S $< -o tmp-$@ +@ENABLE_DUAL_ABI_TRUE@ $(CXXCOMPILE) -gno-as-loc-support -S $< -o tmp-$@ @ENABLE_DUAL_ABI_TRUE@ $(rewrite_ios_failure_typeinfo) tmp-$@ > $@ @ENABLE_DUAL_ABI_TRUE@ -rm -f tmp-$@ Jakub