Bug#996798: llvm-toolchain-12: FTBFS on mipsel|powerpc since 1:12.0.1-10: undefined reference to `_Unwind_Resume' etc.

[Simon McVittie]

Source: llvm-toolchain-12
Version: 1:12.0.1-10
Severity: serious
Tags: ftbfs
Justification: fails to build from source (but built successfully in the past)

The restructuring in 1:12.0.1-10 seems to have caused a build regression
on mipsel, which I'm reporting as separate from #996796 because it
doesn't affect i386:

> [1050/1054] : && /<<PKGBUILDDIR>>/build-llvm/./bin/clang++ --target=mipsel-unknown-linux-gnu -fPIC -g -O2 -fdebug-prefix-map=/<<PKGBUILDDIR>>=. -fstack-protector-strong -Wformat -Werror=format-security -fPIC -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wno-comment -Wstring-conversion -fdiagnostics-color -ffunction-sections -fdata-sections  -O3 -DNDEBUG  -Wl,-z,relro -Wl,-z,defs -Wl,-z,nodelete  -nodefaultlibs -shared -Wl,-soname,libc++abi.so.1 -o /<<PKGBUILDDIR>>/build-llvm/lib/libc++abi.so.1.0 libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_aux_runtime.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_default_handlers.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_demangle.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_exception_storage.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_guard.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_handlers.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_vector.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_virtual.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/stdlib_exception.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/stdlib_stdexcept.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/stdlib_typeinfo.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/abort_message.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/fallback_malloc.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/private_typeinfo.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/stdlib_new_delete.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_exception.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_personality.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_thread_atexit.cpp.o  -lpthread  -lc && :
> FAILED: /<<PKGBUILDDIR>>/build-llvm/lib/libc++abi.so.1.0 
> : && /<<PKGBUILDDIR>>/build-llvm/./bin/clang++ --target=mipsel-unknown-linux-gnu -fPIC -g -O2 -fdebug-prefix-map=/<<PKGBUILDDIR>>=. -fstack-protector-strong -Wformat -Werror=format-security -fPIC -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wno-comment -Wstring-conversion -fdiagnostics-color -ffunction-sections -fdata-sections  -O3 -DNDEBUG  -Wl,-z,relro -Wl,-z,defs -Wl,-z,nodelete  -nodefaultlibs -shared -Wl,-soname,libc++abi.so.1 -o /<<PKGBUILDDIR>>/build-llvm/lib/libc++abi.so.1.0 libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_aux_runtime.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_default_handlers.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_demangle.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_exception_storage.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_guard.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_handlers.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_vector.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_virtual.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/stdlib_exception.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/stdlib_stdexcept.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/stdlib_typeinfo.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/abort_message.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/fallback_malloc.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/private_typeinfo.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/stdlib_new_delete.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_exception.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_personality.cpp.o libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_thread_atexit.cpp.o  -lpthread  -lc && :
> /usr/bin/ld: libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_guard.cpp.o: in function `~LockGuard':
> ./build-llvm/runtimes/runtimes-bins/./libcxxabi/src/cxa_guard_impl.h:(.text.unlikely.__cxa_guard_acquire+0x1cc): undefined reference to `_Unwind_Resume'
> /usr/bin/ld: ./build-llvm/runtimes/runtimes-bins/./libcxxabi/src/cxa_guard_impl.h:(.text.unlikely.__cxa_guard_acquire+0x1d4): undefined reference to `_Unwind_Resume'
> /usr/bin/ld: libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_demangle.cpp.o: in function `~AbstractManglingParser':
> ./build-llvm/runtimes/runtimes-bins/./libcxxabi/src/demangle/ItaniumDemangle.h:(.text.__cxa_demangle+0x94c): undefined reference to `_Unwind_Resume'
> /usr/bin/ld: ./build-llvm/runtimes/runtimes-bins/./libcxxabi/src/demangle/ItaniumDemangle.h:(.text.__cxa_demangle+0x954): undefined reference to `_Unwind_Resume'
> /usr/bin/ld: libcxxabi/src/CMakeFiles/cxxabi_shared.dir/cxa_demangle.cpp.o: in function `~PODSmallVector':
> ./build-llvm/runtimes/runtimes-bins/./libcxxabi/src/demangle/ItaniumDemangle.h:(.text.__cxa_demangle+0xa04): undefined reference to `_Unwind_Resume'
[and lots more _Unwind_Foo references]

I assume this is resulting from -nodefaultlibs not causing libunwind
to be linked in where necessary?

Among non-release ports, powerpc also has this. mipsel and powerpc also
have #996796.

    smcv