mstorsjo wrote: > Maybe this is a hidden bug, but I haven't investigated it too deeply, > @mstorsjo may know better.
Sorry, no clue offhand here. > If you build MinGW LTO libunwind without `-fno-exceptions` or with > -`fexceptions`, libunwind references `__gcc_personality_seh0`, which results > in undefined symbols. Perhaps this is a symbol which we need to implicitly mark as needed in the linker? Because before the LTO, I think it only sees a definition of this symbol, but nothing referencing it, so the LTO logic thinks it doesn't need to retain/expose this symbol - while after the LTO, the generated code does add new references to it. I don't find any precedence for doing this for LTO so far, but we have a couple cases of doing something similar for the regular GC in LLD. > cmake normally adds `-fno-exceptionson`, but not on the first build, because > the toolchain is incomplete which causes cmake to think that the compiler > doesn't support `-fno-exceptions`, which is how I found out about the problem. It does add `-fno-exceptions` even on the first bootstrap build for me. See e.g. https://github.com/mstorsjo/llvm-mingw/actions/runs/12662020869/job/35286224252#step:3:23134: ``` -- The C compiler identification is Clang 20.0.0 -- The CXX compiler identification is Clang 20.0.0 -- The ASM compiler identification is Clang with GNU-like command-line -- Found assembler: /home/runner/work/llvm-mingw/llvm-mingw/install/llvm-mingw/bin/i686-w64-mingw32-clang -- Detecting C compiler ABI info -- Detecting C compiler ABI info - failed -- Detecting C compile features -- Detecting C compile features - done -- Detecting CXX compiler ABI info -- Detecting CXX compiler ABI info - failed -- Detecting CXX compile features -- Detecting CXX compile features - done [...] -- Performing Test CXX_SUPPORTS_FUNWIND_TABLES_FLAG -- Performing Test CXX_SUPPORTS_FUNWIND_TABLES_FLAG - Success -- Performing Test CXX_SUPPORTS_FNO_EXCEPTIONS_FLAG -- Performing Test CXX_SUPPORTS_FNO_EXCEPTIONS_FLAG - Success ``` https://github.com/llvm/llvm-project/pull/121819 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
