Hi,

Bumping this thread. Is this the correct list to post this on?

Best regards,
Matthew Mehrtens

> On Feb 8, 2026, at 15:26, 'Matthew Mehrtens' via Open MPI users 
> <[email protected]> wrote:
> 
> Hi,
> 
> I'm getting a build failure when building Open MPI 5.0.9 with LLVM compilers 
> on macOS (Apple Silicon). Configure succeeds, but make fails when linking:
> 
> ```
> flang-21: error: unknown argument: '-compatibility_version'
> flang-21: error: unknown argument: '-current_version'
> flang-21: error: no such file or directory: '81'
> flang-21: error: no such file or directory: '81.3'
> make[3]: *** [libmpi_usempif08.la] Error 1
> ```
> 
> I believe this error comes from config/ltmain_flang_darwin.diff. The patch 
> has three hunks that add flang-specific handling for Darwin linker flags. 
> Hunks 1 and 3 match against $CC directly using `case $CC in flang*)`, which 
> fails when the Fortran compiler is specified as a full path (e.g., 
> /opt/homebrew/opt/flang/bin/flang). Hunk 2 correctly uses `func_cc_basename 
> $CC` before matching, so it doesn't have this problem.
> 
> Environment:
> macOS 26.2 (Darwin 25.2.0), aarch64 (Apple M1 Pro)
> Homebrew clang/clang++/flang 21.1.8
> Open MPI 5.0.9
> Configure command:
> ```
> $ ./configure \
>       CC=/opt/homebrew/opt/llvm/bin/clang \
>       CPPFLAGS=-I/opt/homebrew/opt/llvm/include \
>       CXX=/opt/homebrew/opt/llvm/bin/clang++ \
>       CXXCPPFLAGS=-I/opt/homebrew/opt/llvm/include \
>       FC=flang \
>       LDFLAGS="-L/opt/homebrew/opt/llvm/lib -L/opt/homebrew/opt/llvm/lib/c++ 
> -L/opt/homebrew/opt/llvm/lib/unwind -lunwind" \
>       --with-hwloc=/opt/homebrew/opt/hwloc \
>       --with-libevent=/opt/homebrew/opt/libevent \
>       --with-pmix=/opt/homebrew/opt/pmix
> ```
> 
> Build output: 
> https://www.icloud.com/iclouddrive/00dSkBghSZdP0-MRsCPN7M7pw#ompi-output (let 
> me know if you cannot access this, and I'll resubmit using a different 
> service)
> 
> Workaround: Use `FC=flang` (bare name) instead of the full path, with 
> /opt/homebrew/opt/flang/bin in $PATH.
> 
> Suggested fix: Update hunks 1 and 3 in config/ltmain_flang_darwin.diff to use 
> `func_cc_basename $CC` and `$func_cc_basename_result` instead of matching $CC 
> directly, consistent with hunk 2.
> 
> If this is indeed a bug and not intentional, I'd be happy to submit an 
> issue/PR on GitHub if you can advise on the preferred approach. I wasn't sure 
> whether to regenerate the diff against a specific libtool version or patch it 
> directly.
> 
> Thanks,
> Matthew Mehrtens
> 
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