[Openmp-commits] [PATCH] D31055: [OpenMP] libomptarget: Disable on MacOS X

[George Rokos via Phabricator via Openmp-commits]

grokos added inline comments.


================
Comment at: CMakeLists.txt:10
+# there is no point in trying to compile libomptarget on other OSes.
+if (NOT (WIN32 OR ${CMAKE_SYSTEM_NAME} MATCHES "Darwin"))
   add_subdirectory(libomptarget)
----------------
Hahnfeld wrote:
> grokos wrote:
> > Hahnfeld wrote:
> > > Should we do this the other way around and say `CMAKE_SYSTEM_NAME MATCHES "Linux"`?
> > Technically, the plugins' CMakeLists.txt's require that the build system is Linux, however there is no reason I'm aware of why they cannot be built on any Unix system, as long as it supports the ELF executable format (e.g. FreeBSD). So maybe the best choice is to leave the condition above as-is (!win32 && !darwin) and change the plugins' CMakeLists to support general Unices. Any thoughts?
> Darwin is also Unix-like. If I see that correctly, only the linker doesn't support `--version-script` which is only needed for public / private symbols. In that case, it would be best to have a `config-ix.cmake` check and only add the flag in `libomptarget/CMakeLists.txt` and `libomptarget/plugins/CMakeLists.txt` if supported by the building environment.
Darwin is Unix-like, but it does NOT support ELF, it uses Mach-O, so the plugins will not work. E.g. headers `elf.h` and `libelf.h` do not exist on MacOS X.

Besides, if I just omit the version script there are more compilation errors related to undefined references to functions from the host runtime. This is the output I get:

```
[ 94%] Linking C shared library libomp.dylib
[ 94%] Built target omp
Scanning dependencies of target omptarget
[ 97%] Building CXX object libomptarget/CMakeFiles/omptarget.dir/src/omptarget.cpp.o
[100%] Linking CXX shared library libomptarget.dylib
Undefined symbols for architecture x86_64:
  "___kmpc_omp_taskwait", referenced from:
      ___tgt_target_data_begin_nowait in omptarget.cpp.o
      ___tgt_target_data_end_nowait in omptarget.cpp.o
      ___tgt_target_data_update_nowait in omptarget.cpp.o
      ___tgt_target_nowait in omptarget.cpp.o
      ___tgt_target_teams_nowait in omptarget.cpp.o
  "_omp_get_default_device", referenced from:
      ___tgt_target_data_begin in omptarget.cpp.o
      ___tgt_target_data_end in omptarget.cpp.o
      ___tgt_target_data_update in omptarget.cpp.o
      ___tgt_target in omptarget.cpp.o
      ___tgt_target_teams in omptarget.cpp.o
      ___kmpc_push_target_tripcount in omptarget.cpp.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[2]: *** [libomptarget/libomptarget.dylib] Error 1
make[1]: *** [libomptarget/CMakeFiles/omptarget.dir/all] Error 2
make: *** [all] Error 2
```

I guess this is due to the way MacOS handles weak linkage, but I'm not an expert here.



Repository:
  rL LLVM

https://reviews.llvm.org/D31055