[PATCH] D135402: [LLD] Enable --no-undefined-version by default.

[Joseph Huber via Phabricator via llvm-commits]

jhuber6 added a comment.

In D135402#3857039 <https://reviews.llvm.org/D135402#3857039>, @MaskRay wrote:

> AFAICT openmp uses an incorrect version script where some exact patterns don't match symbols. This is error-prone but before this default switch it was unnoticed.

Yes, I originally attempted to rectify the offending version scripts. The only difficult one to rectify is the one for `libomp`. This is because some symbols are only defined in a debug build, or some other configuration, it contains lines like this.

  #if USE_DEBUGGER
          __kmp_debugging;
          __kmp_omp_debug_struct_info;
  #endif /* USE_DEBUGGER */

What would you suggest for solving this? Should we just include dummy symbols in the case that these symbols aren't included?

Also, I mentioned previously in this thread the errors I was getting with the `lto` version script. Do you happen to know why these aren't defined?

  diff --git a/llvm/tools/lto/lto.exports b/llvm/tools/lto/lto.exports
  index 3abae5f0fcba..4164c3919a97 100644
  --- a/llvm/tools/lto/lto.exports
  +++ b/llvm/tools/lto/lto.exports
  @@ -45,12 +45,6 @@ lto_codegen_compile_optimized
   lto_codegen_set_should_internalize
   lto_codegen_set_should_embed_uselists
   lto_set_debug_options
  -LLVMCreateDisasm
  -LLVMCreateDisasmCPU
  -LLVMDisasmDispose
  -LLVMDisasmInstruction
  -LLVMSetDisasmOptions
  -LLVMCreateDisasmCPUFeatures
   thinlto_create_codegen
   thinlto_codegen_dispose
   thinlto_codegen_add_module

> If you use `--no-undefined-version` with GNU ld, you likely get similar errors.
>
> "drop-in replacement" does not mean ld.lld copies every behavior of GNU ld. We consider many factors and what default makes the most sense.
> I've made comments why the new default makes more sense and I don't want to repeat.

I'm fine with the philosophy and this patch, but I don't want the OpenMP builds to be totally broken until we fix it.


Repository:
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  https://reviews.llvm.org/D135402/new/

https://reviews.llvm.org/D135402