[PATCH] D73139: [LLD][COFF] Enable linking of __declspec(selectany) symbols from Clang and GCC

[Reid Kleckner via Phabricator via llvm-commits]

rnk added a comment.

In D73139#1832396 <https://reviews.llvm.org/D73139#1832396>, @mstorsjo wrote:

> This needs a testcase. Have a look in lld/test/COFF, it's probably most suitable with a `.s` test for this (the main test file itself simulating the object file created by e.g. clang, and then either a separate file in test/COFF/Inputs, or generating that second file with echo statements within the file (there's a few examples of this among the existing tests), for the other file - assemble both and try to link them together.


That sounds right to me. You know, I wonder if this would work for test structure:

  # RUN: llvm-mc %s -defsym obj=1 -filetype=obj -o %t1.obj
  # RUN: llvm-mc %s -defsym obj=2 -filetype=obj -o %t2.obj
  # RUN: lld-link ... %t1.obj %t2.obj
  
  .if obj=1
  # obj1 contents
  .endif
  
  .if obj2
  # obj2 contents
  .endif

I haven't tried it, but `.if` seems nicer than echo escapes.



================
Comment at: lld/COFF/InputFiles.cpp:511
+                         leaderSelection == IMAGE_COMDAT_SELECT_ANY))) {
+    leaderSelection = selection = IMAGE_COMDAT_SELECT_ANY;
+  }
----------------
Does ld.bfd implement the same size check? If so, it might be more conservative to use IMAGE_COMDAT_SELECT_SAME_SIZE for the leader.

I see that GCC only allows this attribute to apply to data, not code, so "same size" makes sense, even if it ignores that "selectany" really means IMAGE_COMDAT_SELECT_ANY. :)


Repository:
  rLLD LLVM Linker

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  https://reviews.llvm.org/D73139/new/

https://reviews.llvm.org/D73139