[PATCH] D39274: Fix -fuse-ld feature detection error.

[Rui Ueyama via Phabricator via llvm-commits]

ruiu created this revision.
Herald added a subscriber: mgorny.

check_cxx_compiler_flag doesn't seem to try to link a program, so
the existing code doesn't correctly detect the availability of a given
linker.  This patch uses check_cxx_source_compiles instead.

I confirmed that cmake now reports this error

  Host compiler does not support '-fuse-ld=foo'

for -DLLVM_USE_LINKER=foo.


https://reviews.llvm.org/D39274

Files:
  llvm/cmake/modules/HandleLLVMOptions.cmake


Index: llvm/cmake/modules/HandleLLVMOptions.cmake
===================================================================
--- llvm/cmake/modules/HandleLLVMOptions.cmake
+++ llvm/cmake/modules/HandleLLVMOptions.cmake
@@ -194,10 +194,13 @@
 endif()
 
 if( LLVM_USE_LINKER )
-  check_cxx_compiler_flag("-fuse-ld=${LLVM_USE_LINKER}" CXX_SUPPORTS_CUSTOM_LINKER)
+  set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
+  set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fuse-ld=${LLVM_USE_LINKER}")
+  check_cxx_source_compiles("int main() { return 0; }" CXX_SUPPORTS_CUSTOM_LINKER)
   if ( NOT CXX_SUPPORTS_CUSTOM_LINKER )
 	  message(FATAL_ERROR "Host compiler does not support '-fuse-ld=${LLVM_USE_LINKER}'")
   endif()
+  set(CMAKE_REQUIRED_FLAGS ${OLD_CMAKE_REQUIRED_FLAGS})
   append("-fuse-ld=${LLVM_USE_LINKER}"
     CMAKE_EXE_LINKER_FLAGS CMAKE_MODULE_LINKER_FLAGS CMAKE_SHARED_LINKER_FLAGS)
 endif()


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