[CMake] Don't trust compiler error code, also check for errors

[beanz]

Summary

rnk reported that MSVC ignores unknown flags and still returns 0. This should cause unknown flags to be an error during the compiler check.

[rnk]

cmake/Modules/BuiltinTests.cmake

1 ↗

(On Diff #66363)

That was also my first thought, but the file has this comment:

# Do NOT include this module directly into any of your code. It is meant as
# a library for Check*CompilerFlag.cmake modules. It's content may change in
# any way between releases.

Think we should do it anyway?

44 ↗

(On Diff #66363)

I think you meant if ("${var}" STREQUAL "FAIL_REGEX")

[beanz]

cmake/Modules/BuiltinTests.cmake

1 ↗

(On Diff #66363)

My gut is to include it anyway. The alternative is to mimic what it does. @brad.king might have thoughts. Despite saying that, the macro's structure hasn't really changed ever.

44 ↗

(On Diff #66363)

Duh...

[beanz]

Updates based on feedback from rnk.

[rnk]

Thanks for dealing with that!

cmake/Modules/BuiltinTests.cmake

2 ↗

(On Diff #66367)

We can duplicate the relevant parts when and if it breaks.

compiler-rt/trunk/cmake/Modules/BuiltinTests.cmake

+include(CMakeCheckCompilerFlagCommonPatterns)
 
 # This function takes an OS and a list of architectures and identifies the
 # subset of the architectures list that the installed toolchain can target.
 function(try_compile_only output)
   set(SIMPLE_C ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/src.c)
   file(WRITE ${SIMPLE_C} "int foo(int x, int y) { return x + y; }\n")
   string(REGEX MATCHALL "<[A-Za-z0-9_]*>" substitutions
          ${CMAKE_C_COMPILE_OBJECT})
function(try_compile_only output)
   string(REPLACE " " ";" test_compile_command "${test_compile_command}")
 
   execute_process(
     COMMAND ${test_compile_command}
     RESULT_VARIABLE result
     OUTPUT_VARIABLE TEST_OUTPUT
     ERROR_VARIABLE TEST_ERROR
   )
-  if(result EQUAL 0)
+
+  CHECK_COMPILER_FLAG_COMMON_PATTERNS(_CheckCCompilerFlag_COMMON_PATTERNS)
+  foreach(var ${_CheckCCompilerFlag_COMMON_PATTERNS})
+    if("${var}" STREQUAL "FAIL_REGEX")
+      continue()
+    endif()
+    if("${var}" MATCHES "${_CheckCCompilerFlag_COMMON_PATTERNS}")
+      set(ERRORS_FOUND True)
+    endif()
+  endforeach()
+
+  if(result EQUAL 0 AND NOT ERRORS_FOUND)
     set(${output} True PARENT_SCOPE)
   else()
     file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
         "Testing compiler for supporting " ${ARGN} ":\n"
         "Command: ${test_compile_command}\n"
         "${TEST_OUTPUT}\n${TEST_ERROR}\n${result}\n")
     set(${output} False PARENT_SCOPE)
   endif()