From 87cfe7d051441b7a98f4557149daaf7009cb31ec Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Wed, 4 Jul 2018 16:46:32 +1000
Subject: [PATCH] compile_flag: add failure regex

---
 compile_flag.cmake | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/compile_flag.cmake b/compile_flag.cmake
index c6b7007..f6bb622 100644
--- a/compile_flag.cmake
+++ b/compile_flag.cmake
@@ -1,4 +1,5 @@
 include(CheckCXXSourceCompiles)
+include(CMakeCheckCompilerFlagCommonPatterns)
 
 # Test if a compiler flag is supported.
 #
@@ -11,6 +12,12 @@ include(CheckCXXSourceCompiles)
 macro (append_compile_flag _flag)
     string (MAKE_C_IDENTIFIER ${_flag} _name)
 
+    CHECK_COMPILER_FLAG_COMMON_PATTERNS(_append_compile_flag_COMMON_PATTERNS)
+    set(_append_compile_flag_COMMON_PATTERNS
+        ${_append_compile_flag_COMMON_PATTERNS}
+        FAIL_REGEX "argument unused during compilation" #clang
+    )
+
     if (NOT DEFINED compile_flag_${_name})
         # If we have an argument of the form "-Wno-foo" then we can't test it
         # directly as GCC will unconditioally succeed right up until the
@@ -30,7 +37,12 @@ macro (append_compile_flag _flag)
             set(CMAKE_REQUIRED_FLAGS "${CMAKE_CXX_FLAGS} -W${_inverse_flag}")
         endif ()
 
-        check_cxx_source_compiles("int main(int,char**) { return 0; }" compile_flag_${_name})
+        check_cxx_source_compiles(
+            "int main(int,char**) { return 0; }"
+            compile_flag_${_name}
+            ${_append_compile_flag_COMMON_PATTERNS}
+        )
+
         set(CMAKE_REQUIRED_FLAGS "${_append_compile_flag_REQUIRED_FLAGS}")
     endif ()