From 1fbf220ebc722759cbe69e65f9df5ce44cf71832 Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Thu, 17 Sep 2009 17:16:43 -0400
Subject: [PATCH] Fix CHECK_(C|CXX)_COMPILER_FLAG for Clang

This compiler warns and returns 0 for unrecognized flags.  We fix the
compiler flag check macros by looking for a warning in the output.
See issue #12394.
---
 Modules/CheckCCompilerFlag.cmake   |    1 +
 Modules/CheckCXXCompilerFlag.cmake |    1 +
 2 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/Modules/CheckCCompilerFlag.cmake b/Modules/CheckCCompilerFlag.cmake
index a390b38..ec0a773 100644
--- a/Modules/CheckCCompilerFlag.cmake
+++ b/Modules/CheckCCompilerFlag.cmake
@@ -30,6 +30,7 @@ MACRO (CHECK_C_COMPILER_FLAG _FLAG _RESULT)
      FAIL_REGEX "warning: command line option .* is valid for .* but not for C"
                                                             # Apple gcc
      FAIL_REGEX "unrecognized .*option"                     # GNU
+     FAIL_REGEX "unknown .*option"                          # Clang
      FAIL_REGEX "ignoring unknown option"                   # MSVC
      FAIL_REGEX "warning D9002"                             # MSVC, any lang
      FAIL_REGEX "[Uu]nknown option"                         # HP
diff --git a/Modules/CheckCXXCompilerFlag.cmake b/Modules/CheckCXXCompilerFlag.cmake
index 788bf35..f646e78 100644
--- a/Modules/CheckCXXCompilerFlag.cmake
+++ b/Modules/CheckCXXCompilerFlag.cmake
@@ -28,6 +28,7 @@ MACRO (CHECK_CXX_COMPILER_FLAG _FLAG _RESULT)
    CHECK_CXX_SOURCE_COMPILES("int main() { return 0;}" ${_RESULT}
      # Some compilers do not fail with a bad flag
      FAIL_REGEX "unrecognized .*option"                     # GNU
+     FAIL_REGEX "unknown .*option"                          # Clang
      FAIL_REGEX "ignoring unknown option"                   # MSVC
      FAIL_REGEX "warning D9002"                             # MSVC, any lang
      FAIL_REGEX "[Uu]nknown option"                         # HP
-- 
1.7.6.522.g552fc