From 74d7ba276ec7a82e04faf554cc1c7c39455f6141 Mon Sep 17 00:00:00 2001
From: Magne Sjaastad <magne.sjaastad@ceetronsolutions.com>
Date: Tue, 15 Apr 2014 09:48:32 +0200
Subject: [PATCH] Test if variable is defined before executing GCC test

---
 CMakeLists.txt | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 590b6d0b72..c32423b2a5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -99,14 +99,19 @@ find_package( OpenGL )
 # Allow use of non-threadsafe reference counter in cvf::Object on systems with no atomics support
 if (CMAKE_COMPILER_IS_GNUCC)
  
-    check_c_source_compiles("int main(int argc, char **argv) {
-        int a;
-        __sync_add_and_fetch(&a, 1);
-        __sync_fetch_and_add(&a, 1);
-        __sync_sub_and_fetch(&a, 1);
-        __sync_fetch_and_sub(&a, 1); }" HAVE_GCC_ATOMICS)
+    if (NOT DEFINED HAVE_GCC_ATOMICS)
+        check_c_source_compiles("int main(int argc, char **argv) {
+            int a;
+            __sync_add_and_fetch(&a, 1);
+            __sync_fetch_and_add(&a, 1);
+            __sync_sub_and_fetch(&a, 1);
+            __sync_fetch_and_sub(&a, 1); }" HAVE_GCC_ATOMICS)
+    endif()
  
-    if (NOT HAVE_GCC_ATOMITCS)
+    if (HAVE_GCC_ATOMICS)
+        message("Atomics supported")
+    else()
+        message("Atomics not supported")
         add_definitions(-DCVF_WORKAROUND_TO_COMPILE_ON_SYSTEMS_WITHOUT_ATOMICS)
     endif()