Fix TCL_STACK_GROWS_UP for gcc 4.6

3 files changed, 14 insertions, 4 deletions

diff --git a/ChangeLog b/ChangeLog
index 53b15cf..70860fe 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2011-06-30  Reinhard Max  <max@suse.de>
+
+	* unix/configure.in: Add a volatile declaration to the test for
+	TCL_STACK_GROWS_UP to prevent gcc 4.6 from producing invalid
+	results due to aggressive optimisation.
+
 2011-06-23  Don Porter  <dgp@users.sourceforge.net>
 
 	*** 8.5.10 TAGGED FOR RELEASE ***
diff --git a/unix/configure b/unix/configure
index ed71de0..aa792a7 100755
--- a/unix/configure
+++ b/unix/configure
@@ -18705,10 +18705,12 @@ cat >>conftest.$ac_ext <<_ACEOF
 
 	int StackGrowsUp(int *parent) {
 	    int here;
+	    volatile int result;
 	    if (parent)
-		return (&here < parent);
+		result = (&here < parent);
 	    else
-		return StackGrowsUp(&here);
+		result = StackGrowsUp(&here);
+	    return result;
 	}
 	int main (int argc, char *argv[]) {
 	    return StackGrowsUp(0);
diff --git a/unix/configure.in b/unix/configure.in
index e30c937..3394369 100644
--- a/unix/configure.in
+++ b/unix/configure.in
@@ -705,10 +705,12 @@ AC_CACHE_CHECK([if the C stack grows upwards in memory], tcl_cv_stack_grows_up,
     AC_TRY_RUN([
 	int StackGrowsUp(int *parent) {
 	    int here;
+	    volatile int result;
 	    if (parent)
-		return (&here < parent);
+		result = (&here < parent);
 	    else
-		return StackGrowsUp(&here);
+		result = StackGrowsUp(&here);
+	    return result;
 	}
 	int main (int argc, char *argv[]) {
 	    return StackGrowsUp(0);