[Qemu-devel] [PATCH] Improve gcc 3 checking

[Anthony Liguori <aliguori@cs.utexas.edu>]

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In Xen, we use a single top level Makefile to build everything.  This 
means we automatically kick off the configure script.  It would be nice 
if QEMU's configure did a better job of finding existing GCC 3.x 
installs so that the user didn't have to manually specific the location.

The attached patch adds a white list to configure to check for various 
versions of GCC 3.x.  The white list so far covers the various versions 
of GCC in recent versions of OpenSUSE, Fedora, RHEL, and Ubuntu 
(presumably also Debian).

I don't think this patch will impact any of the other platforms but 
getting some testing first on weird platforms (Solaris and Win32 
especially) would be helpful.

Regards,

Anthony Liguori

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diff -r ca36b7b88df2 configure
--- a/configure	Mon Dec 18 18:57:19 2006 -0600
+++ b/configure	Mon Dec 18 20:18:01 2006 -0600
@@ -22,6 +22,7 @@ static="no"
 static="no"
 cross_prefix=""
 cc="gcc"
+gcc3_list="gcc32 gcc33 gcc34 gcc-3.2 gcc-3.3 gcc-3.4"
 host_cc="gcc"
 ar="ar"
 make="make"
@@ -311,6 +312,41 @@ if test "$mingw32" = "yes" ; then
     oss="no"
     if [ "$cpu" = "i386" ] ; then
         kqemu="yes"
+    fi
+fi
+
+# Check for gcc4, error if pre-gcc4 
+if test "$check_gcc" = "yes" ; then
+    cat > $TMPC <<EOF
+#if __GNUC__ < 4
+#error gcc3
+#endif
+int main(){return 0;}
+EOF
+    check_cc() {
+	which "$1" >&/dev/null
+	return $?
+    }
+
+    if check_cc "$cc" ; then
+	echo "WARNING: \"$cc\" looks like gcc 4.x"
+	echo "Looking for gcc 3.x"
+	found_compat_cc="no"
+	for compat_cc in $gcc3_list ; do
+	    if check_cc "$compat_cc" ; then
+		echo "Found \"$compat_cc\""
+		cc="$compat_cc"
+		found_compat_cc="yes"
+		break
+	    fi
+	done
+	if test "$found_compat_cc" = "no" ; then
+	    echo "gcc 3.x not found!"
+	    echo "QEMU is known to have problems when compiled with gcc 4.x"
+	    echo "It is recommended that you use gcc 3.x to build QEMU"
+	    echo "To use this compiler anyway, configure with --disable-gcc-check"
+	    exit 1;
+	fi
     fi
 fi
 
@@ -414,23 +450,6 @@ have_gcc3_options="no"
 have_gcc3_options="no"
 if $cc -fno-reorder-blocks -fno-optimize-sibling-calls -o $TMPO $TMPC 2> /dev/null ; then
    have_gcc3_options="yes"
-fi
-
-# Check for gcc4, error if pre-gcc4 
-if test "$check_gcc" = "yes" ; then
-    cat > $TMPC <<EOF
-#if __GNUC__ < 4
-#error gcc3
-#endif
-int main(){return 0;}
-EOF
-    if $cc -o $TMPO $TMPC 2>/dev/null ; then
-        echo "ERROR: \"$cc\" looks like gcc 4.x"
-        echo "QEMU is known to have problems when compiled with gcc 4.x"
-        echo "It is recommended that you use gcc 3.x to build QEMU"
-        echo "To use this compiler anyway, configure with --disable-gcc-check"
-        exit 1;
-    fi
 fi
 
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