diff -ru mesa.orig/progs/demos/engine.c mesa/progs/demos/engine.c
--- mesa.orig/progs/demos/engine.c	2008-01-21 14:44:56.000000000 +0000
+++ mesa/progs/demos/engine.c	2008-01-21 14:44:04.000000000 +0000
@@ -15,6 +15,10 @@
 #include "readtex.h"
 #include "trackball.h"
 
+#if !M_PI
+#define M_PI 3.14159265358979323846
+#endif
+
 #define DEG_TO_RAD(DEG)  ((DEG) * M_PI / 180.0)
 
 #define TEXTURE_FILE "../images/reflect.rgb"
diff -ru mesa.orig/progs/xdemos/corender.c mesa/progs/xdemos/corender.c
--- mesa.orig/progs/xdemos/corender.c	2008-01-21 14:44:56.000000000 +0000
+++ mesa/progs/xdemos/corender.c	2008-01-21 14:44:04.000000000 +0000
@@ -25,6 +25,10 @@
 #include <unistd.h>
 #include "ipc.h"
 
+#if !M_PI
+#define M_PI 3.14159265358979323846
+#endif
+
 static int MyID = 0;  /* 0 or 1 */
 static int WindowID = 0;
 static GLXContext Context = 0;