packing for GCC

libsipc/include/sipc.h

@@ -28,7 +28,13 @@ typedef enum {
 
 #define _SI_HEADER_CHECK 0xbeefbeefabad1dealu
 
-typedef struct {
+#ifdef __GNUC__
+#define __pack __attribute__((packed))
+#else
+#define __pack
+#endif
+
+typedef struct __pack {
 	union {
 		si_type type;
 		uint32_t __pad;