-#if (PLATFORM_BYTE_ORDER == IS_LITTLE_ENDIAN)
-#define bsw_32(p,n) \
- { int _i = (n); while(_i--) ((uint32_t*)p)[_i] = bswap_32(((uint32_t*)p)[_i]); }
+/* The macros __BYTE_ORDER__ and __ORDER_*_ENDIAN__ are GNU C
+ * extensions. They are also supported by clang as of v3.2 */
+
+#ifdef __BYTE_ORDER__
+# if (__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__)
+# define bsw_32(p,n) \
+ { int _i = (n); while(_i--) ((uint32_t*)p)[_i] = bswap_32(((uint32_t*)p)[_i]); }
+# elif (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
+# define bsw_32(p,n)
+# else
+# error "unknown byte order"
+# endif