1 files changed, 10 insertions, 3 deletions
diff --git a/pack.c b/pack.c
index 1300e43b5d..644ffd947a 100644
--- a/pack.c
+++ b/pack.c
@@ -100,9 +100,16 @@ TOKEN_PASTE(swap,x)(xtype z)		\
     return r;				\
 }
 
-#if GCC_VERSION_SINCE(4,3,0)
-# define swap32(x) __builtin_bswap32(x)
-# define swap64(x) __builtin_bswap64(x)
+#ifndef swap32
+# if GCC_VERSION_SINCE(4,3,0)
+#  define swap32(x) __builtin_bswap32(x)
+# endif
+#endif
+
+#ifndef swap64
+# if GCC_VERSION_SINCE(4,3,0)
+#  define swap64(x) __builtin_bswap64(x)
+# endif
 #endif
 
 #ifndef swap16