Mark tau and sigma Chacha variables as nonstring

These contain a sequence of bytes, and are not a NUL-terminated string.
Help the compiler understand the intent of the code.

diff --git a/src/chacha_private.h b/src/chacha_private.h
index ef1b931e05ed730785de36dd1a565acd698c61aa..97e9020a20efb0cad130874393532077d27b6a21 100644 (file)
--- a/src/chacha_private.h
+++ b/src/chacha_private.h
@@ -48,8 +48,16 @@ typedef struct
   a = PLUS(a,b); d = ROTATE(XOR(d,a), 8); \
   c = PLUS(c,d); b = ROTATE(XOR(b,c), 7);
 
-static const char sigma[16] = "expand 32-byte k";
-static const char tau[16] = "expand 16-byte k";
+#if defined(__has_attribute)
+#if __has_attribute(__nonstring__)
+#define ATTRIBUTE_NONSTRING __attribute__((__nonstring__))
+#else
+#define ATTRIBUTE_NONSTRING
+#endif
+#endif
+
+static const char sigma[16] ATTRIBUTE_NONSTRING = "expand 32-byte k";
+static const char tau[16] ATTRIBUTE_NONSTRING = "expand 16-byte k";
 
 static void
 chacha_keysetup(chacha_ctx *x,const u8 *k,u32 kbits)