MSVC doesn't like a definition in a for() loop.

src/libsodium/crypto_generichash/blake2/ref/blake2s-ref.c

@@ -132,9 +132,11 @@ static inline int blake2s_param_set_personal( blake2s_param *P, const uint8_t pe
 
 static inline int blake2s_init0( blake2s_state *S )
 {
+  int i;
+
   memset( S, 0, sizeof( blake2s_state ) );
 
-  for( int i = 0; i < 8; ++i ) S->h[i] = blake2s_IV[i];
+  for( i = 0; i < 8; ++i ) S->h[i] = blake2s_IV[i];
 
   return 0;
 }
@@ -301,6 +303,7 @@ int blake2s_update( blake2s_state *S, const uint8_t *in, uint64_t inlen )
 int blake2s_final( blake2s_state *S, uint8_t *out, uint8_t outlen )
 {
   uint8_t buffer[BLAKE2S_OUTBYTES];
+  int     i;
 
   if( S->buflen > BLAKE2S_BLOCKBYTES )
   {
@@ -315,7 +318,7 @@ int blake2s_final( blake2s_state *S, uint8_t *out, uint8_t outlen )
   memset( S->buf + S->buflen, 0, 2 * BLAKE2S_BLOCKBYTES - S->buflen ); /* Padding */
   blake2s_compress( S, S->buf );
 
-  for( int i = 0; i < 8; ++i ) /* Output full hash to temp buffer */
+  for( i = 0; i < 8; ++i ) /* Output full hash to temp buffer */
     store32( buffer + sizeof( S->h[i] ) * i, S->h[i] );
 
   memcpy( out, buffer, outlen );