prevent warnings when using the gcc option -Wunreachable-code

lib/mprintf.c

@@ -44,6 +44,11 @@
 #define SIZEOF_LONG_DOUBLE 0
 #endif
 
+#ifndef SIZEOF_SIZE_T
+/* default to 4 bytes for size_t unless defined in the config.h */
+#define SIZEOF_SIZE_T 4
+#endif
+
 #ifdef DPRINTF_DEBUG
 #define HAVE_LONGLONG
 #define LONG_LONG long long
@@ -381,11 +386,12 @@ static long dprintf_Pass1(char *format, va_stack_t *vto, char **endpos,
 	case 'z':
           /* the code below generates a warning if -Wunreachable-code is
              used */
-	  if (sizeof(size_t) > sizeof(unsigned long))
-	    flags |= FLAGS_LONGLONG;
-	  if (sizeof(size_t) > sizeof(unsigned int))
-	    flags |= FLAGS_LONG;
-	  break;
+#if SIZEOF_SIZE_T>4
+          flags |= FLAGS_LONGLONG;
+#else
+          flags |= FLAGS_LONG;
+#endif
+          break;
         case 'O':
 #if SIZEOF_CURL_OFF_T > 4
           flags |= FLAGS_LONGLONG;