zzip: string: fix comparison with different signs

When subtracting two pointers, the result is signed as the subtrahend
may point at a position after the minuend, in which case it is bigger
and the result would be negative. This causes a warning in
`_zzip_strnlen`, which is supposed to return an unsigned `size_t`.

As the minuend is computed by using `memchr` on the subtrahend, we know
that it is always either `NULL` or bigger than the subtrahend. And due
to the subtraction only being performed when it is non-`NULL`, we may
simply cast the result to `size_t` to fix the issue, fixing the warning.

diff --git a/zzip/__string.h b/zzip/__string.h
index 4424348aa6531ba3c8b86d144a1a5ebb1622bb2d..e62fb06564cde9155a6fcb36d191230ebaab960f 100644 (file)
--- a/zzip/__string.h
+++ b/zzip/__string.h
@@ -23,7 +23,7 @@ static size_t
 _zzip_strnlen(const char *p, size_t maxlen)
 {
     const char * stop = (char *)memchr(p, '\0', maxlen);
-    return stop ? stop - p : maxlen;
+    return stop ? (size_t)(stop - p) : maxlen;
 }
 #endif