Short cut zero size to avoid notnull attribute for mmemove in glibc.

Reported-By:	OSS-Fuzz issue 497

diff --git a/libarchive/archive_string.c b/libarchive/archive_string.c
index 592ead2bdd58bc7d6346ce814f07eca9b57b047c..ca39c069ab61ebcb261da821eb8c013452679a40 100644 (file)
--- a/libarchive/archive_string.c
+++ b/libarchive/archive_string.c
@@ -200,6 +200,8 @@ static int archive_string_append_unicode(struct archive_string *,
 static struct archive_string *
 archive_string_append(struct archive_string *as, const char *p, size_t s)
 {
+       if (s == 0)
+               return (as);
        if (archive_string_ensure(as, as->length + s + 1) == NULL)
                return (NULL);
        memmove(as->s + as->length, p, s);