diff: handle NULs in get_string_hash()

For computing moved lines, we feed the characters of each
line into a hash. When we've been asked to ignore
whitespace, then we pick each character using next_byte(),
which returns -1 on end-of-string, which it determines using
the start/end pointers we feed it.

However our check of its return value treats "0" the same as
"-1", meaning we'd quit if the string has an embedded NUL.
This is unlikely to ever come up in practice since our line
boundaries generally come from calling strlen() in the first
place.

But it was a bit surprising to me as a reader of the
next_byte() code. And it's possible that we may one day feed
this function with more exotic input, which otherwise works
with arbitrary ptr/len pairs.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/diff.c b/diff.c
index 09081a207cdf03bb631dcd814b16d41d58d7ab94..c4a669ffa8690f7640294f717e817352265a8bf6 100644 (file)
--- a/diff.c
+++ b/diff.c
@@ -782,7 +782,7 @@ static unsigned get_string_hash(struct emitted_diff_symbol *es, struct diff_opti
                strbuf_reset(&sb);
                while (ae > ap && isspace(ae[-1]))
                        ae--;
-               while ((c = next_byte(&ap, &ae, o)) > 0)
+               while ((c = next_byte(&ap, &ae, o)) >= 0)
                        strbuf_addch(&sb, c);
 
                return memhash(sb.buf, sb.len);