convert bare readlink to strbuf_readlink

This particular readlink call never NUL-terminated its
result, making it a potential source of bugs (though there
is no bug now, as it currently always respects the length
field). Let's just switch it to strbuf_readlink which is
shorter and less error-prone.

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 f06876be67245ab559b57168553cfd71b9d23feb..dcfbcb0215766efefa786b18d793c4bf96740b8c 100644 (file)
--- a/diff.c
+++ b/diff.c
@@ -2014,18 +2014,15 @@ static struct diff_tempfile *prepare_temp_file(const char *name,
                        die("stat(%s): %s", name, strerror(errno));
                }
                if (S_ISLNK(st.st_mode)) {
-                       int ret;
-                       char buf[PATH_MAX + 1]; /* ought to be SYMLINK_MAX */
-                       ret = readlink(name, buf, sizeof(buf));
-                       if (ret < 0)
+                       struct strbuf sb = STRBUF_INIT;
+                       if (strbuf_readlink(&sb, name, st.st_size) < 0)
                                die("readlink(%s)", name);
-                       if (ret == sizeof(buf))
-                               die("symlink too long: %s", name);
-                       prep_temp_blob(name, temp, buf, ret,
+                       prep_temp_blob(name, temp, sb.buf, sb.len,
                                       (one->sha1_valid ?
                                        one->sha1 : null_sha1),
                                       (one->sha1_valid ?
                                        one->mode : S_IFLNK));
+                       strbuf_release(&sb);
                }
                else {
                        /* we can borrow from the file in the work tree */