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git/builtin/get-tar-commit-id.c
Jeff King 61d36330b4 prefer "!=" when checking read_in_full() result
Comparing the result of read_in_full() using less-than is
potentially dangerous, as a negative return value may be
converted to an unsigned type and be considered a success.
This is discussed further in 561598cfcf (read_pack_header:
handle signed/unsigned comparison in read result,
2017-09-13).

Each of these instances is actually fine in practice:

 - in get-tar-commit-id, the HEADERSIZE macro expands to a
   signed integer. If it were switched to an unsigned type
   (e.g., a size_t), then it would be a bug.

 - the other two callers check for a short read only after
   handling a negative return separately. This is a fine
   practice, but we'd prefer to model "!=" as a general
   rule.

So all of these cases can be considered cleanups and not
actual bugfixes.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-09-27 15:45:24 +09:00

41 lines
960 B
C

/*
* Copyright (c) 2005, 2006 Rene Scharfe
*/
#include "cache.h"
#include "commit.h"
#include "tar.h"
#include "builtin.h"
#include "quote.h"
static const char builtin_get_tar_commit_id_usage[] =
"git get-tar-commit-id";
/* ustar header + extended global header content */
#define RECORDSIZE (512)
#define HEADERSIZE (2 * RECORDSIZE)
int cmd_get_tar_commit_id(int argc, const char **argv, const char *prefix)
{
char buffer[HEADERSIZE];
struct ustar_header *header = (struct ustar_header *)buffer;
char *content = buffer + RECORDSIZE;
const char *comment;
ssize_t n;
if (argc != 1)
usage(builtin_get_tar_commit_id_usage);
n = read_in_full(0, buffer, HEADERSIZE);
if (n != HEADERSIZE)
die("git get-tar-commit-id: read error");
if (header->typeflag[0] != 'g')
return 1;
if (!skip_prefix(content, "52 comment=", &comment))
return 1;
if (write_in_full(1, comment, 41) < 0)
die_errno("git get-tar-commit-id: write error");
return 0;
}