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prefer "!=" when checking read_in_full() result

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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>
This commit is contained in:
Jeff King
2017-09-27 02:00:28 -04:00
committed by Junio C Hamano
parent a1f3515da7
commit 61d36330b4
3 changed files with 3 additions and 3 deletions
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2
builtin/get-tar-commit-id.c
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@ -26,7 +26,7 @@ int cmd_get_tar_commit_id(int argc, const char **argv, const char *prefix)
usage(builtin_get_tar_commit_id_usage);
n = read_in_full(0, buffer, HEADERSIZE);
if (n < HEADERSIZE)
if (n != HEADERSIZE)
die("git get-tar-commit-id: read error");
if (header->typeflag[0] != 'g')
return 1;