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tempfile: handle NULL tempfile pointers gracefully 

The tempfile functions all take pointers to tempfile
objects, but do not check whether the argument is NULL.
This isn't a big deal in practice, since the lifetime of any
tempfile object is defined to last for the whole program. So
even if we try to call delete_tempfile() on an
already-deleted tempfile, our "active" check will tell us
that it's a noop.

In preparation for transitioning to a new system that
loosens the "tempfile objects can never be freed" rule,
let's tighten up our active checks:

  1. A NULL pointer is now defined as "inactive" (so it will
     BUG for most functions, but works as a silent noop for
     things like delete_tempfile).

  2. Functions should always do the "active" check before
     looking at any of the struct fields.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jeff King 2017-09-05 08:14:40 -04:00 committed by Junio C Hamano
parent e6fc267314
commit f5b4dc7668
2 changed files with 8 additions and 6 deletions
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12
tempfile.c
View File

@ -236,13 +236,15 @@ FILE *get_tempfile_fp(struct tempfile *tempfile)
int close_tempfile_gently(struct tempfile *tempfile)
{
int fd = tempfile->fd;
FILE *fp = tempfile->fp;
int fd;
FILE *fp;
int err;
if (fd < 0)
if (!is_tempfile_active(tempfile) || tempfile->fd < 0)
return 0;
fd = tempfile->fd;
fp = tempfile->fp;
tempfile->fd = -1;
if (fp) {
tempfile->fp = NULL;
@ -262,10 +264,10 @@ int close_tempfile_gently(struct tempfile *tempfile)
int reopen_tempfile(struct tempfile *tempfile)
{
if (0 <= tempfile->fd)
die("BUG: reopen_tempfile called for an open object");
if (!is_tempfile_active(tempfile))
die("BUG: reopen_tempfile called for an inactive object");
if (0 <= tempfile->fd)
die("BUG: reopen_tempfile called for an open object");
tempfile->fd = open(tempfile->filename.buf, O_WRONLY);
return tempfile->fd;
}

2
tempfile.h
View File

@ -211,7 +211,7 @@ extern FILE *fdopen_tempfile(struct tempfile *tempfile, const char *mode);
static inline int is_tempfile_active(struct tempfile *tempfile)
{
return tempfile->active;
return tempfile && tempfile->active;
}
/*