mirror/ git
1
0
Fork 0
mirror of https://github.com/git/git.git synced 2024-04-28 10:55:11 +02:00
Code

tempfile: avoid "ferror | fclose" trick 

The current code wants to record an error condition from
either ferror() or fclose(), but makes sure that we always
call both functions. So it can't use logical-OR "||", which
would short-circuit when ferror() is true. Instead, it uses
bitwise-OR "|" to evaluate both functions and set one or
more bits in the "err" flag if they reported a failure.

Unlike logical-OR, though, bitwise-OR does not introduce a
sequence point, and the order of evaluation for its operands
is unspecified. So a compiler would be free to generate code
which calls fclose() first, and then ferror() on the
now-freed filehandle.

There's no indication that this has happened in practice,
but let's write it out in a way that follows the standard.

Noticed-by: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jeff King 2017-02-16 16:31:40 -05:00 committed by Junio C Hamano
parent c3808ca698
commit 0838cbc22f
1 changed files with 2 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
tempfile.c
View File

@ -247,12 +247,8 @@ int close_tempfile(struct tempfile *tempfile)
tempfile->fd = -1;
if (fp) {
tempfile->fp = NULL;
/*
* Note: no short-circuiting here; we want to fclose()
* in any case!
*/
err = ferror(fp) | fclose(fp);
err = ferror(fp);
err |= fclose(fp);
} else {
err = close(fd);
}