20 Sep
2017
20 Sep
'17
9:13 a.m.
On Tue, Sep 19, 2017 at 01:56:48PM -0400, Random832 wrote:
On Tue, Sep 19, 2017, at 09:56, Larry McVoy wrote:
Thanks for that insight. That code has been working for decades but I
think the reason it works is if it works then errno doesn't change and
if it doesn't work then we're not going to see the output. So passing
save is technically correct but not sure it is practically correct.
Anyone have an opinion?
On Tue, Sep 19, 2017 at 03:53:59PM +0200, Steffen
Nurpmeso wrote:
I think his point was that you should be passing save (rather than
errno) to the strerror and the last printf, because the preceding
library calls may have changed errno. |void
|my_perror(char *file, int line, char *msg)
|{
| char *p = 0;
| int save = errno;
|
| if (p = getenv("_BK_VERSION")) {
| if (strneq(p, "bk-", 3)) p += 3;
| fprintf(stderr, "%s:%d (%s): ", file, line, p);
|} else {
| fprintf(stderr, "%s:%d: ", file, line);
|}
| if (p = strerror(errno)) {
| fprintf(stderr, "%s: %s\n", msg, p);
|} else {
| fprintf(stderr, "%s: errno=%d\n", msg, errno);
|}
| errno = save;
|}
|
|libc should do that.
That really made me wonder why "save" is not used, errno may
eventually change along the way. Ok ok, but.. well.
Huh? save is set with errno and then errno is restored to save. The
point of save is to do the library calls (which do syscalls which
could in theory change errno) and leave it the same as it was on
the way in.