Date: Tue, 29 Sep 1998 16:14:51 +0400 From: Dmitrij Tejblum <tejblum@arc.hq.cti.ru> To: Bruce Evans <bde@zeta.org.au> Cc: dg@root.com, shmit@kublai.com, wb@yorikke.arb-phys.uni-dortmund.de, freebsd-bugs@FreeBSD.ORG Subject: Re: bin/7742: fclose(3) dumps core on NULL Message-ID: <199809291214.QAA23755@arc.hq.cti.ru> In-Reply-To: Your message of "Tue, 29 Sep 1998 09:47:01 %2B1000." <199809282347.JAA18084@godzilla.zeta.org.au>
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Bruce Evans wrote:
> >Why is free(NULL) permissable, but not fclose(NULL)?
>
> Because the C standard says so.
Well, a program calling fclose(NULL) is non-conforming. And what? A lot of
non-conforming programs work on FreeBSD. Anyhow, the behavior of
printf("%s", (char*)NULL) is not defined by the standard too, but on
FreeBSD this print "(null)" rather than dumps core. IMO, this is far more
bogus, and I'd rather remove this feature.
Anyway, fclose(NULL) is not like strlen(NULL) or fprintf(NULL, ...).
fclose(NULL) is like free(NULL), and I claim that it is in the spirit of C
if fclose(NULL) permitted :-| :-|. (It is definitely in the spirit of C++,
and the standard C library is a part of the standard C++ library.)
Note that FreeBSD is apparently the only modern Unix that doesn't permit
fclose(NULL), thus the programmer doesn't need to "know about this problem":
fixing his code doesn't buy him portability to anything else. This "problem"
is FreeBSD-specific in practice, and we should remove it as such. (*)
Also, it is irrelevant that programmers don't test result of fclose(NULL).
fclose(NULL) simple should not be considered as a bug, just like free(NULL).
Appendix. OS comparison.
FreeBSD Linux Solaris OSF/1
N/A 2.5 3.0
fclose(NULL) core work work work
fprintf(NULL, "Hi") core work core core
printf("%s", (char*)NULL) work work core work
IMO, Solaris' behavior is (most) correct.
Dima
(*) Apparently, most (or all) Windows compilers do not permit fclose(NULL).
It is totally irrelevant, though. :-)
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