[FFmpeg-devel] [PATCH][RFC] -std=c99
Tue Aug 12 23:04:57 CEST 2008
Michael Niedermayer <michaelni at gmx.at> writes:
> On Tue, Aug 12, 2008 at 08:56:12PM +0100, M?ns Rullg?rd wrote:
>> Michael Niedermayer <michaelni at gmx.at> writes:
>> > Hi
>> > the patch below adds -std=c99 to the cflags when supported. The
>> > advanatges this has is that the compiler uses C99 semantics, that
>> > several non C99 features and declarations become disabled by
>> > default and thus cannot so easily be used mistakely.
>> > Compilation and regression tests pass for me.
>> > -fasm is needed for
>> > asm()
>> > -D_BSD_SOURCE is needed for
>> > strncasecmp()
>> > inet_aton()
>> > gethostname()
>> > fd_set()
>> > FD_ZERO
>> > FD_SET
>> > FD_ISSET
>> > -D_POSIX_C_SOURCE is needed for:
>> > getaddrinfo()
>> > gai_strerror()
>> > freeaddrinfo()
>> > AI_PASSIVE
>> > getnameinfo()
>> > -D_POSIX_C_SOURCE=2 is needed for:
>> > optind
>> > optarg
>> > getopt()
>> > The defines are likely needed for more than what i have listed
>> > above, these where just amongth the first that showed up without
>> > the specfic option
>> Something like this has been on my low-priority TODO list (i.e. things
>> that I'd like to do, but probably never will) for some time.
>> _POSIX_C_SOURCE and _XOPEN_SOURCE are standard feature selection
>> macros, so using those is preferred over the glibc-specific ones.
>> Setting _BSD_SOURCE is slightly dangerous, since it makes glibc
>> replace a few standard functions with BSD-compatible functions of the
>> same name.
> according to the actual headers
> /* If _BSD_SOURCE was defined by the user, favor BSD over POSIX. */
> #if defined _BSD_SOURCE && \
> !(defined _POSIX_SOURCE || defined _POSIX_C_SOURCE || \
> defined _XOPEN_SOURCE || defined _XOPEN_SOURCE_EXTENDED || \
> defined _GNU_SOURCE || defined _SVID_SOURCE)
> # define __FAVOR_BSD 1
> so because we did define _POSIX_C_SOURCE bsd would not be favored
I forgot about that bit.
> as far as i can see,
That's the trouble with glibc, visibility is very poor.
(Go on Uoti, take that half sentence out of context, and flame a bit.)
> i ve not checked the docs as i dont trust them
I don't trust the docs to be accurate, and I don't trust the headers
to not change. In fact, I don't trust glibc. Nor Ulrich Drepper.
>> Most (all?) of the above-mentioned functions are POSIX standard, so
>> there should be no need for _BSD_SOURCE. If anything does require
>> this, we should look for a POSIX alternative.
> Ill try again with xopen and posix and without bsd
You're racing with Baptiste on this. I recommend both of you hold off
any commits, and send patches first.
mans at mansr.com
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