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Re: mbstate_t on HP-UX 11.11


From: Eric Blake
Subject: Re: mbstate_t on HP-UX 11.11
Date: Sat, 20 Dec 2008 09:13:26 -0700
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According to Bruno Haible on 12/20/2008 7:40 AM:
> Indeed. The mbstate_t type and mbsinit etc. functions were not part of
> C89 + appendices, they were introduced in C99. Therefore, the
> -D_XOPEN_SOURCE=500 option should better be added to the detection of flags
> for C99, not C89. (But be careful to use it only for HP-UX! On other systems,
> this flag is very likely to cause damage.)
> 
> OTOH, AC_PROG_CC (which is what nearly every packages uses) assumes the
> user wants C89, not C99. Hmm?

Actually, it doesn't even assume that, yet.  As has been discussed on the
list in the past, AC_PROG_CC still supports K&R by default.  We've talked
about changing things, so that C89 is default and you have to be explicit
to get K&R, but no one has written the patch yet.

On the other hand, the fact that C89 does not define mbstate_t seems to
answer the question.  We need to guarantee that AC_USE_SYSTEM_EXTENSIONS
(which works regardless of C flavor) and AC_PROG_CC_C99 both guarantee the
define, then applications that explicitly ask for extensions, as well as
applications that explicitly ask for C99, will get what they need.  We can
also add a paragraph in the autoconf manual mentioning that mbstate_t is
not guaranteed by the default AC_PROG_CC, and that you need either (or
both) AC_USE_SYSTEM_EXTENSIONS or AC_PROG_CC_C99.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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