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Message-ID: <20141208162509.GI4574@brightrain.aerifal.cx>
Date: Mon, 8 Dec 2014 11:25:09 -0500
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: pthread_equal
On Mon, Dec 08, 2014 at 05:18:41PM +0100, Jörg Krause wrote:
> On Mo, 2014-12-08 at 09:56 -0500, Rich Felker wrote:
> > On Mon, Dec 08, 2014 at 03:42:25PM +0100, Jörg Krause wrote:
> > > Why does musl declares pthread_equal both as macro and as function?
> >
> > C and POSIX allow any of their standard functions to be provided as
> > macros too, but the function definition must always be provided. The
> > reason I put the macro in musl is simply that it's easy to do and
> > gives better code (trivial inline comparison rather than spilling all
> > registers and making a function call) and it's not something where the
> > implementation could change or need to change.
>
> I see! The problem was, that MPD (Music Player Daemon, implemented in C
> ++) for instance used ::pthread_equal(id, other_id) which did not build
> with musl because of the macro expansion.
>
> The maintainer removed the namespace operator to get it work with musl:
> http://git.musicpd.org/cgit/master/mpd.git/commit/?h=v0.18.x&id=d8fc2db910a11dbbba53ba7ecf96d0e32a081076
I see.
For the standard C headers, the C++ versions are supposed to omit the
macros that the C versions might offer. However, there's no such rule
for POSIX headers since there's no formal spec for interaction of C++
and POSIX at all. Perhaps it would be useful to take the same approach
and suppress such macros if __cplusplus is defined, even in the POSIX
headers? But I think from an application portability perspective, they
should either use #undef or parens, i.e. (::pthread_equal)(id1,id2),
instead of assuming there is no macro.
Rich
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