Re: autoconf tests and stdcall name mangling

[Dimitrios Apostolou]

On Wed, 22 May 2013, Eric Blake wrote:
> On 05/22/2013 02:12 PM, Zack Weinberg wrote:
> > On Wed, May 22, 2013 at 1:06 PM, Nick Bowler <address@hidden> wrote:
> > > The fundamental problem, I think, is that you really need the proper
> > > headers included and AC_REPLACE_FUNCS does not seem to allow you to
> > > specify the includes.  So you probably can't use this macro at all.
> > >
> > > You can use AC_LINK_IFELSE to fully specify the test program to compile
> > > and link, which is probably what you'll need to do here.  This may still
> > > be tricky to get right.  Alternately, Gnulib[1] has a getaddrinfo module[2]
> > > which may already do everything you need (although I have not used it).
> >
> > I wrote the attached macro to solve a closely related problem (looking
> > for ntohl, not getaddrinfo; the way Winsock works, it's equivalent).
> > Perhaps it will be useful to you.
> >
> > Going forward I think AC_*_FUNC[S] really need to grow a way to
> > specify headers.  Fake-declaring everything as "char foo();" has been
> > kinda silly for years now.
>
> AC_CHECK_DECL ("can I compile against this function when using the right
> headers") is a much better macro than AC_CHECK_FUNC ("can I link against
> this symbol, and cross-my-fingers that the library actually exported it
> by this name and not some other due to aliasing or stdcall or ...").
> There are still a few corner cases where some platforms accidentally
> declare a function but fail to export it, so both styles of probes are
> still useful in practice; but generally you should try the DECL form first.

The way I'm using autoconf up to now, I first do an AC_CHECK_DECLS and 
right afterwards AC_REPLACE_FUNCS. For this case I'll only use 
AC_CHECK_DECLS, thanks everyone for helping. :-)

> Maybe this warrants a patch to the autoconf manual to point this out
> more emphatically; anyone want to take a stab at it?

The AC_REPLACE_FUNCS comes in really handy, so I believe it should be 
updated if AC_CHECK_FUNC is not the recommended way to replace 
non-existing functions.


Thanks,
Dimitris