Re: autoconf tests and stdcall name mangling

[Eric Blake]

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.

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

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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