Re: *-config programs and multi-arch

[Miles Bader <miles@gnu.org>]

Adam Borowski <kilobyte@angband.pl> writes:
>> > AFAICT, the easiest way to handle all this is just to make a missing
>> > cross-pkg-config look like a missing pkg-config to the configure
>> > script.  Then whatever logic the script may have for detecting the
>> > "not pkg-config at all" case, will do the right thing for the cross
>> > case too.
>> 
>> Currently I just have my configure script completely disable use of
>> pkg-config when cross-compiling (by setting PKG_CONFIG=""), but
>> obviously this is undesirable if a cross-version of pkg-config was
>> actually found...
>
> How can you link to libraries that require special handling then? 
> Do you hard-code the compiler/linker arguments?  That seems fragile,
> especially with library/include paths changing weekly these days.

I'm a little confused as to what your saying here; what seems fragile?

Are you saying that "pkg-config is necessary in some cases because
some libraries use wacky magic that only pkg-config can provide, so a
non-pkg-config fallback in configure will be hard to make work"?

If so, that's certainly true, but I'm not sure how it affects my
argument -- for libraries where pkg-config is necessary, the current
cross-compiling behavior when a cross-pkg-config isn't found is still
almost certainly the wrong thing.

[If, on the other hand, you're really just asking what I do in the
case where pkg-config isn't present, I mostly just assume the
pkg-config-using libraries aren't present either (they're all
optional); for a few important ones, I fallback to traditional
autoconf methods like AC_CHECK_LIB... some libraries, after all, are
simple enough that this works fine.]

My argument in this thread is just:

   When cross-compiling, there shouldn't be any default fallback for
   pkg-config if a cross-pkg-config (${ARCH}-pkg-config) isn't found;
   the current default behavior is more harmful than useful.

   configure files that _depend_ on pkg-config being present (and
   don't use extra magic like you describe), should simply give a
   fatal error after PKG_PROG_PKG_CONFIG in the case where
   PKG_CONFIG="" (but then, they should do this already, to handle the
   case where the system simply has no pkg-config installed at all).

-Miles

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