[PATCH] Fallback to older detection code if pkg-config can't find expat

[Pekka Paalanen]

On Sat, 31 Jan 2015 10:55:54 -0800
Bill Spitzak <spitzak at gmail.com> wrote:

> On 01/31/2015 04:07 AM, sardemff7+wayland at sardemff7.net wrote:
> > On 2015-01-31 02:23, Bill Spitzak wrote:
> >> On older expat versions there is no pkg-config file, so fall back
> >> to the previous test for the header file and library if it fails.
> >
> > I agree this a good practice to fallback in this case.
> 
> >> This paritally reverts commit
> >> a4afd90f9f0c27ed5f3f313b915c260673f8be34.
> 
> >> -wayland_scanner_CFLAGS = $(EXPAT_CFLAGS) $(AM_CFLAGS)
> >
> > This hunk is bad. If the pkg-config file provide CFLAGS, they must
> > be used. And there is no harm at all to use an undefined variable
> > here. (And I think we should just define it empty in the fallback.)
> 
> I included that by mistake when I did the revert. Will fix.
> 
> >> +        [AC_CHECK_HEADERS(expat.h, [AC_DEFINE(HAVE_EXPAT_H)],
> >
> > HAVE_EXPAT_H is defined by AC_CHECK_HEADERS itself so please remove
> > the AC_DEFINE.
> >
> >
> >> +        [AC_MSG_ERROR([Can't find expat.h. Please install
> >> expat.])])
> >> +    AC_CHECK_LIB(expat, XML_ParserCreate, [EXPAT_LIBS="-lexpat"],
> >
> > If we re-introduce such check, we should use AC_SEARCH_LIBS (as
> > advised by the Autoconf manual[1]).
> > Here is the code I would use :
> >
> >
> > EXPAT_CFLAGS=""
> > EXPAT_LIBS="-lexpat"
> > AC_SEARCH_LIBS([XML_ParserCreate], [expat],
> >    [
> >      AC_SUBST(EXPAT_CFLAGS)
> >      AC_SUBST(EXPAT_LIBS)
> >    ],
> >    [
> >      AC_MSG_ERROR([Can't find expat library. Please install expat.])
> >    ])
> 
> I just reverted the previous patch, but if the non-pkg-config test
> can be improved it probably is a good idea, I will test this and
> submit a new patch.

Bryce,

I don't know if Bill already sent a new patch, but I think this issue
should be dealt with before the 1.7.0 release. If nothing better, just
revert the original patch that removed the "awkward" expat test.

I think we need to keep the non-pkg-config test or fallback working
until we start requiring an expat version that provides the .pc file
upstream.


Thanks,
pq