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

[Bill Spitzak]

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.