[libvirt] [PATCH] Update LIBVIRT_CHECK_LIB and LIBVIRT_CHECK_LIB_ALT to use pkg-config

[Eric Blake]

On 12/04/2014 03:36 PM, Pavel Hrdina wrote:
> On 12/04/2014 09:41 PM, Eric Blake wrote:
>> On 12/04/2014 01:30 PM, Pavel Hrdina wrote:
>>> For example on FreeBSD the "yajl" library is located at "/usr/local/lib"
>>> and it's not in default LIBS and therefore the configure fails that
>>> "yajl" not installed.
>>>
>>> We can use the "PKG_CHECK_MODULES" to get the correct library path in
>>> case the library provides pkg-config file definition, otherwise the old
>>> approach is used.
>>
>> This feels a bit awkward.  Shouldn't we instead be fixing
>> m4/virt-yajl.m4 to use LIBVIRT_CHECK_PKG?  That is, shouldn't yajl be
>> using pkg-config everywhere, and not just on FreeBSD?
>>
> 
> Hi, it will use the pkg-config everywhere. I don't know the exact
> reason why yajl and sasl don't use the LIBVIRT_CHECK_PKG but it seems
> that it's because we support two different major versions of yajl and
> the have some changes in API and ABI so we have to check which version
> is installed in the system and define appropriate macros.
> 
> See the 'src/util/virjson.c' that we have "WITH_YAJL" and "WITH_YAJL2".
> The LIBVIRT_CHECK_PKG doesn't count with the possibility of alternative
> versions of libraries.

Hmm, I wonder if we can reuse some of the logic currently in
configure.ac that probes whether gnutls is at version 2.x or 3.x by
directly probing '$PKG_CONFIG --exists ...', and then going on to
PKG_CHECK_MODULES once we know which of the two library flavors we are
dealing with.  That is, I still think we are better off patching
virt/m4-yajl.m4 (the one library where we know we have pkg_config
information, but aren't using it right) than changing virt/m4-lib.m4 to
affect all libraries (where we aren't sure the libraries are using
pkg_config to begin with).

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

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