Re: AC_SEARCH_LIBS directories on 32-bit and 64-bit

[Eric Blake]

On 10/18/2010 04:54 PM, Sergio Belkin wrote:
> Hi,
>
> Let's say we have the check:
>
> AC_SEARCH_LIBS([ns_get16],[resolv])
>
> How can I do to detect library directory path based on host
> architecture, I mean, I want that if is an x86_64 bit looks on
> ${prefix}/lib64 and if is 32-bit look on /usr/lib. I'd want to avoid
> that user has to provide manually LDFLAGS. Is that possible? If I am
> thinking something wrong, correct me.

Why should you want to offload the responsibility for the user setting 
up their system correctly in the first place?  And you can't blindly 
assume that ${prefix}/lib64 is the correct spelling, as there are 64-bit 
OSs that install their libraries directly in /usr/lib.  And, per the GNU 
Coding Standards, a user should feel free to install libraries in ~/lib 
(if they don't have write access to /usr) rather than /usr/local/lib 
(autoconf's default, good for installing optional packages above what 
the distro includes); as it is, libraries installed in /usr/lib64 is 
already a case of distros using the GCS-mandated ability to specify an 
alternate $prefix of /usr instead of the default /usr/local.

In my opinion, the solution to the 32- vs. 64-bit library question 
SHOULD be answered by the user (and not by the configure author). 
Obviously, this can be done by setting LDFLAGS for every configure run 
of every package, but that gets tiresome.  But more efficiently, this 
can be done by installing an appropriate config.site to answer the 
question up front.  And the manual already mentions how to do that:

http://www.gnu.org/software/autoconf/manual/autoconf.html#Site-Defaults

If a distro wants to ship 64-bit libraries in /usr/lib64, then they 
should also ship a config.site that automatically uses that directory 
any time a configure script targets ${prefix} of /usr, so that users 
automatically get this default without having to set LDFLAGS themselves. 
 But that's in the realm of the distro, not of autoconf.

As a package author, you shouldn't have to care about the distro's 
choice of spelling for preferred library location.

--
Eric Blake   address@hidden    +1-801-349-2682
Libvirt virtualization library http://libvirt.org