[CMake] FindX11.cmake needs some work for 2.6.0

[Alan W. Irwin]

On 2008-04-14 15:56-0700 Alan W. Irwin wrote:

> Furthermore, making X11_LIBRARIES fullpath would benefit the PLplot build
> (and presumably other builds as well). When first setting up the CMake-based
> build system for PLplot, I either copied from our previous autotools-based
> build system or I may have noticed the potential for -l flags in
> X11_LIBRARIES.  But in any case, I prepended X11_LIBRARIES with
> "-L${X11_LIBRARY_DIR}" so that our users could have a non-standard install
> location for X (especially important for this era of frantic X development
> activity where some X testers may have multiple versions of X installed on
> their platform). However, this -L flag leads to CMP0003 warnings for the
> 2.6.0 release candidate since fullpath libraries are preferred for 2.6.x.
> (Also, X11_LIBRARY_DIR is an undocumented variable for FindX11.cmake which
> I would prefer not to depend upon in the long term.)

It turns out the X11_X_EXTRA_LIBS component of X11_LIBRARIES (the component
that potentially produces -l flags in FindX11.cmake) is determined by
multiple invocations of CHECK_LIBRARY_EXISTS with the third argument
(location) an empty string. Thus, X11_X_EXTRA_LIBS -l flags only correspond
to default system locations.  This means the "-L${X11_LIBRARY_DIR}" flag is
completely unneeded for PLplot so I will remove it.

It would be trivial to transform the -l flags in X11_X_EXTRA_LIBS to
fullpath names with the appropriate FIND_LIBRARY calls since only the system
default location needs to be searched.  However, now there is no motivation
for this change since the above "-L${X11_LIBRARY_DIR}" (or apparently any
other use of the internal X11_LIBRARY_DIR variable determined by
FindX11.cmake) is not needed.

Thus, it appears the present FindX11.cmake in 2.6.0-RC-8 is fine. My
apologies for taking so long to arrive at this conclusion.

Alan





The only remaining issue is replacing the -l flags in X11_X_EXTRA_LIBS with
full path names (which Bill has agreed is a worthwhile long-term
goal.
Furthermore, it also
should make it extremely easy to modify FindX11.cmake to replace the -l flags
with fullpath name libraries which Bill has agreed is a worthwhile long-term
goal.


>
> Of course, there are workaround for CMP0003 warnings, but the clean solution
> would be if a CMake developer would simply change FindX11.cmake in cmake cvs
> and also for 2.6.0 so that X11_X_EXTRA_LIBS and therefore X11_LIBRARIES are
> always consistently fullpath.  That would allow me to stop prepending
> "-L${X11_LIBRARY_DIR}" to X11_LIBRARIES which would eliminate the CMP0003
> warnings without compromising the need of some who require a non-standard
> install location for X.
>
> Alan
> __________________________
> Alan W. Irwin
>
> Astronomical research affiliation with Department of Physics and Astronomy,
> University of Victoria (astrowww.phys.uvic.ca).
>
> Programming affiliations with the FreeEOS equation-of-state implementation
> for stellar interiors (freeeos.sf.net); PLplot scientific plotting software
> package (plplot.org); the libLASi project (unifont.org/lasi); the Loads of
> Linux Links project (loll.sf.net); and the Linux Brochure Project
> (lbproject.sf.net).
> __________________________
>
> Linux-powered Science
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__________________________
Alan W. Irwin

Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).

Programming affiliations with the FreeEOS equation-of-state implementation
for stellar interiors (freeeos.sf.net); PLplot scientific plotting software
package (plplot.org); the libLASi project (unifont.org/lasi); the Loads of
Linux Links project (loll.sf.net); and the Linux Brochure Project
(lbproject.sf.net).
__________________________

Linux-powered Science
__________________________