[CMake] cmake for cygwin

[Alan W. Irwin]

On 2010-10-26 17:53-0400 Bill Hoffman wrote:

> The policy mechanism might not be ideal but in a year or so, all of this 
> would go away, and the meantime the patches you have to maintain for cygwin 
> ports would become trivial.  The patch would basically have a set cmake 
> version at the top.   I thought the command line option was a nice 
> compromise.

Bill, as somebody associated with a software package (PLplot) which
already works on Cygwin, I think the policy mechanism is the ideal way
to handle this requested change.  I do believe the Cygwin packagers
when they say the change will make a lot more projects build without
issues on Cygwin, but it is also extremely likely their preferred
solution (breaking backwards compatibility for cmake) would also break
currently working builds (such as the PLplot one) on Cygwin.

I sympathize with the frustrations of the Cygwin packagers at the
slowness with which this issue has been dealt with, but OTOH, I am not
sure they completely understand the neat resolution of the issue that
you are now offering with a policy-based approach to the requested
change. Thus, I suggest you just go ahead and implement that preferred
solution without further frustrating delays. Then publish cookbook
instructions about the one-line change that needs to be made in the
top-level CMakeLists.txt file of each currently non-working Cygwin
project (but not the working ones like PLplot) in order for the new
policy to be recognized. Ideally, upstream projects that currently
don't build on Cygwin will adopt this solution, but if they are slow
in doing that, it should not be too difficult for the Cygwin packagers
to implement a sed (or whatever) script to do the required one-line
changes in the top-level CMakeLists.txt files for each package in an
automatic fashion.

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).
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Linux-powered Science
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