CMake policy settings with CMake 2.8.8

[Alexander Neundorf]

Hi,

I was just looking through the cmake policies which were added after 2.6.4, 
and what to do with them.

These are the following:
CMP0010: Bad variable reference syntax is an error (already in 2.6.3)
CMP0012: if() recognizes numbers and boolean constants
CMP0013: Duplicate binary directories are not allowed
CMP0014: Input directories must have CMakeLists.txt.
CMP0015: link_directories() treats paths relative to the source dir.
CMP0016: target_link_libraries() reports error if only argument is not a 
target.
CMP0017: Prefer files from the CMake module directory when including from 
there.

Actually, all of them sound reasonable, but in kdelibs we have to guarantee 
source compatiblity, so we cannot simply enable (set them to NEW) them, 
because this might break the build of existing projects.

CMP0017 is already set to NEW, mostly because of us (and our version of 
FindPackageHandleStandardArgs.cmake in kdelibs/cmake/modules/).


Beside this one, I'm thinking about setting the following to NEW:

CMP0010: this makes cmake abort if it finds a cmake syntax error. This is a 
good thing. I don't think there can be projects out there which have this 
problem and which nevertheless build.


CMP0013: According to the docs, in 2.6.4 duplicate binary directories were an 
error, but since 2.8.0 it's a warning by default. I think this should be an 
error.


All others I think we should keep at OLD.

While CMP0016 is good candidate, this problem may exist in some projects, but 
it doesn't actually cause any errors. So probably better keep it silent 
instead of breaking the build.

CMP0012 is dangerous, since it could break builds, and if a developer then 
makes his application build again, it may not build with an older kdelibs 
anymore.


Comments ?


Alex