[CMake] How to query compiler definitions?

[SF Markus Elfring]

> set_source_files_properties(debug_funcs.c PROPERTIES
>    EXCLUDE_FROM_CONFIGURATIONS "Release;MinSizeRel")

I do not want to exclude this file based on the value of the variable 
"CMAKE_BUILD_TYPE".   ;-)


> I don't think it would make to do this based on preprocessor definitions.

It seems that our ideas converge.   :-)


> So, toy.cxx is not actually the problem,

Correct.


> but you don't want to link against the XML library.

Partly. yes.

I am affected by a general issue from C++ class libraries. The corresponding 
free source files were copied to a subdirectory of the project I am interested 
in because a public shared library (*.so/*.dll) seems to be missing for it. (The 
project has got its own bundle of external software.)

Library features are used in a limited way so far. This has got the consequence 
that its compilation should be optional for specific application parts.


> Do you need the library anyways (e.g. for other targets) [...] ?

The software test part depends on the C++ class library unconditionally.


> However, if libxml is required for debugging only and you don't want to
> require it unconditionally, you have a problem and I can't see an easy
> way around it.

The utility "http://grinninglizard.com/tinyxml/index.html" is needed in my case.

Regards,
Markus