[CMake] how to add capability to generate preprocessed and not-yet-compiled files ?

[Brad King]

John Ellson wrote:
> Brad King wrote:
>> Alexander Neundorf wrote:
>>> Hi,
>>>
>>> it would be nice if it would be possible to have for each object file 
>>> also a target which only preprocesses the file and one which 
>>> preprocesses and compiles, but not assembles the file (so that you 
>>> get the assembler code).
>>>
>>> Is there a way to do this with macros ? I almost think this would 
>>> have to be done in cmake itself. Probably somewhere where the object 
>>> rules are created additionally for each object the same rule but with 
>>> "-E" instead of "-c" would have to be created. It wouldn't be 
>>> required to be executed on all, just on direct invocation:
>>> make foo.o/pre
>>> make foo.o/as
>>>
>>>
>>> What do you think about this ?
>>> Would you accept a patch ?
>>
>> Look in Modules/CMakeCInformation.cmake for the variable 
>> CMAKE_C_COMPILE_OBJECT.  Other modules in the Platform directory set 
>> it also.  Just duplicate the variable with one called 
>> CMAKE_C_PREPROCESS_OBJECT and then setup 
>> cmLocalUnixMakefileGenerator3.cxx to create rules with ".E" extensions 
>> instead of ".o".  You should be able to locate places that lookup 
>> *_COMPILE_OBJECT vars.  See Modules/CMakeCXXInformation.cmake for the 
>> C++ version.
> 
> Not sure that I'm following the converstation properly here, but
> can any of this be used to provide access to a set of .o for use as a 
> "convenience library" ?

No, these variables are used to specify rules for the generators to put 
in the build files.

-Brad