[CMake] Generate *.cpp/*.hpp with add_custom_command, reference these in add_library in another subdirectory/CMakeLists?

[Martin Zenzes]

Hi,

I'm generating a *.cpp/*.hpp pair of files using add_custom_command() + 
add_custom_target(). These are then referenced in add_library() to be 
compiled and linked into a library, together with some "static" 
source-files. This works well as long as both parts (generating and 
creating the library) are in the same CMakeLists. This is also stated in 
the documentation [1]:

{{{
A target created in the same directory (CMakeLists.txt file) that 
specifies any output of the custom command as a source file is given a 
rule to generate the file using the command at build time.
}}}

My question: Is there a way to split the generating and compiling into 
different subdirectories/CMakeLists, and specify the "rule to generate 
the file" manually for the add_library() target?

The problem: At the time the add_library() is processed by cmake, the 
referenced *.cpp/*.hpp files are not yet created, hence they are not 
found ("Cannot find source file"). Adding the generate-target to ALL 
does not help, as at the target is executed to create the file _after_ 
the add_library() call is processed.

Any hints?

Greetings and thanks for your efforts.


[1] http://cmake.org/cmake/help/v2.8.7/cmake.html#command:add_custom_command