[CMake] acyclic builds 2.

[Egon Kocjan]

Hello,

I am trying to make cmake include file for libraries, so I can do for 
example:

add_executable(exea a.cpp)
include(../somelib/include.cmake)
use_somelib(exea)

exea will now have proper compile flags and target_link_libraries

(as you can see, I have used the approach with target_link_libraries as 
suggested in this email: 
http://www.cmake.org/pipermail/cmake/2008-April/020957.html)


The problem is writing use_somelib macro - cmake syntax is quite wordy. 
Remember that I have a large acyclic graph of dependencies and the same 
use_* macro may be called multiple times for the same target, also the 
same include file might be included multiple times. My painfully verbose 
solution, emulating C preprocessor techniques:

if(NOT somelib_include)
	set(somelib_include 1)

	... some general stuff ...

	macro(use_somelib TGT)
		if(NOT use_somelib_${TGT})
			set(use_somelib_${TGT} 1)

			if(NOT lib_somelib)
				set(lib_somelib 1)
				add_library(somelib ...)
			endif(NOT lib_somelib)

			target_link_libraries(${TGT} somelib)
			... add some cflags to TGT ...

		endif(NOT use_somelib_${TGT})
	endmacro(use_somelib TGT)
endif(NOT somelib_include)


Any suggestions on how to improve these patterns:

if(NOT x)
	set(x 1)
	...
endif(NOT x)

and

macro(y X)
	if(NOT y_${X})
		set(y_${X} 1)
		...
	endif(NOT y_${X})
endmacro(y)


Thanks
Egon Kocjan