[CMake] multiple targets depending on generated file

[Clinton Stimpson]

I'm looking at bug #11884
http://public.kitware.com/Bug/view.php?id=11884

And I've noticed there is a problem with depending on generated headers across 
directories but not within the same directory.

For example:

# section A
add_custom_command(OUTPUT ${CMAKE_BINARY_DIR}/out.h  COMMAND ....)
add_executable(... ${CMAKE_BINARY_DIR}/out.h ...)

# section B
add_custom_command(OUTPUT out2.h COMMAND .. DEPENDS ${CMAKE_BINARY_DIR}/out.h)
add_executable(... out2.h ...)


If section A and B are in the same CMakeLists.txt, then there is no problem.

If they are in sibling directories, then building section B first will lead to 
an error about out.h missing.  A workaround involves the user of 
add_dependencies() and/or a custom target.

Is this a bug in CMake?  It seems there is enough information given that CMake 
could notice the dependency.  But maybe it can't quite do it because its a 
separate directory?  Maybe cmake can do the add_dependencies() automatically?

-- 
Clinton Stimpson
Elemental Technologies, Inc
Computational Simulation Software, LLC
www.csimsoft.com