[CMake] Out of source dependencies.

[Schwartz, Philip]

I have come up with a partial solution to this issue by putting the add_subdirectory into a macro that is called to do the add along with the add_depend.

It looks for a variable of ${CMAKE_PROJECT_NAME}_BUILT in order to determine if it should add_subdirectory or just add_depend.

The issue now is that I recieve warnings of overiding commands and ignoring old commands for the shared dependency.

Let me clarify my earlier post.

My top level project contains 4 projects.

/trunk/a   (Only Executable)
/trunk/b
/trunk/c
/trunk/d

To Build, a requires b.  b requires c.  Both a and c require d.

In a:
project(a)
set(BASEDIR /trunk)

add_subdirectory(${BASEDIR}/b ${CMAKE_BINARY_DIR}/b)
add_subdirectory(${BASEDIR}/d ${CMAKE_BINARY_DIR}/d)
...

In b:
project(a)
set(BASEDIR /trunk)

add_subdirectory(${BASEDIR}/c ${CMAKE_BINARY_DIR}/c)
...

In c:
project(a)
set(BASEDIR /trunk)

add_subdirectory(${BASEDIR}/d ${CMAKE_BINARY_DIR}/d)
...

This method fails due to the same Bin dir being used for d in both c and a.

To solve this, I created a macro that does the following along with adding set (${CMAKE_PROJECT_NAME}_BUILT 1) to all projects

if(${_name}_BUILT)
    add_dependencies(${_target} ${_name})
else()
    add_subdirectory(${_src} ${_bin})
    add_dependencies(${_target} ${_name})
endif()

The issue that now appears is that project d has the following warnings when make is ran.
CMakeFiles/Makefile2:76051: warning: overriding commands for target `trunk/d/CMakeFiles/d.dir/all'
CMakeFiles/Makefile2:64065: warning: ignoring old commands for target `trunk/d/CMakeFiles/d.dir/all'
CMakeFiles/Makefile2:76063: warning: overriding commands for target `trunk/d/CMakeFiles/d.dir/rule'
CMakeFiles/Makefile2:64077: warning: ignoring old commands for target `trunk/d/CMakeFiles/d.dir/rule'
CMakeFiles/Makefile2:76074: warning: overriding commands for target `trunk/d/CMakeFiles/d.dir/clean'
CMakeFiles/Makefile2:64088: warning: ignoring old commands for target `trunk/d/CMakeFiles/d.dir/clean'

What would cause this issue in the makefiles?



________________________________
From: cmake-bounces at cmake.org [mailto:cmake-bounces at cmake.org] On Behalf Of Schwartz, Philip
Sent: Monday, January 25, 2010 4:33 PM
To: cmake at cmake.org
Subject: [CMake] Out of source dependencies.

The current project that I am working on has multiple projects layered through subdirectories. The project was a conversion from traditional makefiles and when we do a cmake build from the root of the source tree all is done correctly. The issue comes to when we try and build a single component from a out of source build directory (we are requiring out of source builds).

I have found a temp solution for example

/trunk/a
/trunk/b
/trunk/c


a requires b and b requires c to build correctly. As long as they dont share dependencies, if I use add_subdirectory(src ${CMAKE_BINARY_DIR}/<project>) for each it works to build the deps as needed. The issue is if both a and c require the another dep pulled in the same way. The error that comes up is through a policy error of CMP0013.

Yes, I could disable the policy, but would prefer a more elegant solution for the issue. Any help would be appreciated.

--Philip

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