[CMake] Touching files on cache var changes

[David Cole]

I do this by making a .in file that gets configured that contains the value
of the CMake variable.

header.h.in:
===========
#define FEATURE_X @FEATURE_X@

CMakeLists.txt:
===========
configure_file(${CMAKE_CURRENT_SOURCE_DIR}/header.h.in
  ${CMAKE_CURRENT_BINARY_DIR}/header.h
  @ONLY)
include_directories(${CMAKE_CURRENT_BINARY_DIR})

features.c:
===========
#include "header.h"

Now, when FEATURE_X changes in cmake, header.h changes, which triggers a
re-compile of any files that include it.


HTH,
David


On Tue, May 17, 2011 at 11:45 AM, Robert Bielik <robert.bielik at xponaut.se>wrote:

> Hi all,
>
> I'm wondering if there's a way to touch files on cached var changes. Let's
> say I have an option to enable or disable a feature
> in my application, and depending on its setting a preprocessor macro is
> defined (or not defined) in the CMakeLists.txt file:
>
> OPTION(FEATURE_X "Check to enable feature X" OFF)
>
> IF(FEATURE_X)
> ADD_DEFINITIONS(-DUSE_FEATURE_X=1)
> ELSE(FEATURE_X)
> ADD_DEFINITIONS(-DUSE_FEATURE_X=0)
> ENDIF(FEATURE_X)
>
> and in "features.c":
>
> ...
> #if USE_FEATURE_X
> // Code for feature X
>
> #endif
> ...
>
> The source code file "features.c" that have code depending on the
> preprocessor macro needs to be recompiled each time the option changes,
> which does not automatically
> happen if the macro is defined like above (and I _really_ need to have it
> defined, either to zero or one...).
>
> So I pretty much need to hook a dependency of "features.c" to change of
> cached cmake options/vars...
>
> Ideas?
> TIA
> /Rob
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