[CMake] parsing config.h files and setting cmake variables accordingly

[Clemens Arth]

Hi,

thanks for the hint, but my problem is exactly the opposite of the one 
configure_file is solving. I'm already using configure_file in multiple 
places, but here I don't want to write config files, instead I want to 
parse their content back to cmake, and that's why I don't think 
configure_file.

Regards
Clemens

Pau Garcia i Quiles wrote:
> Hello,
>
> Take a look at CONFIGURE_FILE
>
> On Fri, Feb 13, 2009 at 12:46 PM, Clemens Arth <clemens.arth at gmx.at> wrote:
>   
>> Hi,
>>
>> I've got a  question concerning  string processing in cmake. Our software
>> framework consists of multiple libraries and has many different features to
>> be enabled or disabled using #defines. For example, one option is to compile
>> with OpenGL or with OpenGL ES support. Thus in a config.h file, one of two
>> variables is valid to be #defined, USE_OPENGL or USE_OPENGLES. Depending on
>> the variable defined cmake should link against a specific set of libraries.
>>
>> Currently determining which feature is set works the following way in my
>> CMakeLists.txt:
>>
>> Code:
>> # check for the configuration and set the corresponding GL/GLES libraries
>> accordingly
>> FILE(READ ${LIB_SOURCE_DIR}/include/config.h CURRENT_CONFIG)
>> STRING(REGEX MATCH "\#define USE_OPENGLES" GLES_IS_SET ${CURRENT_CONFIG})
>> STRING(REGEX MATCH "\#define USE_OPENGL" GL_IS_SET ${CURRENT_CONFIG})
>> IF("#define USE_OPENGLES" STREQUAL "${GLES_IS_SET}")
>>   MESSAGE("GLES config!")
>> ELSE("#define USE_OPENGLES" STREQUAL "${GLES_IS_SET}")
>>   IF("#define USE_OPENGL" STREQUAL "${GL_IS_SET}")
>>       MESSAGE("GL config!")
>>   ELSE("#define USE_OPENGL" STREQUAL "${GL_IS_SET}")
>>       MESSAGE("Error! USE_GL or USE_GLES must be defined!")
>>   ENDIF("#define USE_OPENGL" STREQUAL "${GL_IS_SET}")
>> ENDIF("#define USE_OPENGLES" STREQUAL "${GLES_IS_SET}")
>>
>>
>> Note that this is really a bad hack. First, if GLES_IS_SET is set ,GL_IS_SET
>> is also set automatically. Second, if by accident the string does not
>> exactly match the content (an additional <space>, or there is a second
>> variable, for example called USE_OPENGL_EXTRAS), everything gets really
>> weird or fails at all. Finally, a problem is that cmake does not actually
>> notice if I changed the config.h file, so there should be an option to mark
>> the configuration as dirty if the config.h file is altered - this is a
>> problem which must not necessarily be solved, but maybe there is a simple
>> solution to this.
>>
>> Can someone give me some tips how to improve my really ugly solution?
>>
>> Thanks and best regards
>> Clemens
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>
>
>
>