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

[Clemens Arth]

Hi again,

now I have followed exactly that way and created a config.cmake file, 
which is translated into a config.h file. This approach works perfectly 
well on Linux and everything immediately responds to changes in the 
config.cmake file. However, if I create a Visual Studio project on 
Windows, the project itself gets updated according to changes in the 
config.cmake file, but the sources including config.h are not 
recompiled. Maybe I missed something, but even if the config.h file 
changes on a "build" command (and it really does!), the sources are all 
treated as up2date, so no rebuilding happens. Maybe there is a step 
missing, something like marking some files as dirty, but I don't really 
think so, or at least I can not imagine...

Clemens

Michael Jackson wrote:
> That is the best way to do it. Have all the options in your CMake file 
> and let the user select which options they want to compile with. Then 
> "configure_file" to create your config.h file.
>
>
> ---
> Mike Jackson                 www.bluequartz.net
>
>
>
> On Feb 13, 2009, at 7:45 AM, Clemens Arth wrote:
>
>> Hello,
>>
>> the config files were written some years ago simply to collect all 
>> the possibilities how to compile the projects. Unfortunately this was 
>> long before cmake came into play, thus the problem just came up now 
>> because I wanted to set up a system for nightly builds.
>>
>> Well, I think the best solution might be to drop the old config.h 
>> file and to replace it by a file for setting the variables in the 
>> cmake environment, and finally to create a new config.h version with 
>> cmake online with a call to configure_file. I think, this is, in 
>> principal, the way you might have kept in mind when you suggested a 
>> look at configure_file, right?
>>
>> Regards
>> Clemens
>>
>> Pau Garcia i Quiles wrote:
>>> Hello,
>>>
>>> I see. So, where is that config.h created? In your CMake build-system?
>>> is it from an external library? If the former, maybe you could use
>>> variables (cmake -DWITH_OPENGL:BOOL=1 ... ); if the latter, I don't
>>> know (the only thing I can come with at this moment to survive
>>> additional spaces, etc are regular expressions).
>>>
>>> On Fri, Feb 13, 2009 at 1:10 PM, Clemens Arth <clemens.arth at gmx.at> 
>>> wrote:
>>>
>>>> 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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>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>
>>>
>>>
>>>
>>
>> _______________________________________________
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>> Visit other Kitware open-source projects at 
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