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

Tue Feb 17 01:35:17 EST 2009

Yes, that was exactly what I did and it works on Linux, but it does not 
help in VS, unfortunately... VS sets up all the includes and linking 
options right, but then it prompts me to reload the project, and that's 
it....
only a complete "rebuild" lets the  project recompile the sources.

Clemens

Michael Jackson wrote:
> You would also want to add the configured file (config.h) to the list 
> of sources that get compiled.
>
> configure_file(...  config.h)
>
> add_executable(MyApp  main.c config.h)
>
> That way the dependency is setup between the configured file and the 
> compilation of the executable.
>
> Also I think it is generally better practice to have the input file 
> that is used in the configure_file command have the name "config.h.in" 
> rather than config.cmake. Having the .cmake file on the end may lead 
> to confusion when others look at your project.
>
> Cheers
> ---
> Mike Jackson                 www.bluequartz.net
>
>
>
> On Feb 16, 2009, at 5:32 AM, Clemens Arth wrote:
>
>> 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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>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>> _______________________________________________
>>>> Powered by www.kitware.com
>>>>
>>>> Visit other Kitware open-source projects at 
>>>> http://www.kitware.com/opensource/opensource.html
>>>>
>>>> Please keep messages on-topic and check the CMake FAQ at: 
>>>> http://www.cmake.org/Wiki/CMake_FAQ
>>>>
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>>>
>>> _______________________________________________
>>> Powered by www.kitware.com
>>>
>>> Visit other Kitware open-source projects at 
>>> http://www.kitware.com/opensource/opensource.html
>>>
>>> Please keep messages on-topic and check the CMake FAQ at: 
>>> http://www.cmake.org/Wiki/CMake_FAQ
>>>
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>>
>