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

[Michael Jackson]

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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>>>>> Please keep messages on-topic and check the CMake FAQ at:
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>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>
>>
>>
>>
>>
>
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