[CMake] Sharing objects between executables - solved

[pellegrini]

thanks for your help Alexander & Michael.

Eric



Michael Hertling a écrit :
> On 10/04/2011 10:42 AM, pellegrini wrote:
>   
>> Hi all,
>>
>> I would need your advise about the strategy to adopt when two 
>> executables share common object files.
>>     
>
> Sharing object files among different targets might mean asking for
> trouble - possibly quite subtle trouble - since different targets'
> object files may need to be compiled with different sets of flags,
> defines etc.; in particular, think of -fPIC w.r.t. object files
> destined for a static library as well as for a shared one.
>
>   
>> Here is the context. I have a project that consists in a program (e.g. 
>> console_prog) that was historically a console program
>> on top of which a GUI (gui_prog) was built. The gui_prog calling 
>> directly the console program via an input file generated by the GUI.
>>
>> As the gui by itself does not mean anything without its console partner, 
>> I built a CMakeLists.tx file that contains two add_executables:
>>
>>     - add_executable(console_prog console_prog.f90 module1.f90 
>> module2.f90 module3.f90 ...)
>>     - add_executable(gui_prog gui_prog.f90 module1.f90  module2.f90)
>>
>> My problem is that gui_prog uses some routines included in the source 
>> files of the console program (e.g. module1.f90 module2.f90).
>> I would like to avoid a double build of module1.f90, module2.f90
>>
>> I see two possibilities:
>>     - building a static libraries out of the common files and linking it 
>> to both console_prog and gui_prog executables
>>     
>
> Unless you have very good reasons to not do so, this is definitely what
> you should aim at. Besides, that's the basic idea of object libraries.
>
>   
>>     - using the set_source_files_properties command on the objects files 
>> generated by pfind build with GENERATED option set to true.
>>
>> Which approach do you think suit the best to my purpose ? If this is the 
>> second one: is there an easy way to get/specify the list of the
>> object files generated during the pfind build ?
>>     
>
> You might use a RULE_LAUNCH_COMPILE target property for this purpose:
>
> # CMakeLists.txt:
> CMAKE_MINIMUM_REQUIRED(VERSION 2.8 FATAL_ERROR)
> PROJECT(LOF C)
> SET(CMAKE_VERBOSE_MAKEFILE ON)
> FILE(WRITE ${CMAKE_BINARY_DIR}/main.c "int main(void){return 0;}\n")
> ADD_EXECUTABLE(main1 main.c)
> SET_TARGET_PROPERTIES(main1 PROPERTIES RULE_LAUNCH_COMPILE "sh
> ${CMAKE_SOURCE_DIR}/lof.sh <OBJECT> ${CMAKE_BINARY_DIR}/\$\$(basename
> <SOURCE>).o")
> SET_SOURCE_FILES_PROPERTIES(${CMAKE_BINARY_DIR}/main.c.o PROPERTIES
> GENERATED TRUE)
> ADD_EXECUTABLE(main2 ${CMAKE_BINARY_DIR}/main.c.o)
> SET_TARGET_PROPERTIES(main2 PROPERTIES LINKER_LANGUAGE C)
>
> # lof.sh:
> ln -s "$1" "$2"; shift 2; exec "$@"
>
> However, this approach is limited to Makefile generators and makes use
> of platform-specific tools like basename, so it's usually inadvisable.
>
> Regards,
>
> Michael
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-- 
Eric Pellegrini
Calcul Scientifique
Institut Laue-Langevin
Grenoble, France