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<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen">Howdy,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen">I’m looking to add a dependency to all source files to ensure that a generated file is up-to-date before compilation. This generated file is “passed in” to the compiler via a global compiler
definition. Is there an easy or built-in way to do this, or will I need to manually add a made-up target to every file in every library directory?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen">Currently, the generated file is created in the CMake Options file, using an exec_program command near the top of the file. The output of this process is not tracked, but the GLOBAL_DEFS
variable applied to every source file includes a line that directs the compiler to consume the new file. It looks a little like this:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen">Lib_options.cmake<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen">[…]<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen">exec_program(<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"> <executable><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"> ARGS <o:p>
</o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"> -o <outputFile><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"> -I <inputFile><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"> -x <extraArgs…><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen">)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen">[…]<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen">set (GLOBAL_DEFS<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"> -D<definitions…><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"> -@<outputFile><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen">)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen">[…]<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen">However, the dependency tree is not aware of this file and will not prepare it in any way on a per-file bases. In this case the program is executed every build regardless of if <inputFile>
has been modified. This adds unnecessary time to an incremental build if no change is made, and if <inputFile> does happen to change CMake will not recompile the sources accordingly. I have to do a clean/rebuild in order for the changes to “take”.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen">What I would like to see is a way to actually add <outputFile> as a dependency to each source file. Now, I’m no CMake expert, but I think it would look something like this:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen">Lib_options.cmake<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen">[…]<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"># Create a command/target for our output file<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen">add_custom_command(<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"> OUTPUT<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"> <outputFile><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"> DEPENDS<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"> <inputFile><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"> COMMAND<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"> <executable><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"> ARGS<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"> -o <outputFile><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"> -I <inputFile><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"> -x <extraArgs…><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen">)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"># Do something to make all source files depend on <outputFile><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"># <Magic goes here><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen">[…]<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen">set (GLOBAL_DEFS<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"> -D<definitions…><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"> -@<outputFile><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen">)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen">[…]<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen">Would this be a feasible thing to do in CMake, especially at the options file level? If you need any more information please let me know.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:Consolas;color:darkgreen">Thank you in advance!<o:p></o:p></span></p>
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