[Qbs] dependency tracking

[Dan Pat]

>It's expected that the generator won't re-run, because the dependency
parsing happens when building a cpp file.
So, I guess, this explanation must be correct.

вт, 27 окт. 2020 г. в 15:22, Dan Pat <dannix84 at gmail.com>:

> >As Christian said: The problem is that the cpp scanner is triggered by the
> >generated cpp file, but there is no connection to the testinput.h because
> >your cpp files is not including it.
>
> Sorry for getting back to this so late. I have missed a very important
> detail - the generated cpp files do include the headers from which they are
> generated. To illustrate, I followed Richard's advice and prepended the cpp
> file with the line " #include "testinput.h" ". The modified Module
> definition (never mind the hardcoded string - it's just a test):
>
> Module {
>
>     id: testgen
>
>
>     Rule {
>
>         inputs: ["genxx"]
>
>         Artifact {
>
>             id: artifact
>
>             filePath: FileInfo.path(input.filePath)  + "/" + FileInfo.baseName(input.filePath) + "-gen.cpp"
>
>             fileTags: ["cpp"]
>
>         }
>
>         prepare: {
>
>
>             var cmd = new JavaScriptCommand();
>
>             cmd.description =  'Running test generator';
>
>             cmd.sourceCode = function(){
>
>                 var file = new TextFile(output.filePath, TextFile.WriteOnly);
>
>                 file.write("#include \"testinput.h\"\r\n const int c = 5;");
>
>                 file.close();
>
>
>             }
>
>
>             return cmd;
>
>
>         }
>
>     }
>
> }
>
>
> But the observed behavior is still the same.
>
>
> чт, 17 сент. 2020 г. в 04:25, Richard Weickelt <richard at weickelt.de>:
>
>> >> "testinput.h" file contains "#include "a.h" directive. Changing
>> >> testinput.h results in a generator run followed by a C++ compiler run.
>> >> Changing a.h results in no action, although in this case the generator
>> >> is intended to reprocess its input.
>> >
>> > It's expected that the generator won't re-run, because the dependency
>> > parsing happens when building a cpp file, i.e. all the headers are
>> > dependencies of the object file, and the header files themselves are
>> only
>> > "passed through" by the scanning process. Though you might be able to
>> > cheat by setting up a dummy cpp file that includes the top-level header
>> > and making that an input to the generator rule.
>>
>> As Christian said: The problem is that the cpp scanner is triggered by the
>> generated cpp file, but there is no connection to the testinput.h because
>> your cpp files is not including it.
>>
>> If you could add the following lines to your generated cpp file:
>>
>>     #ifdef IGNORED
>>     #include "testinput.h"
>>     #endif
>>
>> then this should be enough to make the cpp scanner think that you are
>> actually including testinput.h and hence, it will see and track a.h as
>> well.
>>
>> Richard
>> _______________________________________________
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>> Qbs at qt-project.org
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>>
>
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