[RFC] Using duchain in QMake support

David Nolden zwabel at googlemail.com
Sat Mar 8 11:42:49 UTC 2008

On Saturday 08 March 2008 10:19:08 Andreas Pakulat wrote:
> - Is "Foo = Bar\n...\nFoo = A B C" only a definition or also a use of
>   the Variable Foo? i.e. Foo is re-defined to a different value.
That depends on how you interpret it. After all it's you who builds the 
uses/declarations specifically for the language, in the way that you think it 
makes sense.

However I'd say that the first assignment is a declaration, because "Foo" 
isn't declared yet, and the second assignment contains a use of the 
declaration of "Foo".

> - Can I find the last occurence of a variable assignment within a
>   certain context?
Sure, as long as you record each assignment as a use. However a use doesn't 
contain additional information like the actual expression that is being 

> - qmake supports config scopes, i.e. "win32 { ... } unix { ...}"
>   can I map that with the environment stuff? How do I later on access
>   all the different config-parts (so I can enable a switch in the ui
>   "show files from all platform-configs")
I don't think you will need such complicated stuff like the C++ environment 
management, but I also don't know how this exactly works within QMake, so I 
cannot answer it clearly.

> - I guess the include-file stuff in C++ still works properly when having
>   a #include in the middle of the file right? (In qmake its not uncommon
>   to do a include(somefile.pri) in the middle of a file, especially with
>   the config scopes)
Yep in C++ that works. In general, it should be nothing more than a simple 

> - Does expression evaluation in C++ support function calls? I guess not,
>   but I probably need this for QMake. Is it feasible to calculate this
>   during duchain building, or should I just note a use of the function
>   and later on calculate it "on the fly"?

In C++, usually only the return-types of functions are evaluated, because 
that's all that can be represented statically. Static expressions like "const 
int a = otherInt + 5" or "SomeClass<otherConstInt + 5>" are also evaluated 
wherever needed, either while building the duchain, or later.

Probably it'll be fine for you to evaluate the functions while building the 

Greetings, David

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