[C++-sig] Py++ and caching

[Kirill Lapshin]

Hi Roman,

Is there a way to not regenerate source code if cache is valid? I.e. 
currently cache saves us from running gccxml, but the whole code 
generation phase is still carried out even though it does not really 
changes anything (unless there was a change in driver .py script).

Ideally I think what has to be done is: add an option to Py++ that will 
say these files are also a dependency (in addition to header(s) we are 
parsing with gccxml and the whole tree of headers #included from there); 
Py++ will run gccxml as before, only when needed, and will run code 
generation only if gccxml has been run or any additional dependencies 
have been modified since last time. We'll list driver script as 
additional dependency.

This will reduce runtime of Py++ to almost zero if no changes are needed.

I think I should be able to do something similar externally by tracking 
additional dependencies myself and asking cache prior to instantiating 
module builder. However I would imagine others may benefit from such 
functionality as well. Unless it already exists that is. :)

Best regards,

Kirill