[erlang-questions] Multiple dialyzer PLTs?

[Tobias Lindahl]

Michael Radford wrote:
> Kostis Sagonas writes:
>> Michael Radford wrote:
>>> I'm wondering how difficult (or even possible) it would be for dialyzer
>>> to support either reading multiple PLT files at startup, or a way to
>>> merge multiple PLT files that were produced separately.
>> Reading multiple PLT files at startup and merging the information in 
>> them is possible, but the end result is not as good as you would expect 
>> it to be whenever there are dependencies between functions in the 
>> different PLTs.  To do a good job one needs to essentially re-analyze 
>> the code of these functions/modules.
> 
> That's pretty much what I figured; but even an incomplete analysis that
> included other libraries would be an improvement over our current
> situation where we ignore them.
> 
> Of course I understand that from a correctness standpoint, it would be
> even better to analyze the entire codebase together.  But with many
> libraries that are constantly being upgraded, I don't think it will fly
> to require all the developers to wait for dialyzer to run after every
> package installation.
> 
> Could you offer any pointers on where to start if I were to try to
> implement reading multiple PLT files?

Most of the ptl handling is done in dialyzer_plt.erl and it interacts 
with dialyzer_cl.erl in order to find out what needs to be reanalyzed. 
You might also want to have a look at dialyzer_succ_typings.erl and its 
interaction with dialyzer_contract.erl, but start out with the first two 
modules.

It shouldn't be too hard to make this happen, at least as long as the 
plts are non-overlapping, or when the overlapping information is 
identical (e.g., the plts was built from the same otp-plt). The main 
reason we haven't done this is that it is the points Kostis made about 
the information.

Happy hacking!

Tobias

> 
> Thanks for your help (and for a great tool),
> 
> Mike
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