[foreign] RFR 8220544: Jextract; library dependent header filtering

[Maurizio Cimadamore]

On 15/03/2019 18:01, Maurizio Cimadamore wrote:
>
> On 15/03/2019 17:48, Jorn Vernee wrote:
>> I've implemented this, and now doing a clean build based on the 
>> latest jdk/jdk merge before submitting the next webrev.
>>
>> It's working nicely, with one caveat; Some headers rely on 
>> pre-processor code defined in a parent header. For instance, Python.h 
>> defines some pre-processor code used in pythonrun.h . The example we 
>> have only uses functions defined in pythonrun.h, but if we just pass 
>> that header to jextract Clang throws an error because of the missing 
>> pre-processor code from Python.h
>>
>> In this case we have to pass Python.h first, and then pythonrun.h to 
>> get everything to work. This also relies on the existence of header 
>> include guards in the pythonrun.h header (since we're basically 
>> including it twice). A similar caveat exists with the Windows API.
>
> Doh! Maybe I've missed the simplest option after all.
>
> What if the root set was a 'first class' concept in the extraction 
> run, rather than something we infer from this or than command line 
> option?
>
> That way we could point jextract at python.h, but then say "hey, I'm 
> only really interested at stuff that comes from pythonrun.h".

In other words, right now we have

--include-symbol

and

--exclude-symbol

If not set, everything is included.

Maybe all we need is:

--include-header <header>

--exclude-header <header>

And, again, if none is specified, all headers are part of the 'root set'.

And, to address a concern you had - yes, I'd consider using the 'include 
path' for header names in --include/exclude-header

Maurizio

>
> Maurizio
>
>>
>> So, the guide-line is: Pass the main header first, then internal 
>> headers. e.g. If we have a main header A.h which includes a_impl.h, 
>> and another main header B.h which includes b_impl.h, headers should 
>> be passed to jextract in the order: A.h a_impl.h B.h b_impl.h
>>
>> I think the behavior being dependent on the ordering of the headers 
>> could be fixed by sorting the headers in topological order. But, 
>> there's still the requirement to pass all of them, or things break.
>>
>> Any thoughs about that?
>>
>> Thanks,
>> Jorn
>>
>>
>> Jorn Vernee schreef op 2019-03-15 14:40:
>>> I've already been using shell scripts mostly when running jextract
>>> (except for simple examples). I find it very useful to be able to
>>> split the command over multiple lines, especially long file paths
>>> become much more readable.
>>>
>>> I'll start working on this then.
>>>
>>> Jorn
>>>
>>> Maurizio Cimadamore schreef op 2019-03-15 14:21:
>>>> On 15/03/2019 13:15, Jorn Vernee wrote:
>>>>> I still like this approach, and I think adding support for 
>>>>> wildcard patterns and/or header filters would make it better.
>>>>>
>>>>> Like you said: It's dead simple. What you pass to jextract is what 
>>>>> you get. Though, we could still apply dependency analysis, which 
>>>>> would make sure nothing that's needed gets dropped.
>>>>
>>>> Why don't we try this then?
>>>>
>>>> Note that in javac we often use this trick:
>>>>
>>>> javac `find <path> -name *.java`
>>>>
>>>> which works
>>>>
>>>> also, note that jextract also accepts a file with the @ syntax, etc.
>>>>
>>>> jextract @args.txt
>>>>
>>>> where args.txt is the command line (which could list all the 
>>>> headers you want!).
>>>>
>>>> Maybe this is indeed the simpler approach.
>>>>
>>>> Maurizio