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

[Jorn Vernee]

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.

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