[cfe-dev] Source to source transformation w/ comments

[David Blaikie via cfe-dev]

On Fri, May 6, 2016 at 1:25 PM, Andre Vehreschild <vehre at gmx.de> wrote:

> Well, how is this supposed to guide me on the right way? I mean even when
> I stick to the Ast when transforming, the comments aren't in there one way
> or the other.
>

I think there might be a mode/flag/setting for parsing comments that's not
on by default for performance reasons.


> And given that we are transforming to Java it will get somewhat difficult
> to store the transformed program in the existing Ast structures, cause they
> aren't made for Java. So what are you proposing, David?
>

The intention isn't to change the AST, but to use the AST to figure out how
to change the source (eg: get the source location from the AST, then insert
text at the right location, etc)

If the transformation is sufficiently invasive, like changing languages,
that approach might not be feasible - in which case you'll be in some
pretty untested territory & I'm not sure of the right direction.

- Dave


>
> Regards,
> Andre
>
>
> Am 6. Mai 2016 19:19:38 MESZ, schrieb David Blaikie <dblaikie at gmail.com>:
>>
>> Generally roundtripping through ASTs is not something that's
>> encouraged/reliable for reasons such as this. Most tools doing source
>> transformations do so by editing the original code, rather than producing a
>> new derived piece of code.
>>
>> On Fri, May 6, 2016 at 7:31 AM, Andre Vehreschild via cfe-dev <
>> cfe-dev at lists.llvm.org> wrote:
>>
>>> Hi all,
>>>
>>> I am working on a project to rework a given program having a large code
>>> base. While using Clang's fine and elaborate ways to understand and
>>> massage an AST, I am missing a way to parse and transfer comments. I
>>> have seen some efforts so far to get doxygen comments for methods and
>>> so on. But what about the comments that document the working of
>>> functions, i.e., all the comment that are in the .cpp files?
>>>
>>> Is there any support on this?
>>>
>>> What would be a good way to get them transfered? A new AST node on
>>> stmt-level to refer to a comment in the SourceManager, i.e., quite light
>>> weight? Or are there other loose ends that I can attach to?
>>>
>>> Because I am constructing the transformed code in a bottom-up way
>>> (bottom being the leaves of the AST), and am just streaming the result
>>> into a stringstream, I can't traverse the resulting code a second time
>>> and inject the comments while looking for source locations.
>>>
>>> Furthermore would it be appreciated to have a way of control on the
>>> transformation process, i.e. tell the clang-tool that for a certain
>>> routine it should do something specific. I.e. a directive should be
>>> available. Any thoughts on this?
>>>
>>> I am willing to develop and provide patches to get that functionality,
>>> but for this I like know a design that would be well perceived and has
>>> chances to make it into clang, i.e., not to waste the effort.
>>>
>>> - Andre
>>> --
>>> Andre Vehreschild * Email: vehre ad gmx dot de
>>> _______________________________________________
>>> cfe-dev mailing list
>>> cfe-dev at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>
>>
>>
> --
> Andre Vehreschild
>
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