[lldb-dev] Call c/objc functions with the API

[Filipe Cabecinhas]

Hi,


On Fri, Feb 22, 2013 at 1:56 PM, Jim Ingham <jingham at apple.com> wrote:

>
> On Feb 22, 2013, at 1:51 PM, Enrico Granata <egranata at apple.com> wrote:
>
> >
> > Also, dealing with the arguments is going to be tricky.
> > Problems I can see at a glance:
> > - how do you deal with each SBValue while making the string? expression
> path? numeric value + a cast? neither way looks perfect at a glance
>
> I don't think you would make up a string.  You would implement this lower
> down than that, where we are directly populating the "arguments structure"
> that we are going to call, a la the Clang Functions.  And by the time we
> get there, we would have the method signature, so we'd know how to
> interpret the SBValues from the input arguments.
>
> Yes, bypassing the string building and just going for the clang AST or
something.


> > - for ObjC you need to also extract the “names of the arguments” (i.e.
> foo:arg1 bar:arg2 baz:arg3), while in C++ (arg1,arg2,arg3) is enough
>
> Again, you would be consing up a call to objc_msgSend with the arguments
> passed directly, so that would not be an issue.
>
> Jim
>
> I think you could even bypass objc_msgSend (though I don't know what it
does internally). You would get a reference to either a function, an ObjC
method that implements a selector (is my nomenclature right? :-P), or a C++
method, and then just creating something close to an llvm call instruction
(but going through clang first, to validate the call, perform any needed
conversions, and lower the arguments).

Regards,

  Filipe




>
> >
> > Of course, there are ways around these issues, but I am not sure this is
> useful enough to warrant the work required to get it right.
> >
> > The data formatters need a much more constrained subset of this
> functionality, so they implement their own wrapper.
> > Any special subset should be trivial to implement, the general case
> looks tricky.
> >
> > Enrico Granata
> > ✉ egranata@.com
> > ✆ 27683
> >
> > On Feb 22, 2013, at 12:14 PM, Jim Ingham <jingham at apple.com> wrote:
> >
> >> I'm not arguing for this, but you could do a fairly straightforward API
> like:
> >>
> >> SBValue
> >> SBValue::CallMethod(const char *methodName, SBValueList arguments);
> >>
> >> This would only work if the SBValue was a C++ or ObjC object.  In the
> ObjC case "methodName" would be the selector, and the value list would have
> to be in parameter order.
> >>
> >> I can see this being useful, though probably under the covers it would
> take some work to get it right...
> >>
> >> Jim
> >>
> >> On Feb 22, 2013, at 11:51 AM, Filipe Cabecinhas <
> filcab+lldb-dev at gmail.com> wrote:
> >>
> >>> I also don't think it should be in the SB layer. There's lots of stuff
> to deal with (arguments and their types, variable arguments
> selectors/functions, etc). I think creating an expression is better (maybe
> we can use clang so one doesn't have to generate an expression string?).
> >>>
> >>> Regards,
> >>>
> >>>  filipe
> >>>
> >>>
> >>> On Fri, Feb 22, 2013 at 10:23 AM, Enrico Granata <egranata at apple.com>
> wrote:
> >>> Currently, no.
> >>> You would have to craft your own expression and run it.
> >>>
> >>> The C++ data formatters have their own helper functions to do so. You
> can refer to lldb_private::formatters::ExtractValueFromObjCExpression for
> an example.
> >>>
> >>> I am not sure if this kind of API belongs in the SB layer. Ideas?
> >>>
> >>> Enrico Granata
> >>> ✉ egranata@.com
> >>> ✆ 27683
> >>>
> >>> On Feb 22, 2013, at 5:29 AM, Carlo Kok <ck at remobjects.com> wrote:
> >>>
> >>>> Does the api expose any way to execute an objc selector a given value
> (SBValue)?  (for example I have an NSException instance in an SBValue, and
> want to call "name" on it).
> >>>>
> >>>>
> >>>> What about global (c) functions?
> >>>>
> >>>>
> >>>> If not the api, how can I do the equivalent with the underlying api?
> >>>>
> >>>>
> >>>> Thanks,
> >>>> --
> >>>>
> >>>> Carlo Kok
> >>>>
> >>>>
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> >>>
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> >
>
>
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