zturner added inline comments.
================
Comment at:
lldb/trunk/source/Plugins/ScriptInterpreter/Python/PythonDataObjects.cpp:1075-1096
+static int readfn(void *ctx, char *buffer, int n)
+{
+ auto state = PyGILState_Ensure();
+ auto *file = (PyObject *) ctx;
+ int result = -1;
+ auto pybuffer = PyBuffer_FromMemory(buffer, n);
+ PyObject *pyresult = NULL;
----------------
lawrence_danna wrote:
> labath wrote:
> > zturner wrote:
> > > zturner wrote:
> > > > labath wrote:
> > > > > lawrence_danna wrote:
> > > > > > zturner wrote:
> > > > > > > I am still pretty unhappy about these functions, and passing
> > > > > > > function pointers into the `File` class.
> > > > > > >
> > > > > > > I think another approach would be this:
> > > > > > >
> > > > > > > 1) Make the `File` class contain a member
> > > > > > > `std::unique_ptr<IOObject> LowLevelIo;`
> > > > > > >
> > > > > > > 2) In `File.cpp`, define something called `class
> > > > > > > DefaultLowLevelIo : public IOObject` that implements the virtual
> > > > > > > methods against an fd.
> > > > > > >
> > > > > > > 3) In `PythonDataObjects`, define `PythonFileIo : public
> > > > > > > IOObject` and implement the virtual methods against a `PyObject`.
> > > > > > >
> > > > > > > 4) Add an additional constructor to `File` which takes a
> > > > > > > `std::unique_ptr<IOObject> LowLevelIo`, which we can use when
> > > > > > > creating one of these from a python file.
> > > > > > >
> > > > > > > One advantage of this method is that it allows the `PythonFileIo`
> > > > > > > class to be easily tested.
> > > > > > >
> > > > > > > (Also, sorry for not getting back to reviewing this several weeks
> > > > > > > ago)
> > > > > > I don't see how this approach gets around the problem that the
> > > > > > interfaces in SBDebugger use FILE *, not IOObject
> > > > > >
> > > > > > The only way I can see to do it the way you are saying is to also
> > > > > > add a SBIOObject, with swig wrappers to that, and variants of the
> > > > > > SBDebugger
> > > > > > interfaces that take IOObject instead of FILE *
> > > > > >
> > > > > > Do you want to do it that way?
> > > > > What's the final use case here. In the patch itself I don't see
> > > > > anything that would necessitate a FILE * conversion, but I don't know
> > > > > what do you actually intend to use this for. We can always return a
> > > > > null FILE * if the File object is backed by a a python file (we do
> > > > > the same for file descriptors, as there is no way to convert those
> > > > > into FILE*, not without going the fopencookie way).
> > > > Alright, I re-read this more closely. This is actually something I
> > > > wanted to fix for a long time. Specifically, I don't believe LLDB
> > > > should be using `FILE*` anywhere. I would prefer to mark this method
> > > > dangerous in big letters in the SB API, and add new versions that take
> > > > an fd. A `FILE*` doesn't even mean anything in Python. It's
> > > > specifically a native construct.
> > > >
> > > > I see it being used in two places currently. 1) Setting to `None`,
> > > > and 2) setting to the result of `open("/dev/null")`. The open method
> > > > documentation says "Open a file, returning an object of the file type
> > > > described in section File Objects".
> > > >
> > > > So when this method is being called from Python, it is not even a real
> > > > `FILE*`, it's a pointer to some python object. I think this is just a
> > > > bug in the design of the SB API, and we should fix it there.
> > > >
> > > > I don't often propose adding new SB APIs, but I think we need an
> > > > entirely different API here. There should be methods:
> > > >
> > > > ```
> > > > SetOutputFileHandle(SBFile F);
> > > > SetInputFileHandle(SBFile F);
> > > > SetErrorFileHandle(SBFile F);
> > > > ```
> > > >
> > > > And we should be passing those. This will in turn necessitate a lot of
> > > > trickle down changes in the native side too. We can mark the older
> > > > functions deprecated to indicate that people should no longer be using
> > > > them.
> > > >
> > > > Thoughts?
> > > Sorry, s/add a new version that takes an fd/add a new version that takes
> > > an SBFile/
> > >I don't often propose adding new SB APIs, but I think we need an entirely
> > >different API here. There should be methods:
> >
> > >SetOutputFileHandle(SBFile F);
> > >SetInputFileHandle(SBFile F);
> > >SetErrorFileHandle(SBFile F);
> > >And we should be passing those. This will in turn necessitate a lot of
> > >trickle down changes in the native side too. We can mark the older
> > >functions deprecated to indicate that people should no longer be using
> > >them.
> >
> > Note that these file handles eventually trickle down into libedit, which
> > expects to see a FILE *. These could probably be synthesized(*) for
> > libedit's usage alone, and leave the rest of the world oblivious to FILE*,
> > but it will need to be done very carefully.
> >
> > (*) Windows does not have a fopencookie/funopen equivalent afaik, but then
> > again, it also does not have libedit...
> > What's the final use case here
>
> LLDB integration with iPython. I want to be able to redirect LLDB's output
> to a python callback so I can interact with LLDB from inside an iPython
> notebook.
>
> > but I think we need an entirely different API here
>
> OK I will prepare a new version of the patch that introduces a SBFile API
Thanks, and apologies that the scope is kind of expanding here.
If possible, can you try to do this incrementally in several patches?
For example, a first pass you might just try having `SBFile` that wraps a
`lldb_private::File` and provides a couple of simple methods. This will allow
us to focus on the API bridge without having to worry about implementation
details.
Next add `SetOutputFile` etc, and try to update existing uses of
`SetOutputFileHandle` etc to use this new api. It should continue to work as
today, with the same bugs.
Then, implement the dynamic dispatch inside of `lldb_private::File` so that
python files and native files go to a different underlying implementation.
Repository:
rL LLVM
https://reviews.llvm.org/D38829
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