[cfe-dev] Creating AStMatcher from code ?

[Manuel Klimek via cfe-dev]

On Mon, Mar 14, 2016 at 4:24 PM David Blaikie <dblaikie at gmail.com> wrote:

> On Mon, Mar 14, 2016 at 7:57 AM, mats petersson via cfe-dev <
> cfe-dev at lists.llvm.org> wrote:
>
>> Sorry about earlier message - premature "send"... :(
>>
>> So, surely this is rather hard to do.
>>
>> If you write match this: `class T; T* ptr = new T;`, what should it
>> match? Only the exact class called `T`? Or, the opposite extreme, any
>> assignment of new of any type, e.g "int *ptr = new int;"? What about "const
>> X* p = new Y;"? Or "std::vector<int*> a = { new int, new int }"?  What do
>> you want to do with `T* ptr{new T};` - it does essentially the same thing,
>> but syntactially and semantically, it's not identical - I'd expect the AST
>> is not identical - and if it is when you didn't want to match that, it's a
>> problem [although not solvable, since the AST is the same].
>>
>> Of course these examples are mostly nonsense and can be solved in other
>> ways, I'm just trying to point out that "matching something" often means
>> distinguishing "This is what I want to match, this I don't care about" -
>> so, do you care if the type is `const` or not, do you care if the type is a
>> `class` or `struct` vs. `int` etc? Do you care if it's exactly an
>> assignment, or anything that "kind of assigns".
>>
>> What I'm trying to say is that it would probably produce something to
>> start from, but I'm not convinced it is THAT much help, since you still
>> have to apply some fuzz and modify the code to do what you ACTUALLY want to
>> do.
>>
>
> One way to address this would be to allow multiple expressions and
> generate the most specific matcher that matches all those expressions.
> Still wouldn't catch all cases, but might help make the first pass a little
> closer to what you want.
>

And I have existence proof that this approach works well for simpler ASTs
(Java), but it's hard to say whether it would work equally well in C++


>
>
>>
>> --
>> Mats
>>
>> On 14 March 2016 at 14:48, mats petersson <mats at planetcatfish.com> wrote:
>>
>>> Sure
>>>
>>> On 14 March 2016 at 14:11, Manuel Klimek via cfe-dev <
>>> cfe-dev at lists.llvm.org> wrote:
>>>
>>>> On Mon, Mar 14, 2016 at 2:50 PM David Come via cfe-dev <
>>>> cfe-dev at lists.llvm.org> wrote:
>>>>
>>>>> Hello,
>>>>>
>>>>> I have been playing a bit with lib ASTMatcher and it is very tedious
>>>>> to use.
>>>>> My workflow is to dump the AST  for the relevant code and translate it
>>>>> into matchers, using clang-query to make sure it works.
>>>>>
>>>>> I was wandering is there was any tool (or proposal, work in
>>>>> progress...)
>>>>> for automating this work.
>>>>> The end goal would be give it some C++ code as input and have the
>>>>> corresponding matcher in output.
>>>>>
>>>>
>>>> Unfortunately there is no such tool. Would be awesome to have, though :)
>>>>
>>>>
>>>>>
>>>>> Thanks,
>>>>> David
>>>>> _______________________________________________
>>>>> cfe-dev mailing list
>>>>> cfe-dev at lists.llvm.org
>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>>>
>>>>
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>>>
>>
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