[cfe-dev] Creating AStMatcher from code ?

[David Blaikie via cfe-dev]

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.


>
> --
> 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
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>>>>
>>>
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>>
>
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