[cfe-dev] Way to compare two Function bodies.

[Richard Smith]

On Wed, Jul 17, 2013 at 4:18 PM, Pavan Pattanada <pattanad at uci.edu> wrote:

> By "same", I mean, their ASTs to be the same to start with. I am working
> on a tool,  which is used to syntactic/semantic similarity between two
> versions of the code base. So far, I have been able to get the
> FunctionDecls of both versions of a function into memory. But I am not sure
> how to compare them.
>

This is still a little imprecise. Should functions compare equal if
variables have been renamed between them? What if an expression has been
rewritten into a trivially equivalent form (for instance, parentheses were
added or removed, or p->x was changed to (*p).x)?

Stmt::Profile does nearly what you want (it's the mechanism we use to
determine if two dependent expressions are equivalent for the purposes of
template redeclaration matching), but it will treat

  void f() { int n; }
  void g() { int n; }

as having different bodies, because they do not declare the same variable.
That's probably not very hard to fix.


> ~Pavan
>
>
> On Wed, Jul 17, 2013 at 3:42 PM, Richard Smith <richard at metafoo.co.uk>wrote:
>
>> On Wed, Jul 17, 2013 at 10:10 AM, Pavan Pattanada <pattanad at uci.edu>wrote:
>>
>>> Hi,
>>> I need to compare two versions of the same clang::FunctionDecl function
>>> body(a function in C). I would need to compare them statement by statement
>>> and say if the two versions are the same. Is there a neat way to do this in
>>> the clang framework?
>>>
>>
>> This question is too vague to answer: what do you mean by "the same"?
>> Same source text, same tokens, same tokens other than variable naming,
>> something else?
>>
>
>
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