[cfe-dev] Semantic Analysis in Clang

Fri Jan 25 07:42:05 PST 2013

   Thanks a lot. I will report back any results. If you are interested, I
am using clang to write a provenance collection tool. Basically, clang is
used to rewrite a program such that it emits provenance information at
runtime. The literal meaning of provenance is "origin". The resulting code
after passing through my tool will report all function calls, their
arguments and return calls. It will be able to generate a complete runtime
control flow graph. This project is in collaboration with the Stanford
Research Institute and I will be very happy if you might consider making it
part of the clang extras (once it is done ).
   Any guidance on compiler theory would be much appreciated. Both my
supervising professors are experts in information theory and security so
it's up to me to figure all the things related to compilers.

Regards,
Adil

On Fri, Jan 25, 2013 at 8:30 PM, Manuel Klimek <klimek at google.com> wrote:

> On Fri, Jan 25, 2013 at 4:26 PM, Mohammad Adil <madil90 at gmail.com> wrote:
>
>> Hi,
>>   I am interested in helping any way I can. I am a research assistant and
>> always looking to help the community. Unfortunately, I am new to compiler
>> theory. If you can give me a few guidelines on how to achieve that, I would
>> be glad to help. Also, can you please name a few good resources on compiler
>> theory (my university isn't focusing on compilers so not many people here
>> to help).
>>
>
> +dgregor, who would be the right person to guide you here (or delegate
> said guidance to the right person).
>
>
>>     Regarding clang, what exactly happens when clang encounters an error
>> (I mean i want to pause the recursive visitor at the point when it
>> encounters an error and not end the program). Also, is it possible to
>>
>
> The RecursiveASTVisitor runs *after* clang finished parsing the program.
> Thus, I would think what you want to do is pretty much impossible.
>
>
>> parse the code in rewriter buffer without saving it (parse on the fly).
>>
>
> Yes, that's definitely possible. You can look at the examples in the c++11
> migration tool in the clang-extra-tools repository (
> http://llvm.org/viewvc/llvm-project/clang-tools-extra/trunk/cpp11-migrate/
> )
>
> Cheers,
> /Manuel
>
>
>>
>> Regards,
>> Adil
>>
>>
>> On Fri, Jan 25, 2013 at 7:52 PM, Manuel Klimek <klimek at google.com> wrote:
>>
>>> On Fri, Jan 25, 2013 at 3:43 PM, Mohammad Adil <madil90 at gmail.com>wrote:
>>>
>>>> Let us say that I write some code which has some errors. Now I am
>>>> reparsing it. Can I halt the parsing when I encounter an error so that I
>>>> can remedy it? If so, what happens to the AST? I mean, does it break at
>>>> that point or does it contain the rest of the code too with some kind
>>>> of substitution for the error part?
>>>>
>>>
>>> No, if you reparse it and it breaks, all you know is that what you
>>> wanted to do was incorrect... As I mentioned, whether this is a practical
>>> approach depends on what your fallback strategy is - for example, if you
>>> don't want to do anything in case of an error, simply not saving after
>>> getting an error in the reparsing would solve the problem.
>>>
>>> That said, it would be really cool to have full access to the lookup
>>> after the semantic analysis - so if you're interested in tackling this, I'd
>>> expect that you'd make a lot of people very happy :D
>>>
>>> Cheers,
>>> /Manuel
>>>
>>>
>>>>
>>>>
>>>>
>>>> On Fri, Jan 25, 2013 at 7:31 PM, Manuel Klimek <klimek at google.com>wrote:
>>>>
>>>>> On Fri, Jan 25, 2013 at 2:57 PM, Mohammad Adil <madil90 at gmail.com>wrote:
>>>>>
>>>>>> I need to insert some code in the file being parser. I need to make
>>>>>> sure that the resulting file compiles fine. The code that I am inserting
>>>>>> will mostly be " ostream << type_x ;". Now before I do that, I need to
>>>>>> ensure that "type_x" has a stream operator defined. Is that possible any
>>>>>> other way? I am very grateful for your help.
>>>>>>
>>>>>
>>>>> What we do in the c++11 transition tools in clang-extra is:
>>>>> - parse
>>>>> - detect place to insert
>>>>> - insert
>>>>> - reparse, look for errors
>>>>>
>>>>> Whether that's viable depends on how big the chance is that you're
>>>>> making an error, and what fallbacks you have.
>>>>>
>>>>> Cheers,
>>>>> /Manuel
>>>>>
>>>>>
>>>>>
>>>>>>
>>>>>> Regards,
>>>>>> Adil
>>>>>>
>>>>>>
>>>>>> On Fri, Jan 25, 2013 at 6:34 PM, Manuel Klimek <klimek at google.com>wrote:
>>>>>>
>>>>>>> On Fri, Jan 25, 2013 at 1:13 PM, Mohammad Adil <madil90 at gmail.com>wrote:
>>>>>>>
>>>>>>>> Thanks for the reply. Well, here's the detailed problem. Once all
>>>>>>>> the syntax checking has been done, the next step before generating IR is to
>>>>>>>> do semantic analysis and type checking. Let us say that I encounter a code
>>>>>>>> like this:
>>>>>>>>
>>>>>>>> string b;
>>>>>>>> vector<T> a;
>>>>>>>> cout<<b;
>>>>>>>> cout<<a;
>>>>>>>>
>>>>>>>>       How does clang figure out that the 3rd statement is valid
>>>>>>>> because an operator for string exists, while the 4rth statement is not
>>>>>>>> valid. More specifically, I want to know how clang searches through all the
>>>>>>>> operators (or functions). I have to use this functionality. Does the clang
>>>>>>>> api allow me to do this easily or will I have to replicate this
>>>>>>>> functionality?
>>>>>>>>
>>>>>>>
>>>>>>> As far as I know the clang API does not allow you to do that easily
>>>>>>> - you need the full semantic analysis state at that point during parsing,
>>>>>>> and as far as I'm aware this only exists implicitly in the Sema* classes.
>>>>>>> Overload resolution is one of those really complex and messy parts of C++ :)
>>>>>>>
>>>>>>> If you let us know what actual problem you're trying to solve, there
>>>>>>> might be solutions to that which are simpler than using overload resolution
>>>>>>> :)
>>>>>>>
>>>>>>> Cheers,
>>>>>>> /Manuel
>>>>>>>
>>>>>>>
>>>>>>>> Regards,
>>>>>>>> Adil
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> On Fri, Jan 25, 2013 at 4:35 PM, Manuel Klimek <klimek at google.com>wrote:
>>>>>>>>
>>>>>>>>> On Thu, Jan 24, 2013 at 12:49 PM, madil90 <madil90 at gmail.com>wrote:
>>>>>>>>>
>>>>>>>>>> Hi,
>>>>>>>>>>    I am looking to perform some semantic analysis in clang. More
>>>>>>>>>> specifically, I want to know whether a function exists for a
>>>>>>>>>> certain type.
>>>>>>>>>> The function is global. e.g.
>>>>>>>>>>
>>>>>>>>>> String toString(A a);
>>>>>>>>>>
>>>>>>>>>>     I want to differentiate that this function exists for type A
>>>>>>>>>> and not for
>>>>>>>>>> type B. I have built an AST and am parsing it. How can I achieve
>>>>>>>>>> this?
>>>>>>>>>> (Whenever I encounter a type)
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> I'd loop over all declarations of toString and see which type they
>>>>>>>>> take... Perhaps I'm misunderstanding your problem though :)
>>>>>>>>>
>>>>>>>>> Cheers,
>>>>>>>>> /Manuel
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>> Regards,
>>>>>>>>>> Adil
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> --
>>>>>>>>>> View this message in context:
>>>>>>>>>> http://clang-developers.42468.n3.nabble.com/Semantic-Analysis-in-Clang-tp4030012.html
>>>>>>>>>> Sent from the Clang Developers mailing list archive at Nabble.com.
>>>>>>>>>> _______________________________________________
>>>>>>>>>> cfe-dev mailing list
>>>>>>>>>> cfe-dev at cs.uiuc.edu
>>>>>>>>>> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> --
>>>>>>>> Mohammad Adil
>>>>>>>> LUMS SSE
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Mohammad Adil
>>>>>> LUMS SSE
>>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> Mohammad Adil
>>>> LUMS SSE
>>>>
>>>
>>>
>>
>>
>> --
>> Mohammad Adil
>> LUMS SSE
>>
>
>

-- 
Mohammad Adil
LUMS SSE
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