[llvm-dev] *********How to get during compile time the base class of casted C++ object inside static_cast<> and dynamic_cast<> and the pointer of the casted object

[Paul via llvm-dev]

Hi Mehdi,

Ok. I see. I will keep this in mind and agree with your suggestions. I
will try to start a thread from the currently posted questions.

Regards
Paul

On 12/21/2016 05:43 PM, Mehdi Amini wrote:
>
>> On Dec 21, 2016, at 8:38 AM, Paul <paul at sec.in.tum.de
>> <mailto:paul at sec.in.tum.de>> wrote:
>>
>> Hi Mehdi,
>>
>> thanks a lot for your email. Actually I was disappointed by the fact
>> that I was not able to get a useful answer to my two questions.
>> As I observed that the questions move down along the list with time
>> passing I decided to re-post them in the hope that the questions
>> will have a better visibility.
>
> I don’t think we have a guideline on this, but reposting more than
> once a week seems too much.
>
>> Could you help me with the two questions? Finding an expert in this
>> area would be of great help. Do you think the questions are not well
>> stated.
>
> As mentioned in my previous email, you got two answers to your
> previous questions that went apparently ignored. A good starting point
> would be to iterate from there. Reposting the same question means that
> someone may spend time answering the same thing as the answer you
> already got because your repost does not maintain the threading /
> history of the discussion.
>
> — 
> Mehdi
>
>
>
>>
>> Regards
>>   Paul
>>
>> On 12/21/2016 05:31 PM, Mehdi Amini wrote:
>>> Hi Paul,
>>>
>>> It is the 4th time in two weeks that you repost the exact same two
>>> emails, that’s a bit high repost rate for the mailing-list,
>>> especially considering that you already got answers that you ignored
>>> previously:
>>>
>>> - http://lists.llvm.org/pipermail/llvm-dev/2016-December/108060.html
>>> - http://lists.llvm.org/pipermail/llvm-dev/2016-December/108051.html
>>>
>>> Adding an alternate email in case you didn’t receive previous emails.
>>> Best,
>>>
>>>
>>> — 
>>> Mehdi
>>>
>>>
>>>
>>>
>>>> On Dec 21, 2016, at 2:47 AM, Paul Muntean via llvm-dev
>>>> <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
>>>>
>>>> I want to detect bad casts in C++ code by using the Clang
>>>> compiler. The approach is similar to what Caver and TypeSan do but
>>>> without using the compiler-rt.
>>>>
>>>> Caver and TypeSan:
>>>> https://www.usenix.org/system/files/conference/usenixsecurity15/sec15-paper-lee.pdf
>>>> https://nebelwelt.net/publications/files/16CCS2.pdf
>>>>
>>>> For example if I have the following C++ code snippet where I want to
>>>> cast object b into
>>>> object D.
>>>>
>>>> D* obj = static_cast<D*>(b);
>>>>
>>>> from where (inside Clang, LTO, thinLTO, etc.) can I get the base class
>>>> of D and the base class ob b. Is this
>>>> available in the Clang compiler or LTO?
>>>>
>>>> Also, if b is an object of a virtual Class (class with inherited or its
>>>> own virtual functions) can I get its virtual pointer at compile time
>>>> by using the LTO?
>>>>
>>>> I found out that in CodeGen/CGExpr.cpp the explicit case
>>>> "BaseToDerived" is
>>>> handled and you can retrieve TypeSourceInfo using the function
>>>> getTypeInfoAsWritten(). It seems that this information is enough to get
>>>> the exact type of this cast at compile-time and should also work for
>>>> Template programming, as my, understanding is that Clang should have
>>>> abstracted the code into, specific types at this point.
>>>>
>>>> Am I wrong here?
>>>>
>>>> Is there any case where the type of the objects used inside the cast
>>>> not known at compile time? Can the,
>>>> 'real' type be hidden behind a pointer?
>>>> _______________________________________________
>>>> LLVM Developers mailing list
>>>> llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>
>>
>> -- 
>> Paul Muntean
>> Lehrstuhl für Sicherheit in der Informatik, I20
>> Prof. Dr. Claudia Eckert
>> Institut für Informatik TU-München
>> Boltzmannstr. 3, 85748 Garching, Germany
>> Tel.: ++49 (89) 289 - 18566
>> Fax : ++49 (89) 289 - 18579
>> Room: 01.08.055
>> E-Mail: paul at sec.in.tum.de 
>> https://www.sec.in.tum.de
>

-- 
Viele Grüße,
Paul Muntean
Lehrstuhl für Sicherheit in der Informatik, I20
Prof. Dr. Claudia Eckert
Institut für Informatik TU-München
Boltzmannstr. 3, 85748 Garching, Germany
Tel.: ++49 (89) 289 - 18566
Fax : ++49 (89) 289 - 18579
Room: 01.08.055
E-Mail: paul at sec.in.tum.de 
https://www.sec.in.tum.de

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