[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

[Mehdi Amini via llvm-dev]

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> 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?
> _______________________________________________
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> llvm-dev at lists.llvm.org
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