[LLVMdev] C sequence-point analyzer

[Chad Rosier]

Hi Lukas,
I don't fully understand what you're working on, but you might consider
looking at how the -fcatch-undefined-behavior flag is implemented as a
starting point.  This flag enables various run-time checks for undefined
behavior.

I would also email the cfe-dev list as I'm guessing this is something
you'll want to implement on the clang side.

You might also consider looking at these:
http://clang.llvm.org/docs/index.html (Specifically, the Sanitizers) and
http://clang.llvm.org/docs/DataFlowSanitizer.html

Hope this helps,

 Chad


> Hi all,
>
> I'm trying to write a tool for detecting undefined behavior in C
> regarding sequence points and side effects.
>
> I'm not sure whether it should be a Clang plugin or LLVM run or
> something completely different (I'm really new to both Clang and LLVM)
> and that's what I need advice with.
>
> For my work, I need to use both AST and alias analysis
>
> Clang plugin:
> 	+relatively easy to use
> 	+access to AST with all the needed info EXCEPT alias analysis (right?)
> 	-no alias analysis, I'd need to write one myself
>
> LLVM run:
> 	+built-in alias analysis (I'd like to use it, writing my own alias
> analysis is not really what my work is all about)
> 	-I do NOT have access to AST
> 	-I don't know it at all (but I'm ready to learn it if it shows up to be
> the best option)
>
> The big PROBLEM is: a behavior that is undefined in C (and which Clang
> has access to) might be (and in my case WILL be) well defined in LLVM
> (for example, i=i++; is undefined in C but in LLVM code it will be
> already well defined and the result will depend on Clang behavior).
>
> So I thought I could use both, in Clang create a list of rules, for
> example "On line L, there is an undefined behavior if X aliases with Y"
> and then SOMEHOW dig this info from LLVM run.
>
> Is this a good idea? Is there a way (other than output to file from
> Clang and then read it in LLVM) to give this set of rules to LLVM? I'd
> also be glad for any other idea, not necessarily including LLVM and
> Clang, to solve this problem.
>
> Thanks in advance!
>
> --
> *****************************
> Lukas Hellebrandt
> kamikazecz at gmail.com
> *****************************
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> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
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>


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