[cfe-dev] recent change broke -fcatch-undefined-behavior

[Jean-Daniel Dupas]

Le 16 oct. 2012 à 08:42, Alexey Samsonov <samsonov at google.com> a écrit :

> 
> 
> On Tue, Oct 16, 2012 at 1:46 AM, Jean-Daniel Dupas <devlists at shadowlab.org> wrote:
> 
> Le 15 oct. 2012 à 23:32, Jean-Daniel Dupas <devlists at shadowlab.org> a écrit :
> 
>> 
>> Le 15 oct. 2012 à 21:31, "Sean McBride" <sean at rogue-research.com> a écrit :
>> 
>>> On Mon, 15 Oct 2012 12:21:17 -0700, David Blaikie said:
>>> 
>>>>>>> I see that there have been recent changes wrt -fcatch-undefined-
>>>>>> behavior, and within the last week or so something changed such that my
>>>>>> own build of clang (built with CMake on OS X) is unable to build simple
>>>>>> programs that use -fcatch-undefined-behavior, I get link errors like:
>>>>>>> 
>>>>>>> "___ubsan_handle_divrem_overflow", referenced from:
>>>>>>>    _main in test-OSZvjm.o
>>>>>>> "___ubsan_handle_type_mismatch", referenced from:
>>>>>>>    _main in test-OSZvjm.o
>>>>>>> 
>>>>>>> Any ideas why?
>>>>>>> 
>>>>>> 
>>>>>> This is a new feature. Instead of generating traps, -fcatch-undefined-
>>>>>> behavior generates library calls that make it easier to find what is
>>>>>> wrong (each undefined behavior calls a different function).
>>>>>> 
>>>>>> This functions are provided by the ubsan library that is part of
>>>>>> compiler-rt. But I'm not sure the integration to the Makefile build
>>>>>> system is done yet.
>>>>> 
>>>>> You mean with the CMake build system?
>>>> 
>>>> Generally "Makefile build system" describes the configure+make build
>>>> system (at least when it's discussed here).
>>>> 
>>>>> Perhaps if I build using autotools it will work?  Or do you mean it
>>>> works nowhere yet?
>>>> 
>>>> I believe the implication is that it works with the CMake build
>>>> system. But you will need to checkout the compiler-rt LLVM project
>>>> into llvm/projects to build it along with clang. (& I assume you'll
>>>> need to install compiler-rt alongside clang as well, but hopefully the
>>>> install target does that)
>>> 
>>> As I said in my original post, I am using CMake (not autotools aka configure+make).  I do have llvm/projects.
>>> 
>>> My full little 'build everything' script is:
>>> 
>>> ------------
>>> (cd ~/llvm/llvm/; svn up)
>>> (cd ~/llvm/llvm/tools/clang; svn up)
>>> (cd ~/llvm/llvm/projects/compiler-rt; svn up)
>>> 
>>> mkdir -p ~/llvm/llvm-rel-bin
>>> rm -rf ~/llvm/llvm-rel-bin/*
>>> 
>>> mkdir -p ~/llvm/llvm-rel-install
>>> rm -rf ~/llvm/llvm-rel-install/*
>>> 
>>> cd ~/llvm/llvm-rel-bin
>>> CC="$(xcrun --find cc)" CXX="$(xcrun --find c++)" cmake -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_ASSERTIONS=OFF -DCMAKE_INSTALL_PREFIX=~/llvm/llvm-rel-install ../llvm
>>> make -j16 install
>> 
>> Yep, it looks like the driver integration for the darwin toolchain is missing too.
>> 
>> The ubsan library should probably be append to the link flags somewhere in Toolchains.cpp:DarwinClang::AddLinkRuntimeLibArgs(), but I don't see it anywhere.
>> 
> 
> Digging a little further, I found this in ubsan_value.h.
> 
> // For now, only support linux. Other platforms should be easy to add, and
> // probably work as-is.
> #if !defined(__linux__)
> #error "UBSan not supported for this platform!"
> #endif
> 
> Yes, as I can see ubsan runtime library is currently supported only in CMake build and is built on Linux only.

That's unfortunate that clang try to emit function calls on platforms that does not support it.

That said, do you need patches for darwin/make integration, or are you already working on it (or planning to do it after usban is done on linux) ? 

-- Jean-Daniel




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