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

[Jean-Daniel Dupas]

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

> 
> -- Jean-Daniel
> 
> 
> 
> 
> 
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-- Jean-Daniel




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