[cfe-dev] Non-PIC code causes ld --shared to fail when using -fsanitize=undefined in trunk but not 3.4.

[Alexey Samsonov]

This should be fixed by r212064. Sorry for delay, and thanks for the report!


On Wed, May 7, 2014 at 12:42 PM, Reid Kleckner <rnk at google.com> wrote:

> Thanks for the report!
>
> I am not a sanitizer expert, but here's what I think is happening.
>
> The ubsan runtime is linked statically into all DSOs in the user's
> program, but the other sanitizer runtimes are only linked statically into
> the main executable.  Because the other sanitizers are only present in the
> main executable, they can use a more efficient TLS access model.  It looks
> like some of this TLS leaked into the common sanitizer runtime code, and
> got linked into the ubsan runtime, which doesn't work.
>
>
> On Fri, May 2, 2014 at 5:04 AM, Prof Brian Ripley <ripley at stats.ox.ac.uk>
> wrote:
>
>> It is not clear to me which list covers use of this flag, but as it
>> appears to this user as a compiler bug, I am posting here.  Please tell me
>> where is the correct place if this is not it.
>>
>> We use clang to run UBSAN over code for the R project, which makes
>> extensive use of DSOs to dynamically load extensions.  This works fine with
>> 3.4, but not with the trunk.
>>
>> For an empty file test.c, trunk gives
>>
>> clang -fsanitize=undefined -fpic -g -O2 -mtune=native -c test.c -o test.o
>> clang -fsanitize=undefined -shared -o test.so test.o
>> /usr/bin/ld: /usr/local/clang3.5t/bin/../lib/clang/3.5.0/lib/linux/
>> libclang_rt.san-x86_64.a(sanitizer_tls_get_addr.o): relocation
>> R_X86_64_TPOFF32 against `_ZN11__sanitizerL4dtlsE' can not be used when
>> making a shared object; recompile with -fPIC
>> /usr/local/clang3.5t/bin/../lib/clang/3.5.0/lib/linux/
>> libclang_rt.san-x86_64.a(sanitizer_tls_get_addr.o): could not read
>> symbols: Bad value
>> clang: error: linker command failed with exit code 1 (use -v to see
>> invocation)
>>
>> whereas 3.4 successfully compiled test.so.
>>
>> This is x86_64 Linux, specifically Fedora 20, and trunk compiled starting
>> with clang 3.4. I first saw this around early Feb 2014, and some bisection
>> shows that r200062 was the last version I tried that worked.
>>
>> --
>> Brian D. Ripley,                  ripley at stats.ox.ac.uk
>> Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
>> University of Oxford,             Tel:  +44 1865 272861 (self)
>> 1 South Parks Road,                     +44 1865 272866 (PA)
>> Oxford OX1 3TG, UK                Fax:  +44 1865 272595
>> _______________________________________________
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>> cfe-dev at cs.uiuc.edu
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>>
>
>
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>


-- 
Alexey Samsonov, Mountain View, CA
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