[PATCH] D41215: Fix crash on invalid

[Rui Ueyama via llvm-commits]

I tried to test the behavior of BFD linker, and looks like the GNU linker
handles the symbol as a private one. The following program doesn't link
with the .so file.

  int _ZN8tcmalloc11ThreadCache17threadlocal_heap_E();
  int main() { return _ZN8tcmalloc11ThreadCache17threadlocal_heap_E(); }

When I change the function name (e.g. GetCdmVersion which is exported by
the .so), it worked. So I think I'm sure the GNU linker handles it as a
global symbol.

On Thu, Dec 14, 2017 at 1:48 PM, Peter Collingbourne <peter at pcc.me.uk>
wrote:

>
>
> On Thu, Dec 14, 2017 at 1:29 PM, Rui Ueyama <ruiu at google.com> wrote:
>
>> On Thu, Dec 14, 2017 at 1:22 PM, Peter Collingbourne <peter at pcc.me.uk>
>> wrote:
>>
>>> On Thu, Dec 14, 2017 at 10:27 AM, Rafael Avila de Espindola via
>>> llvm-commits <llvm-commits at lists.llvm.org> wrote:
>>>
>>>> Is libwidevinecdm.so available somewhere?
>>>>
>>>
>>> If you have a recent version of Chrome installed on your machine, you
>>> should be able to find a copy in your installation directory.
>>>
>>> We can try to make it a warning, but what is the correct thing to do
>>>> about _ZN8tcmalloc11ThreadCache17threadlocal_heap_E? Should we skip it?
>>>> Handle it as if it was global?
>>>>
>>>
>>> I think we should skip it. It looks like the symbol itself is supposed
>>> to be local.
>>> https://cs.chromium.org/chromium/src/third_party/tcmalloc/ve
>>> ndor/src/thread_cache.h?q=threadlocal_heap&sq=package:chromium&l=255
>>>
>>
>> Is it? It's a static member of some class and not a file local symbol.
>>
>
> Oh right, that wouldn't have caused the symbol to become STB_LOCAL then.
> It could have been made local as a result of the library being built with
> -fvisibility=hidden though. It could then have ended up in .dynsym as a
> result of one of the bugs mentioned here:
> https://sourceware.org/ml/binutils/2016-05/msg00076.html
>
> Peter
>
>>
>>
>>> Peter
>>>
>>>
>>>> Cheers,
>>>> Rafael
>>>>
>>>> Hans Wennborg via Phabricator <reviews at reviews.llvm.org> writes:
>>>>
>>>> > hans added a comment.
>>>> >
>>>> > This fixes the assert, now we error on it, which breaks our build all
>>>> the same. It's a pre-built .so, which I'm not sure exactly where it comes
>>>> from:
>>>> >
>>>> > FAILED: libwidevinecdmadapter.so
>>>> > ../../../../../../../../work/llvm/build.goma/bin/clang++ -shared
>>>> libwidevinecdm.so -Wl,--fatal-warnings -Wl,--build-id=sha1 -fPIC
>>>> -Wl,-z,noexecstack -Wl,-z,now -Wl,-z,relro -Wl,-z,defs -Wl,--no-as-needed
>>>> -lpthread -Wl,--as-needed -fuse-ld=lld -Wl,--icf=all -flto=thin
>>>> -Wl,--thinlto-jobs=8 -Wl,--thinlto-cache-dir=thinlto-cache
>>>> -Wl,--thinlto-cache-policy,cache_size=10\% -Wl,--lto-O0
>>>> -fwhole-program-vtables -m64 -Werror -Wl,-O1 -Wl,--gc-sections
>>>> -Wl,--gdb-index -nostdlib++ --sysroot=../../build/linux/debian_stretch_amd64-sysroot
>>>> -L../../build/linux/debian_stretch_amd64-sysroot/lib/x86_64-linux-gnu
>>>> -Wl,-rpath-link=../../build/linux/debian_stretch_amd64-sysroot/lib/x86_64-linux-gnu
>>>> -L../../build/linux/debian_stretch_amd64-sysroot/usr/lib/x86_64-linux-gnu
>>>> -Wl,-rpath-link=../../build/linux/debian_stretch_amd64-sysroot/usr/lib/x86_64-linux-gnu
>>>> -fsanitize=cfi-vcall -Wl,-rpath=\$ORIGIN/. -Wl,-rpath-link=. -o
>>>> "./libwidevinecdmadapter.so" -Wl,-soname="libwidevinecdmadapter.so"
>>>> @"./libwidevinecdmadapter.so.rsp"
>>>> > /usr/local/google/work/chromium/src/out/release/../../../../
>>>> ../../../../work/llvm/build.goma/bin/ld.lld: error: Found local symbol
>>>> '_ZN8tcmalloc11ThreadCache17threadlocal_heap_E' in global part of
>>>> symbol table in file libwidevinecdm.so
>>>> > clang-6.0: error: linker command failed with exit code 1 (use -v to
>>>> see invocation)
>>>> > ninja: build stopped: subcommand failed.
>>>> >
>>>> > Maybe the erorr could be downgraded to a warning? (We'd need to not
>>>> treat warnings as errors for this target on our side I suppose)
>>>> >
>>>> >
>>>> > https://reviews.llvm.org/D41215
>>>> _______________________________________________
>>>> llvm-commits mailing list
>>>> llvm-commits at lists.llvm.org
>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>>>>
>>>
>>>
>>>
>>> --
>>> --
>>> Peter
>>>
>>
>>
>
>
> --
> --
> Peter
>
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