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List:       cfe-commits
Subject:    Re: [libcxx] r243574 - Recommit r243503 "[libcxx] Cleanup CMake configuration and integrate with LLV
From:       Eric Fiselier <eric () efcs ! ca>
Date:       2015-07-30 2:58:28
Message-ID: CAB=TDAX6ppuLDhpx4Bp4rZQuZKKnoM5cGk+or0GTut9wtrpS0A () mail ! gmail ! com
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> Eric, what part of your change caused this behavior change? Probably, after you've \
> started to execute LLVM CMake modules, you've modified link flags used to build \
> shared objects, and now they are required to have no unresolved symbols?

This is exactly what is happening. HandleLLVMOptions.cmake adds
"-Wl,-z,defs" on linux when LLVM_USE_SANITIZER is not specified.
We also pick up -ffunction-sections and -fdata-sections. What effect
do those have on building with sanitizers?


One of the main reasons for this patch was to make it easier for
libc++ to support sanitizer configurations.
I would like the libc++ build to support each sanitizer configuration.
Currently it seems like compiler-rt is better at
building libc++ with sanitizers than libc++ is.

Would anybody be willing to help with:
A) Figuring out the proper flags for building and linking libc++ with
each sanitizer.
B) Moving some of the compiler-rt CMake logic for building libc++ into
libc++ if applicable.

/Eric

On Wed, Jul 29, 2015 at 8:54 PM, Alexey Samsonov <vonosmas@gmail.com> wrote:
> I've submitted r243599 that slightly improves things: now libcxx can be
> configured with "Clang+TSan", but the build fails with a bunch of
> "undefined reference to `__tsan_read8'"
> errors when we are trying to link libc++.so.
> 
> Generally, we *don't* link in TSan runtime into shared objects - it should
> only be linked into the executable, and __tsan_* symbols should be
> left unresolved. Eric, what part of your change caused this behavior change?
> Probably, after you've started to execute LLVM CMake modules,
> you've modified link flags used to build shared objects, and now they are
> required to have no unresolved symbols?
> 
> On Wed, Jul 29, 2015 at 5:21 PM, Alexey Samsonov <vonosmas@gmail.com> wrote:
> > 
> > I think I've found the "problem", causing CMake identification of Clang
> > version. I will submit it shortly.
> > 
> > On Wed, Jul 29, 2015 at 4:50 PM, Kostya Serebryany <kcc@google.com> wrote:
> > > 
> > > Thanks, check-msan works for me again.
> > > 
> > > 
> > > 
> > > On Wed, Jul 29, 2015 at 4:47 PM, Eric Fiselier <eric@efcs.ca> wrote:
> > > > 
> > > > Reverted as r243593.
> > 
> > 
> > 
> > 
> > --
> > Alexey Samsonov
> > vonosmas@gmail.com
> 
> 
> 
> 
> --
> Alexey Samsonov
> vonosmas@gmail.com
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