[cfe-dev] Sanitizer test failures when switching to libc++ by default

[Hahnfeld, Jonas via cfe-dev]

From: Alexey Samsonov [mailto:vonosmas at gmail.com] 
Sent: Friday, February 05, 2016 11:05 PM
To: Kostya Serebryany
Cc: Hahnfeld, Jonas; cfe-dev at lists.llvm.org
Subject: Re: [cfe-dev] Sanitizer test failures when switching to libc++ by default

 

On Fri, Feb 5, 2016 at 11:11 AM, Kostya Serebryany via cfe-dev <cfe-dev at lists.llvm.org> wrote:

 

 

On Fri, Feb 5, 2016 at 6:21 AM, Hahnfeld, Jonas via cfe-dev <cfe-dev at lists.llvm.org> wrote:

Hi all,

I'm currently looking into (optionally) switching the default C++ stdlib to
libc++ (see http://reviews.llvm.org/D15920 which hasn't received a review so
far)
I've resolved all regression test failures in clang which are now passing
cleanly.

I'm now investigating the failing sanitizer tests in compiler-rt, here's
what I got so far:
 - two tests use -static-libstdc++ which obviously needs a -stdlib=libstdc++
(asan/TestCases/throw_invoke_test.cc and tsan/static_init6.cc)

 

Makes sense. 

I wonder if we can also use -static-libc++ for these tests

 

At least in my build there is not static version of libc++… I think this isn’t built by default but I haven’t yet searched for an opt-in.

 

 - tsan builds an instrumented version of libc++ and adds their headers.
This leads to errors with default C headers which are #include_next'd in
libc++. These #include_next then find the headers of the "normal" libc++
which in turn instantly return because of the header guards. Therefore basic
functions like printf aren't defined.
Solution: Pass -nostdinc++ to disable the headers of the "normal" libc++

 

emm, probably. 

 

Just to clarify: do you want to pass it to TSan lit tests? How would you ensure that

we'll still pick up C++ standard library headers when tests are run with Clang configured

to use libstdc++?

 

I’m planning on passing it in test/tsan/lit.cfg around line 57. Those flags are only applied if an instrumented version of libcxx is available and there is an explicit definition of the header include path, so this should work.

 

 

 - lsan completely fails with libc++, I had to generally pass
-stdlib=libstdc++ - is this known and possibly still work in progress?

 

This is not known to me. What are the symptoms? 

 

“LeakSanitizer has encountered a fatal error” on all C++ tests. This is fixed when building the tests with “-stdlib=libstdc++”, everything else still built with libc++…

I also can’t debug with gdb because the errors seems to not occur inside a debugger :-( is there any special trick with the sanitizers inside a debugger that I have not found yet? 

 


Greetings,
Jonas

--
Jonas Hahnfeld, MATSE-Auszubildender

IT Center
Group: High Performance Computing
Division: Computational Science and Engineering
RWTH Aachen University
Seffenter Weg 23
D 52074  Aachen (Germany)
Hahnfeld at itc.rwth-aachen.de
www.itc.rwth-aachen.de


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-- 

Alexey Samsonov
vonosmas at gmail.com

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