ThreadSanitizer SEGFAULT

[jbayardo]

I wrote the following code:

#include <iostream>
#include <thread>
#include <atomic>
#include <functional>
#include <chrono>

void dekker(std::atomic<int> &x, std::atomic<int> &y, std::atomic<int> &r) {
    std::this_thread::sleep_for(std::chrono::milliseconds(5));
    x.store(1, std::memory_order_release);
    r.store(y.load(std::memory_order_acquire), std::memory_order_relaxed);
}

int main() {
    std::atomic<int> x, y, r1, r2;
    while (true) {
        x = y = r1 = r2 = 0;

        std::thread t1(dekker, std::ref(x), std::ref(y), std::ref(r1));
        std::thread t2(dekker, std::ref(y), std::ref(x), std::ref(r2));
        t2.join();
        t1.join();

        if (r1.load() == 0 && r2.load() == 0) {
            std::cout << "ERROR! Found forbidden condition." << std::endl;
            exit(-1);
        }
    }

    return 0;
}

When compiling with clang++ -fsanitize=thread --std=c++11 -lpthread file.cc and running, I get the following:

FATAL: ThreadSanitizer CHECK failed: /build/buildd/llvm-toolchain-3.4-3.4/projects/compiler-rt/lib/sanitizer_common/sanitizer_linux.cc:462 "((IsOneOf(*current_, 's', 'p'))) != (0)" (0x0, 0x0)
[1] 24515 segmentation fault (core dumped) ./a.out

This is using Ubuntu 14.04.5 LTS (Trusty Tahr) and:

» clang++ --version
Ubuntu clang version 3.4-1ubuntu3 (tags/RELEASE_34/final) (based on LLVM 3.4)
Target: x86_64-pc-linux-gnu
Thread model: posix

[dvyukov]

Does this reproduce with a newer clang? 3.4 is more than 3 years old, lots of bugs was fixed since then.

[jbayardo]

Still happens when installing it from the official repos:

clang version 6.0.0-svn310059-1~exp1 (trunk)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/bin

Gives out the following:

FATAL: ThreadSanitizer CHECK failed: /build/llvm-toolchain-snapshot-6.0~svn310059/projects/compiler-rt/lib/sanitizer_common/sanitizer_procmaps_linux.cc:47 "((IsOneOf(current_, 's', 'p'))) != (0)" (0x0, 0x0)
#0 __tsan::TsanCheckFailed(char const, int, char const*, unsigned long long, unsigned long long) ??:? (a.out+0x48bb9f)
#1 __sanitizer::CheckFailed(char const*, int, char const*, unsigned long long, unsigned long long) ??:? (a.out+0x4a7385)
#2 __sanitizer::MemoryMappingLayout::Next(__sanitizer::MemoryMappedSegment*) ??:? (a.out+0x4a3139)
#3 __tsan::CheckAndProtect() ??:? (a.out+0x492ada)
#4 __tsan::InitializePlatform() ??:? (a.out+0x4925d4)
#5 __tsan::Initialize(__tsan::ThreadState*) ??:? (a.out+0x48036c)
#6 _dl_init /build/eglibc-SvCtMH/eglibc-2.19/elf/dl-init.c:111 (discriminator 2) (ld-linux-x86-64.so.2+0x10429)
#7 (ld-linux-x86-64.so.2+0x1299)

[dvyukov]

Need to understand what's different in your environment. It generally works for other people.

What version of linux do you use? uname -a output?
Does it happen with int main(){} program?
Does -fsanitize=address work?

[jbayardo]

I'm sorry, I just realized I was running this under a Windows Subsystem for Linux environment by mistake; it seems to have strange effects on how memory is allocated and so on. I'm closing this issue. Thanks!