为什么在我启动新线程时 Valgrind 会出现段错误

Question

我正在用 C++ 编写程序，我注意到一些非常奇怪的事情。

当我运行我的程序在 Xcode 下时一切正常，但是当我在 Valgrind 下这样做时它会在几秒钟后给我一个 segmentation fault。

我设法提取了一个非常简单的代码，但它给出了错误：

#include <thread>

void exec_1() {}

int main(int argc, const char * argv[]) {

    std::thread simulator_thread;
    simulator_thread = std::thread(exec_1);
    simulator_thread.join();

    return 0;
}

我所做的只是使用这些标志在 Xcode 下构建我的可执行文件：

CFLAGS:

-I/usr/local/lib/python3.6/site-packages/numpy/core/include
-I/usr/local/Cellar/python3/3.6.1/Frameworks/Python.framework/Versions/3.6/include/python3.6m 
-Wno-unused-result -Wsign-compare -Wunreachable-code
-fno-common -dynamic -DNDEBUG -g -fwrapv -Wall -Wstrict-prototypes

LDFLAGS:

-L/usr/local/opt/python3/Frameworks/Python.framework/Versions/3.6/lib/python3.6/config-3.6m-darwin
-lpython3.6m -ldl -framework CoreFoundation

然后运行 Valgrind 下的可执行文件来查找内存泄漏。您会看到我正在调用 Python C API，因为我在我的 main 代码中使用了它，但是这段代码抛出了 segfault 而没有使用它们。

无论如何，Valgrind 以及其他一些东西会给我以下输出：

Thread 2:
==41660== Invalid read of size 4
==41660==    at 0x1016FA899: _pthread_body (in /usr/lib/system/libsystem_pthread.dylib)
==41660==    by 0x1016FA886: _pthread_start (in /usr/lib/system/libsystem_pthread.dylib)
==41660==    by 0x1016FA08C: thread_start (in /usr/lib/system/libsystem_pthread.dylib)
==41660==  Address 0x18 is not stack'd, malloc'd or (recently) free'd
==41660== 
==41660== 
==41660== Process terminating with default action of signal 11 (SIGSEGV)
==41660==  Access not within mapped region at address 0x18
==41660==    at 0x1016FA899: _pthread_body (in /usr/lib/system/libsystem_pthread.dylib)
==41660==    by 0x1016FA886: _pthread_start (in /usr/lib/system/libsystem_pthread.dylib)
==41660==    by 0x1016FA08C: thread_start (in /usr/lib/system/libsystem_pthread.dylib)
==41660==  If you believe this happened as a result of a stack
==41660==  overflow in your program's main thread (unlikely but
==41660==  possible), you can try to increase the size of the
==41660==  main thread stack using the --main-stacksize= flag.
==41660==  The main thread stack size used in this run was 8388608.
--41660:0:schedule VG_(sema_down): read returned -4

在 Valgrind 下生成线程是否可能是错误的原因？

P.S:
我的 OS 是 MacOS 10.12.5，我正在使用 Xcode 8.3.3 和 Valgrind 3.13.0。

Answer 1

Is it possible that spawning a thread under Valgrind is the cause of the error?

当运行使用 pthread 的二进制文件时，Mac OS X 上的 Valgrind 似乎确实存在问题：

访问不在 _pthread_find_thread 的映射区域内 (OS X 10.11) https://bugs.kde.org/show_bug.cgi?id=349128

您的 Valgrind 失败与此处报告的相似：

std::thread.join() SIGSEGV on Mac OS under Valgrind

Answer 2

我在使用 macOS 10.12.6 + Valgrind 3.13.0 时仍然面临同样的问题。

==82699== Process terminating with default action of signal 11 (SIGSEGV)
==82699==  Access not within mapped region at address 0x18
==82699==    at 0x10058E899: _pthread_body (in /usr/lib/system/libsystem_pthread.dylib)
==82699==    by 0x10058E886: _pthread_start (in /usr/lib/system/libsystem_pthread.dylib)
==82699==    by 0x10058E08C: thread_start (in /usr/lib/system/libsystem_pthread.dylib)
==82699==  If you believe this happened as a result of a stack
==82699==  overflow in your program's main thread (unlikely but
==82699==  possible), you can try to increase the size of the
==82699==  main thread stack using the --main-stacksize= flag.
==82699==  The main thread stack size used in this run was 8388608.
--82699:0:schedule VG_(sema_down): read returned -4
==82699== 
==82699== Events    : Ir
==82699== Collected : 30468496
==82699== 
==82699== I   refs:      30,468,496
Segmentation fault: 11

刚发现还有一个bug跟踪https://bugs.kde.org/show_bug.cgi?id=380269。这确实是一个历史错误。希望它不会再花 2 年才能修好。

为什么在我启动新线程时 Valgrind 会出现段错误

Why Valgrind segfaults when I launch a new thread

c++

multithreading

valgrind

segmentation-fault