为什么与 pthread 链接会导致分段错误? [英] Why does linking with pthread cause a segmentation fault?
问题描述
我有一个带有静态变量('abc.cpp')的简单程序:
I have a stripped down simple program with a static variable ('abc.cpp'):
#include <iostream>
int main(int, char**)
{
static const std::string a("123");
std::cout << "Hello world" << std::endl;
return 0;
}
我编译它并且它可以工作:
I compile it and it works:
> g++ -ggdb abc.cpp -o abc
> ./abc
Hello world
但是，如果我在 pthread 库中链接......
However, if I link in the pthread library....
> g++ -ggdb -lpthread abc.cpp -o abc
> ./abc
Segmentation fault (core dumped)
> gdb abc
(gdb) run
Starting program: abc
Program received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
(gdb) where
#0 0x0000000000000000 in ?? ()
#1 0x00007ffff7b01681 in ?? () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#2 0x00007ffff7b016c3 in std::locale::locale() () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#3 0x00007ffff7afe244 in std::ios_base::Init::Init() ()
from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#4 0x0000000000400d03 in __static_initialization_and_destruction_0 (__initialize_p=1,
__priority=65535) at /usr/include/c++/4.9/iostream:74
#5 0x0000000000400d2c in _GLOBAL__sub_I_main () at abc.cpp:8
#6 0x0000000000400d7d in __libc_csu_init ()
#7 0x00007ffff74a6e55 in __libc_start_main (main=0x400c06 <main(int, char**)>, argc=1,
argv=0x7fffffffdb58, init=0x400d30 <__libc_csu_init>, fini=<optimised out>,
rtld_fini=<optimised out>, stack_end=0x7fffffffdb48) at libc-start.c:246
#8 0x0000000000400b39 in _start ()
我知道它在这里不使用线程，但在实际的非精简程序中，它链接到一个使用线程的库.即使没有实际使用线程，也感觉应该可以链接到 pthread.
I know it doesn't use threading here, but in the actual non-stripped-down program, it links to a library that does use threading. It feels like it should be okay to link to pthread even though threading is not actually used.
有趣的是，添加消毒剂使其不会崩溃(不确定这是否是未定义"/不稳定的修复...).
Interestingly, adding the sanitizer makes it not crash (not sure if that's an "undefined"/unstable fix for it or not...).
> g++ -ggdb -fsanitize=undefined -lpthread abc.cpp -o abc
> ./abc
Hello world
为什么会导致段错误?
旁注:Clang 有效.
Side note: Clang works.
> clang++ -ggdb -lpthread abc.cpp -o abc
> ./abc
Hello world
版本信息:
> g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.9/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.9.2-0ubuntu1~14.04' --with-bugurl=file:///usr/share/doc/gcc-4.9/README.Bugs --enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.9 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.9 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --disable-vtable-verify --enable-plugin --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64 --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.9-amd64 --with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.9.2 (Ubuntu 4.9.2-0ubuntu1~14.04)
> dpkg -l 'libstdc++6*'
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-===================-==============-==============-===========================================
ii libstdc++6:amd64 5-20150329-1ub amd64 GNU Standard C++ Library v3
un libstdc++6-4.0-dbg <none> <none> (no description available)
un libstdc++6-4.1-dbg <none> <none> (no description available)
un libstdc++6-4.2-dbg <none> <none> (no description available)
un libstdc++6-4.3-dbg <none> <none> (no description available)
un libstdc++6-4.4-dbg <none> <none> (no description available)
un libstdc++6-4.5-dbg <none> <none> (no description available)
un libstdc++6-4.6-dbg <none> <none> (no description available)
un libstdc++6-4.7-dbg <none> <none> (no description available)
un libstdc++6-4.8-dbg <none> <none> (no description available)
ii libstdc++6-4.9-dbg: 4.9.2-0ubuntu1 amd64 GNU Standard C++ Library v3 (debugging file
un libstdc++6-5-dbg <none> <none> (no description available)
un libstdc++6-dbg <none> <none> (no description available)
这是用于 gcc 构建的 ldd abc:
Here's the ldd abc for gcc build:
linux-vdso.so.1 => (0x00007ffef8f2f000)
libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007f87b167c000)
libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f87b1465000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f87b109f000)
libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f87b0d99000)
/lib64/ld-linux-x86-64.so.2 (0x00007f87b1a11000)
还有 ldd abc 用于 clang 构建(注意这里的 pthread 而不是 gcc):
And the ldd abc for clang build (note the pthread here and not in gcc):
linux-vdso.so.1 => (0x00007fffa4cc7000)
libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fab1f10d000)
libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007fab1ed94000)
libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fab1ea8d000)
libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007fab1e876000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fab1e4b1000)
/lib64/ld-linux-x86-64.so.2 (0x00007fab1f347000)
对于它的价值，我的语言环境:
For what it's worth, my locale:
> locale
LANG=en_AU.UTF-8
LANGUAGE=en_AU:en
LC_CTYPE="en_AU.UTF-8"
LC_NUMERIC="en_AU.UTF-8"
LC_TIME="en_AU.UTF-8"
LC_COLLATE="en_AU.UTF-8"
LC_MONETARY="en_AU.UTF-8"
LC_MESSAGES="en_AU.UTF-8"
LC_PAPER="en_AU.UTF-8"
LC_NAME="en_AU.UTF-8"
LC_ADDRESS="en_AU.UTF-8"
LC_TELEPHONE="en_AU.UTF-8"
LC_MEASUREMENT="en_AU.UTF-8"
LC_IDENTIFICATION="en_AU.UTF-8"
LC_ALL=
设置默认语言环境会产生相同的结果(以及相同的堆栈跟踪):
Setting the default locale results in the same (and the same stack trace too):
> LC_ALL=C ./abc
Segmentation fault (core dumped)
推荐答案
原来是 GCC 编译器或 libstdc++ 出现错误/损坏.与 pthread 链接不应导致段错误.
It turns out it was the GCC compiler or libstdc++ that is buggy/broken. Linking with pthread shouldn't cause a segfault.
Clang 没有使用相同的 libstdc++ 的段错误，因此这表明它可能是编译器.我用 gcc 版本 5.1.0 (Ubuntu 5.1.0-0ubuntu11~14.04.1) 进行了测试，发现它有效，因此它确认了 GCC/libstdc++ 错误.
Clang didn't segfault, which is using the same libstdc++, so that suggests it may be the compiler. I tested with gcc version 5.1.0 (Ubuntu 5.1.0-0ubuntu11~14.04.1) and found it worked, so it confirms the GCC/libstdc++ bug.
使用的原始 GCC 4.9 来自非官方的测试编译器存储库(https://launchpad.net/~ubuntu-toolchain-r/+archive/ubuntu/test) - 不是官方的 Ubuntu 存储库.然而，经过测试的 GCC 5.1 也来自同一个存储库，因此至少在那里修复了错误.目前尚不清楚官方的 Ubuntu GCC 4.8 是否会导致此段错误.
The original GCC 4.9 which was used was from an unofficial test compiler repository (https://launchpad.net/~ubuntu-toolchain-r/+archive/ubuntu/test) - not the official Ubuntu repository. However the GCC 5.1 that was tested, was also from the same repository, so at least the bug was fixed there. It is not known as to whether the official Ubuntu GCC 4.8 causes this segfault or not.
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