g ++无法解析stdlibc ++中使用的pthread_once [英] g++ doesn't resolve pthread_once used in stdlibc++

问题描述

我正在使用gtest，stdlibc ++和pthread静态链接程序，链接命令如下

I was static linking a program using gtest, stdlibc++ and pthread, the link command is as follows

g ++ -static -L/usr/local/lib -o测试run_test.o -lgtest -lstdc ++ -lgcc -lgcc_eh -lpthread -lc

g++ -static -L/usr/local/lib -o test run_test.o -lgtest -lstdc++ -lgcc -lgcc_eh -lpthread -lc

它可以生成二进制文件，但是每次我跟踪核心转储时都会崩溃

it can produce the binary but it crashes every time, when I trace the core dump

    #0  0x0000000000000000 in ?? ()
    #1  0x000000000048bf11 in __gthread_once (__func=0x48beb0 , 
        __once=)
        at /home/abuild/rpmbuild/BUILD/gcc-4.8.5/obj-x86_64-suse-linux/x86_64-suse-linux/libstdc++-v3/include/x86_64-suse-linux/bits/gthr-default.h:699
    #2  std::locale::_S_initialize () at ../../../../../libstdc++-v3/src/c++98/locale_init.cc:276
    #3  0x000000000048bf53 in std::locale::locale (this=0x7e3a98 )
        at ../../../../../libstdc++-v3/src/c++98/locale_init.cc:210
    #4  0x000000000045798c in basic_streambuf (this=)
        at /home/abuild/rpmbuild/BUILD/gcc-4.8.5/obj-x86_64-suse-linux/x86_64-suse-linux/libstdc++-v3/include/streambuf:466
    #5  stdio_sync_filebuf (__f=0x7dd580 , this=)
        at /home/abuild/rpmbuild/BUILD/gcc-4.8.5/obj-x86_64-suse-linux/x86_64-suse-linux/libstdc++-v3/include/ext/stdio_sync_filebuf.h:77
    #6  std::ios_base::Init::Init (this=) at ../../../../../libstdc++-v3/src/c++98/ios_init.cc:85
    #7  0x00000000004028fe in __static_initialization_and_destruction_0 (__initialize_p=1, __priority=65535)
        at /usr/include/c++/4.8/iostream:74
    #8  0x0000000000402927 in _GLOBAL__sub_I_main () at run_test.cpp:7
    #9  0x00000000004ac017 in __libc_csu_init (argc=argc@entry=1, argv=argv@entry=0x7ffcdf8db6d8, envp=0x7ffcdf8db6e8)
        at elf-init.c:88
    #10 0x00000000004ababd in __libc_start_main (main=0x4028ae , argc=1, argv=0x7ffcdf8db6d8, 
        init=0x4abfa0 , fini=0x4ac030 , rtld_fini=0x0, stack_end=0x7ffcdf8db6c8)
        at libc-start.c:244
    #11 0x00000000004027c7 in _start () at ../sysdeps/x86_64/start.S:122

并反汇编std :: locale :: __ S_initialize()中找到的二进制文件，而不是调用pthread_once的地址来生成生成的二进制callq 0.

and disassembled the binary found in std::locale::_S_initialize () the generated binary callq 0 instead of invoke the address of pthread_once.

      48bf0c:   e8 ef 40 b7 ff          callq  0 

使用objdump转储符号表并找到

used objdump to dump the symbol table and found

    0000000000000000  w      *UND*  0000000000000000 pthread_once
    0000000000000000  w      *UND*  0000000000000000 __pthread_once

它表明链接器知道pthread_once是未定义的弱符号，并拒绝对其进行解析.我必须添加链接器选项-Wl，-undefined = pthread_once，以强制链接器解析pthread_once以避免崩溃.

It shows that linker know pthread_once is undefined weak symbol and refuse to resolve it. I have to add linker option -Wl,--undefined=pthread_once to force linker to resolve pthread_once to avoid crash.

有人知道为什么链接程序无法解析pthread_once吗?

Does anyone know why linker doesn't resolve pthread_once ?

推荐答案

已将-Wl，-整个存档-lpthread -Wl，-否整个存档作为n.m进行了检查.提到，它有效.可以在 https://gcc.gnu.org中找到更多相关参考. /ml/gcc/2014-11/msg00246.html

Checked -Wl,--whole-archive -lpthread -Wl,--no-whole-archive as n.m. mentioned, it works. A more related reference can be found in https://gcc.gnu.org/ml/gcc/2014-11/msg00246.html

崩溃源于libstdc ++如何使用weakref属性在pthread之上实现称为gthread的包装器.总而言之，发生崩溃是因为

The crash comes from how libstdc++ uses weakref attribute to implement a wrapper called gthread on top of pthread. In summary, crash happens because

1. libstdc ++假定，如果定义了__pthread_key_create，则定义了pthread_once，而对于静态链接则不是这样.
在用户代码中的任何其他地方均未引用或定义
2. pthread_once.
3. gnu链接器无法解析未定义的弱符号pthread_once，没有链接错误，并且pthread_once的地址设置为0.
4. pthread_once被调用.

1. libstdc++ assumes that if __pthread_key_create is defined, then pthread_once is defined, while this is not true for static linking.
2. pthread_once is not referenced or defined any where else in user's code.
3. gnu linker doesn't resolve undefined weak symbol pthread_once, there is no link error and the address of pthread_once is set to 0.
4. pthread_once is called.

我同意--whole-archive link选项对于stdlibc ++和pthread的静态链接可能是最简单的解决方法.

I agree that --whole-archive link option might be the easiest work around for static linking of stdlibc++ and pthread.

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