【发布时间】：2018-02-20 23:49:36
【问题描述】：
当我尝试编译以下程序时
#include <iostream>
#include <memory>
#include <thread>
#include <vector>
// This function will be called from a thread
void call_from_thread()
{
std::cout << "Threaded: Hello, World" << std::endl;
}
int main()
{
std::cout << "Hello World" << std::endl;
std::thread t1(call_from_thread);
t1.join();
std::cout << "Goodbye World" << std::endl;
}
通过这个电话
pi@raspberrypi:/tmp $ arm-linux-gnueabihf-g++ -g -Wall -O0 -ggdb -Wl,-z,nocopyreloc segfault_check.cpp -o segv_test -lpthread
它将在没有警告的情况下编译。在这种情况下，目标机器是运行 rapbian stretch 和 gcc 6.3.0 的 raspberry 计算模块 3。尝试运行它会在到达主入口点之前立即导致段错误。
GNU gdb (Raspbian 7.12-6) 7.12.0.20161007-git
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Reading symbols from segv_test...done.
(gdb) run
Starting program: /tmp/segv_test
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/arm-linux-gnueabihf/libthread_db.so.1".
Program received signal SIGSEGV, Segmentation fault.
0x00000000 in ?? ()
(gdb) bt
#0 0x00000000 in ?? ()
#1 0x76e99148 in __dynamic_cast () from /usr/lib/arm-linux-gnueabihf/libstdc++.so.6
#2 0x76f105f4 in bool std::has_facet<std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > > >(std::locale const&) () from /usr/lib/arm-linux-gnueabihf/libstdc++.so.6
#3 0x76f02f94 in std::basic_ios<char, std::char_traits<char> >::_M_cache_locale(std::locale const&) () from /usr/lib/arm-linux-gnueabihf/libstdc++.so.6
#4 0x76f030c0 in std::basic_ios<char, std::char_traits<char> >::init(std::basic_streambuf<char, std::char_traits<char> >*) () from /usr/lib/arm-linux-gnueabihf/libstdc++.so.6
#5 0x76eab684 in std::ios_base::Init::Init() () from /usr/lib/arm-linux-gnueabihf/libstdc++.so.6
#6 0x00010de8 in __static_initialization_and_destruction_0 (__initialize_p=1, __priority=65535) at /usr/include/c++/6/iostream:74
#7 0x00010e28 in _GLOBAL__sub_I__Z16call_from_threadv () at segfault_check.cpp:44
#8 0x00011db4 in __libc_csu_init ()
#9 0x76c5460c in __libc_start_main (main=0x7efff214, argc=1993838592, argv=0x76c5460c <__libc_start_main+168>, init=0x11d68 <__libc_csu_init>, fini=0x11dc8 <__libc_csu_fini>, rtld_fini=0x76fdf9b8 <_dl_fini>, stack_end=0x7efff214)
at libc-start.c:247
#10 0x00010a78 in _start ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb)
但是，如果我放弃 nocopyreloc 指令，一切似乎都可以工作：
pi@raspberrypi:/tmp $ arm-linux-gnueabihf-g++ -g -Wall -O0 -ggdb segfault_check.cpp -o segv_test -lpthread
pi@raspberrypi:/tmp $ ./segv_test
Hello World
Threaded: Hello, World
Goodbye World
直到今天我还不知道nocopyreloc 选项。它通过我们用于交叉编译的 CMake 默认 CMAKE_EXE_LINKER_FLAGS 设置 工具链文件进入。 binutils documentation 声明：
nocopyreloc 禁用复制重定位的生产。
这没什么好解释的。
当我在我的开发机器 (linux x86_64) 上使用 g++ 7.2.0 编译程序时，我收到以下错误消息
./segv_test: Symbol `_ZSt4cout' causes overflow in R_X86_64_PC32 relocation
./segv_test: Symbol `_ZSt4cout' causes overflow in R_X86_64_PC32 relocation
./segv_test: Symbol `_ZSt4cout' causes overflow in R_X86_64_PC32 relocation
./segv_test: Symbol `_ZTVNSt6thread6_StateE' causes overflow in R_X86_64_PC32 relocation
Segmentation fault (core dumped)
这似乎暗示了问题的原因。显然加载器无法执行必要的重定位，但我不太了解该过程的细节。
我想知道我是否可以安全地放弃nocopyreloc 选项，或者我是否需要以不同的方式构建我的库或两者兼而有之？还是什么？
【问题讨论】：