Question

我在这里缺少哪些链接器标志？

我尝试在Ubuntu 18.04 LTS上编译它，但是它失败了，它可以在Debian 9 docker镜像中工作：

#include <boost/dll.hpp>

// Trying to compile it with:
// g++ -o program -lboost_filesystem -ldl -lboost_system program.cpp

int main() {
  boost::dll::program_location();
  return 0;
}

我得到的错误是：

/tmp/ccKlWUUd.o: In function `__static_initialization_and_destruction_0(int, int)':
program.cpp:(.text+0x68): undefined reference to `boost::system::generic_category()'
program.cpp:(.text+0x74): undefined reference to `boost::system::generic_category()'
program.cpp:(.text+0x80): undefined reference to `boost::system::system_category()'
/tmp/ccKlWUUd.o: In function `boost::system::error_code::error_code()':
program.cpp:(.text._ZN5boost6system10error_codeC2Ev[_ZN5boost6system10error_codeC5Ev]+0x17): undefined reference to `boost::system::system_category()'
/tmp/ccKlWUUd.o: In function `boost::system::error_category::std_category::equivalent(int, std::error_condition const&) const':
program.cpp:(.text._ZNK5boost6system14error_category12std_category10equivalentEiRKSt15error_condition[_ZNK5boost6system14error_category12std_category10equivalentEiRKSt15error_condition]+0xb8): undefined reference to `boost::system::generic_category()'
program.cpp:(.text._ZNK5boost6system14error_category12std_category10equivalentEiRKSt15error_condition[_ZNK5boost6system14error_category12std_category10equivalentEiRKSt15error_condition]+0xf3): undefined reference to `boost::system::generic_category()'
/tmp/ccKlWUUd.o: In function `boost::system::error_category::std_category::equivalent(std::error_code const&, int) const':
program.cpp:(.text._ZNK5boost6system14error_category12std_category10equivalentERKSt10error_codei[_ZNK5boost6system14error_category12std_category10equivalentERKSt10error_codei]+0xb8): undefined reference to `boost::system::generic_category()'
program.cpp:(.text._ZNK5boost6system14error_category12std_category10equivalentERKSt10error_codei[_ZNK5boost6system14error_category12std_category10equivalentERKSt10error_codei]+0xf3): undefined reference to `boost::system::generic_category()'
program.cpp:(.text._ZNK5boost6system14error_category12std_category10equivalentERKSt10error_codei[_ZNK5boost6system14error_category12std_category10equivalentERKSt10error_codei]+0x1d2): undefined reference to `boost::system::generic_category()'
/tmp/ccKlWUUd.o: In function `boost::dll::detail::report_error(boost::system::error_code const&, char const*)':
program.cpp:(.text._ZN5boost3dll6detail12report_errorERKNS_6system10error_codeEPKc[_ZN5boost3dll6detail12report_errorERKNS_6system10error_codeEPKc]+0x2a): undefined reference to `dlerror'
/tmp/ccKlWUUd.o: In function `boost::filesystem::read_symlink(boost::filesystem::path const&, boost::system::error_code&)':
program.cpp:(.text._ZN5boost10filesystem12read_symlinkERKNS0_4pathERNS_6system10error_codeE[_ZN5boost10filesystem12read_symlinkERKNS0_4pathERNS_6system10error_codeE]+0x36): undefined reference to `boost::filesystem::detail::read_symlink(boost::filesystem::path const&, boost::system::error_code*)'
collect2: error: ld returned 1 exit status

这里的系统是：

gcc: 7.0.3
boost: 1.65.1
libc6: 2.73

Answer 1

您的构建命令顺序错误，顺序很重要。

GCC从左到右读取，在已经知道需要符号的情况下从库中获取符号。当您将program.cpp放到最后时，直到所有列出的库都已被识别并丢弃，您才知道这一点。

先放置program.cpp，然后放置所需的库。

g++ -o program program.cpp -lboost_filesystem -ldl -lboost_system

是的，这很奇怪。（即使它在Debian上也起作用，这很奇怪！尽管显然只有一些“最新” Linuxy发行版默认使用--as-needed，这才是导致您看到此行为的原因，表明该行为不一定得到保证。也许Debian 9完全是正确的。不这样做。）

更多信息：

Why does the order in which libraries are linked sometimes cause errors in GCC?

未定义对boost :: system :: generic_category（）的引用，尽管libs被赋予了g ++

1 个答案: