当我改变g ++参数的顺序时,为什么我的程序无法链接？

Question

可能重复:
为什么gcc中'-l'选项的顺序很重要？

我开始学习Boost单元测试框架.我有一个最小的测试套件:

#define BOOST_TEST_MAIN
#define BOOST_TEST_DYN_LINK 
#include <boost/test/unit_test.hpp>

BOOST_AUTO_TEST_CASE( test1 ) {
    BOOST_CHECK( 2 == 1 );
}

首先我编译源代码:

g++ -c src/tests.cc -o src/tests.o

这完成没有错误.然后我可以链接如下:

g++ -o tests src/tests.o -lboost_unit_test_framework

这也完成没有错误.生成的二进制文件执行预期结果.但是,如果我交换了src/tests.o和的顺序-lboost_unit_test_framework,我会收到链接器错误:

g++ -o tests -lboost_unit_test_framework src/tests.o

src/tests.o: In function `main':
tests.cc:(.text+0x29): undefined reference to `boost::unit_test::unit_test_main(bool (*)(), int, char**)'
src/tests.o: In function `test1::test_method()':
tests.cc:(.text+0x9d): undefined reference to `boost::unit_test::unit_test_log_t::set_checkpoint(boost::unit_test::basic_cstring, unsigned int, boost::unit_test::basic_cstring)'
tests.cc:(.text+0x146): undefined reference to `boost::test_tools::tt_detail::check_impl(boost::test_tools::predicate_result const&, boost::unit_test::lazy_ostream const&, boost::unit_test::basic_cstring, unsigned int, boost::test_tools::tt_detail::tool_level, boost::test_tools::tt_detail::check_type, unsigned int, ...)'
src/tests.o: In function `__static_initialization_and_destruction_0(int, int)':
tests.cc:(.text+0x24d): undefined reference to `boost::unit_test::ut_detail::auto_test_unit_registrar::auto_test_unit_registrar(boost::unit_test::test_case*, unsigned long)'
src/tests.o: In function `boost::unit_test::unit_test_log_t::unit_test_log_t()':
tests.cc:(.text._ZN5boost9unit_test15unit_test_log_tC2Ev[_ZN5boost9unit_test15unit_test_log_tC5Ev]+0x21): undefined reference to `vtable for boost::unit_test::unit_test_log_t'
src/tests.o: In function `boost::unit_test::make_test_case(boost::unit_test::callback0 const&, boost::unit_test::basic_cstring)':
tests.cc:(.text._ZN5boost9unit_test14make_test_caseERKNS0_9callback0INS0_9ut_detail6unusedEEENS0_13basic_cstringIKcEE[boost::unit_test::make_test_case(boost::unit_test::callback0 const&, boost::unit_test::basic_cstring)]+0x1d): undefined reference to `boost::unit_test::ut_detail::normalize_test_case_name(boost::unit_test::basic_cstring)'
tests.cc:(.text._ZN5boost9unit_test14make_test_caseERKNS0_9callback0INS0_9ut_detail6unusedEEENS0_13basic_cstringIKcEE[boost::unit_test::make_test_case(boost::unit_test::callback0 const&, boost::unit_test::basic_cstring)]+0x5d): undefined reference to `boost::unit_test::test_case::test_case(boost::unit_test::basic_cstring, boost::unit_test::callback0 const&)'
src/tests.o: In function `boost::unit_test::unit_test_log_t::~unit_test_log_t()':
tests.cc:(.text._ZN5boost9unit_test15unit_test_log_tD2Ev[_ZN5boost9unit_test15unit_test_log_tD5Ev]+0xb): undefined reference to `vtable for boost::unit_test::unit_test_log_t'
collect2: ld returned 1 exit status

为什么我的参数的顺序会导致链接器错误？

Answer 1

当GCC执行链接时,将特别处理库:只从库中填充命令行列表中库之前的目标文件中缺少的符号.如果在库之后还有其他目标文件,则不会在库中查找该对象中缺少的符号.

简而言之,首先列出目标文件,最后列出库.