C++ 使用 Makefile 捕获框架“多重定义”链接器错误答案

【问题标题】：C++ Catch framework 'multiple definition' linker errors with MakefileC++ 使用 Makefile 捕获框架“多重定义”链接器错误
【发布时间】：2017-06-18 19:55:09
【问题描述】：

针对 Google 流量提交我自己的答案。考虑 Makefile

  SHELL := /bin/bash                                                              

  run-tests: catch.o                                                              
      for x in *.cpp; do g++ $$x -o $$x.o catch.o && ./$$x.o; done                

  catch.o: catch.hpp                                                              
      g++ main.cxx -o catch.o

我正在为 Catch v1.9.5 编译单元测试。将以下内容与example given by their docs 进行比较：

// main.cxx
#define CATCH_CONFIG_MAIN
#include "catch.hpp"

// meta.cpp
#include "catch.hpp"

int foo(int a) {
    return -a;
}

TEST_CASE("foo", "[example]") {
    REQUIRE(foo(0) == 0);
    REQUIRE(foo(2) == -2);
    REQUIRE(foo(-2) == 2);
}

make 产生：

catch.o:(.rodata+0x0): multiple definition of `_IO_stdin_used'
/usr/lib/gcc/x86_64-redhat-linux/6.3.1/../../../../lib64/crt1.o:(.rodata.cst4+0x0): first defined here
catch.o:(.rodata+0x8): multiple definition of `__dso_handle'
/usr/lib/gcc/x86_64-redhat-linux/6.3.1/crtbegin.o:(.rodata+0x0): first defined here
catch.o: In function `_fini':
(.fini+0x0): multiple definition of `_fini'
/usr/lib/gcc/x86_64-redhat-linux/6.3.1/../../../../lib64/crti.o:(.fini+0x0): first defined here
catch.o: In function `_start':
(.text+0x0): multiple definition of `_start'
/usr/lib/gcc/x86_64-redhat-linux/6.3.1/../../../../lib64/crt1.o:(.text+0x0): first defined here
catch.o: In function `_init':
(.init+0x0): multiple definition of `_init'
/usr/lib/gcc/x86_64-redhat-linux/6.3.1/../../../../lib64/crti.o:(.init+0x0): first defined here
catch.o: In function `data_start':
(.data+0x0): multiple definition of `__data_start'
/usr/lib/gcc/x86_64-redhat-linux/6.3.1/../../../../lib64/crt1.o:(.data+0x0): first defined here
/usr/lib/gcc/x86_64-redhat-linux/6.3.1/crtend.o:(.tm_clone_table+0x0): multiple definition of `__TMC_END__'
catch.o:(.data+0x98): first defined here
/usr/bin/ld: error in catch.o(.eh_frame); no .eh_frame_hdr table will be created.
collect2: error: ld returned 1 exit status
Makefile:5: recipe for target 'run-tests' failed
make: *** [run-tests] Error 1

在run-tests 中删除对catch.o 的引用会导致链接器抱怨未定义的引用。 catch.o 和 main.cxx 有什么问题导致冗余定义？

【问题讨论】：

标签： c++ unit-testing linker linker-errors catch-unit-test

【解决方案1】：

catch.o Make 目标缺少 -c 标志，因此 GCC 过早地运行链接器步骤。尝试再次与实际测试套件链接导致 GCC 第二次从 Catch 生成定义，从而导致上述错误。解决方法是简单地将 -c 添加到 g++ main.cxx -o catch.o 以便编译 Catch，但等待链接直到它实际有要编译的测试。

【讨论】：