如何编译和链接C ++代码与编译的C代码？ [英] How do I compile and link C++ code with compiled C code?

问题描述

我希望能够使用 Cmockery 来模拟从C ++代码调用的C函数我在测试。为此，我已将Cmockery示例重命名为 run_tests.c 到run_tests.cpp，并试图编译并链接到cmockery.c：

  g ++ -m32 -DHAVE_CONFIG_H -DPIC -I ../cmockery-0.1.2 -I / usr / include / malloc -c run_tests.cpp -o obj / run_tests.o 
 gcc -m32 -DHAVE_CONFIG_H -DPIC -Wno-format -I ../cmockery-0.1.2 -I / usr / include / malloc -c ../cmockery-0.1.2/cmockery.c -o obj / cmockery.o 
 g ++ -m32 -o run_tests obj / run_tests.o obj / cmockery.o 
  

前两个命令行（编译）是成功的，但在最后我得到：

 未定义的符号：
_run_tests（UnitTest引用自：
 _main in run_tests.o 
 ld：符号（s）未找到
 collect2：ld返回1退出状态
  

那个未定义的符号来自run_tests.cpp的第29行：

  return run_tests（tests）; 
  

run_tests（）函数在cmockery.c中定义。

阅读将C ++代码与'gcc'链接（无

  gcc -lstdc ++ -m32 -o run_tests obj / run_tests.o obj / cmockery.o 
  

但是得到了相同的结果：

 未定义的符号：
_run_tests（UnitTest const *，unsigned long），引用来自：
 run_tests.o中的_main 
 ld：symbol （s）not found 
 collect2：ld返回1退出状态
  

如何编译和链接C ++代码，以便它找到C代码中的符号？

解决方案

我认为你可以通过添加thinkg来连接C ++以下是围绕cmockery.h文件的内容：

开始或接近开始：

  #if defined（__ cplusplu s）
 externC{
 #endif 
  

在或接近end：

  #if defined（__ cplusplus）
} 
 #endif 
  
 
 $ b 
这样一来，使用C源代码头就会忽略 externC声明的一部分，但是当头文件包含在C ++构建中时，编译器将被正确地告知该头文件中声明的链接使用C语义。
 
 
 
对于快速n-dirty测试或者如果你不想修改标题，你可以试试： 
 
 
  extern C{
 #includecmockery.h
} 
  
但是我的首选项是在标题中放置 externC块（并且只包含需要的东西 - 可能需要一些分析）。
 
I want to be able to use Cmockery to mock C functions called from C++ code I'm testing.  As a step towards that, I've renamed the Cmockery example run_tests.c to run_tests.cpp, and am attempting to compile and link it with cmockery.c:
g++ -m32 -DHAVE_CONFIG_H -DPIC -I ../cmockery-0.1.2 -I /usr/include/malloc -c run_tests.cpp -o obj/run_tests.o
gcc -m32 -DHAVE_CONFIG_H -DPIC -Wno-format -I ../cmockery-0.1.2 -I /usr/include/malloc -c ../cmockery-0.1.2/cmockery.c -o obj/cmockery.o
g++  -m32 -o run_tests obj/run_tests.o obj/cmockery.o
The first two command lines (to compile) are successful, but after the last I get:
Undefined symbols:
  "_run_tests(UnitTest const*, unsigned long)", referenced from:
      _main in run_tests.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
That undefined symbol is from line 29 of run_tests.cpp:
return run_tests(tests);
The run_tests() function is defined in cmockery.c.

After reading "Linking C++ code with 'gcc' (without g++)", I tried:
gcc -lstdc++ -m32 -o run_tests obj/run_tests.o obj/cmockery.o
But got the same result:
Undefined symbols:
  "_run_tests(UnitTest const*, unsigned long)", referenced from:
      _main in run_tests.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
How do I compile and link C++ code so it finds the symbols in C code?
解决方案
I think that you can get thinkgs to link from C++ by adding the following around the contents of the cmockery.h file:

At or near the beginning:
#if defined(__cplusplus)
extern "C" {
#endif
At or near the end:
#if defined(__cplusplus)
}
#endif
That way, use of the header in C sources will ignore the extern "C" part of the declaration, but when the header is include in C++ builds, the compiler will be properly told that the linkage for the declarations in that header use C semantics.

For a quick-n-dirty test or if you'd rather not modify the header, you can try:
extern "C" {
#include "cmockery.h"
}
but my preference would be to put the extern "C" block in the header (and only around the stuff that's required - that might need a bit of analysis).

                        
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