When to use extern "C"?

Question

I know how to use it extern "C", but what are the conditions when you should use it?

extern "C"tells the C ++ compiler not to do any code name manipulation inside curly braces. This allows you to call C functions from within C ++.

For instance:

#include <string.h>

int main()
{
    char s[] = "Hello";
    char d[6];

    strcpy_s(d, s);
}

While this is compiling on VC ++. But sometimes it is written as:

extern "C" {   
#include <string.h>  
}

I do not see the point. Can you give a real example where extern "C"necessary?

Answer 1

You use extern "C"to prevent name manipulation inside the header files and your C ++ object files for libraries or objects that have already been compiled without distortion.

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#ifdef __cplusplus
    extern "C" {
#endif

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#ifdef __cplusplus
    }
#endif

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Answer 2

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Answer 3

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module.h

int f(int arg);

module.c

int f(int arg) {
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}

main.cpp

#include "module.h"

int main() {
  f(42);
}

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module.h

#ifdef __cplusplus
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#endif

int f(int arg);

#ifdef __cplusplus
  }
#endif

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Answer 5

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Answer 6

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