What to add when using c language functions in c++

When calling C language functions in C, you need to add the extern "C" modifier before the function declaration to avoid errors caused by mismatched calling conventions.

Call C language function in C

To use C language function in C program, you need to declare it in the function Add extern "C" modifier before.

Detailed description:

Due to the different calling conventions of C and C languages, directly calling C language functions in a C program will generate an error. extern "C" The function of the modifier is to interpret the function declaration as a C language style declaration, thereby avoiding the problem of calling convention mismatch.

The steps to use the extern "C" modifier are as follows:

1. Declare the C language function in the header file:

   extern "C" {
    int add(int a, int b);
   }

2. Use C language functions in C files:

   int main() {
    int result = add(10, 20);
    std::cout << "Result: " << result << std::endl;
    return 0;
   }

By adding extern "C" modifier, the C compiler knows to treat the add function as a C-style function and handles the calling convention correctly. This allows seamless use of C language functions in C programs.

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