c How to call golang

C language and Golang are both commonly used programming languages. Although they are different in syntax and application scenarios, they both have their own advantages and disadvantages. Therefore, different programming languages ​​will be selected for different application requirements. But if we want to integrate C language and Golang, we need to understand how to achieve interoperability between the two languages.

This article will introduce how to call Golang program in C language. C language is an early programming language and is widely used in system development, while Golang is a newer programming language that is favored for its efficient concurrency performance. Integrating the two allows us to take into account their respective advantages and implement applications with richer functions.

Prerequisite

Before we start trying to call Golang in C language, we must ensure that Golang has been installed in the environment. You can enter the following command in the terminal to check:

$ go version

If the Golang version information can be output in the terminal, it means the installation has been successful.

Calling Go functions

Golang provides a C language-compatible API, which can be used directly in C programs. We can use this API to call a Golang function from a C program. Here are the steps:

1. First, when defining a Golang function, you need to add //export before the function name. This exposes the functional interface to the C program.

package main

import "C"

//export Add
func Add(x, y int) int {
    return x + y
}

In this example, we define an Add function that accepts two integers and returns their sum. Through the //export command, we expose the interface of this function to the C program.

2. Next, we need to define a function pointer in the C program to save the handle when we call the Golang function.

typedef struct {
    uintptr_t p;
} GoInt;

typedef struct {
    uintptr_t p;
    int n;
} GoString;

typedef struct {
    uintptr_t p;
    int n;
} GoSlice;

typedef struct {
    uintptr_t p;
    uintptr_t len;
    uintptr_t cap;
} GoSliceHeader;

typedef struct {
    uintptr_t p;
    uintptr_t len;
} GoStringHeader;

typedef struct {
    uintptr_t p;
    int argc;
    void *argv;
} GoArgs;

typedef struct {
    uintptr_t p;
    int type; /* 0 = panic, 1 = error */
    char *message;
} GoError;

typedef int (*AddFunc)(int, int);

AddFunc NewAddFunc() {
    static GoInt Add;
    static int once = 1;
    if (once) {
        once = 0;
        // Call the "Add" function implemented in Go
        const char* name = "Add";
        void* symbol = dlsym(RTLD_DEFAULT, name);
        if (symbol == NULL) {
            return NULL;
        }
        Add.p = (uintptr_t)symbol;
    }
    return (AddFunc)Add.p;
}

3. Now we can use the function pointer to call the Golang function Add.

int main() {
    AddFunc add = NewAddFunc();
    if (add == NULL) {
        printf("Failed to find 'Add' function.
");
        return -1;
    }
    int result = add(1, 2);
    printf("The result is %d.
", result);
    return 0;
}

In this example, we define NewAddFunc to get the function pointer of the Add function. If the function pointer is not successfully obtained, an error message is output and the program exits. If the function pointer is obtained, we can directly call the Add function through it, input two integer parameters, and output the calculation result through the printf function.

Note: Before compiling, you need to add the following parameters to the command line to ensure that the compiled program can correctly link to the Golang library:

$ gcc -o cgo_example cgo_example.c -Wl,-rpath,$GOPATH/src/github.com/YourUserName/YourProjectName

Conclusion

Through the above Steps, we can easily call Golang functions in C programs to achieve functions that are difficult to achieve in original C programs. At the same time, we have also seen that when performing this process, we need to define function pointers and data structures to ensure the correct transfer of data and the correct matching of types. In practical applications, we need to make flexible adjustments and modifications according to actual conditions.

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