Example Go to C communication (cgo FFI)

README

go build -buildmode=c-archive c_ffi.go && 
gcc -pedantic -Wall -Wextra main.c c_ffi.a -lpthread -o test.elf

./test.elf

output:
x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, x, 

c_ffi.go

package main 
 
import ( 
    "C" 
    "unsafe" 
) 
 
//export fill_c_array_from_go 
func fill_c_array_from_go(data unsafe.Pointer, sz int) { 
    for i := 0; i < sz; i++ { 
        p := unsafe.Pointer(uintptr(data) + uintptr(i)) 
        ptr := (*uint8)(p) 
        *ptr = 'x' 
    } 
} 
 
func main() { 
        // Deliberately empty. 
}

main.c

#include "c_ffi.h" //generated by 'go build'
#include <stdio.h> 
#include <string.h> 
#include <unistd.h> 
 
int main(void) 
{ 
    char data[100]; 
    int i; 
 
    memset(data, 0, 100); 
 
    //this call triggers startup of Go runtime 
    fill_c_array_from_go(data, 100); 
 
    for (i = 0; i < 100; ++i) 
        printf("%c, ", data[i]); 
    printf("\n"); 
    return 0; 
}