integer division in Go called from C

Question

I am able to perform integer division in go by this program :

package main

import "fmt"

func main() {
 a := 10
 b := 5
    fmt.Println(a/b)
}

Then I made a program in go that has functions for +, -, * and /. and I made a program in C that calls each of these functions and performs arithmetic operations. Except division, the code works fine.

The go file with the functions is : (calc.go)

package main

func Add(a, b int) int {
    return a + b
}
func Sub(a, b int) int {
    return a - b
}
func Mul(a, b int) int {
    return a * b
}
func Div(a, b int) int {
    return a / b
}

And the C program that calls these functions is : (calcc.c)

#include <stdio.h>

extern int go_add(int, int) __asm__ ("main.Add");
extern int go_sub(int, int) __asm__ ("main.Sub");
extern int go_mul(int, int) __asm__ ("main.Mul");
extern int go_div(int, int) __asm__ ("main.Div");

int menu()
{
  int op;
  printf("\n1 add");
  printf("\n2 sub");
  printf("\n3 mul");
  printf("\n4 div");
  printf("\nEnter your choice : ");
  scanf("%d", &op);
  return op;
}
int main() {


  int op, ch, result, a, b;

  do{ 
    op= menu();

    printf("First number  : ");
    scanf("%d", &a);
    printf("Second number : ");
    scanf("%d", &b);

    switch(op)
    {
       case 1:
        result = go_add(a, b);
    printf("Result : %d" , result);
        break;
       case 2:
        result = go_sub(a, b);
    printf("Result : %d" , result);
        break;
       case 3:
        result = go_mul(a, b);
    printf("Result : %d" , result);
    break;
       case 4:
        result = go_div(a, b);
    printf("Result : %d" , result);
    break;
       default:
        printf("Invalid choice ! ");
    }
    printf("\nAnother operation? (1 if yes) : ");
    scanf("%d", &ch);
  } while(ch==1);
  printf("\nThank you!");
}

I compiled on the terminal using the commands :

gccgo -c calc.go

• and

gcc calc.o calcc.c -o main

And got this error : undefined reference to `__go_runtime_error' collect2: error: ld returned 1 exit status

How should I fix this?

Answer 1

You need to link using gccgo and not with normal gcc. Normal gcc doesn't know that it ought to link against the go runtime (libgo).

Depending on your configuration, you might also need to specify where the runtime library can be found. For example by embedding it statically or by making it available in the LD_LIBRARY_PATH environment variable. Example:

gccgo -static-libgo calc.o calcc.o -o main

For more information, check Setting up and using gccgo.