[Solved] Golang test with cgo for shared object (.so) usage

README.md

Solved the problem with Attempt 2 with export LD_LIBRARY_PATH

Environment

## On-Premise
OS: Ubuntu 22.04.2
Golang Ver.: 1.21.0
GCC Ver.: 11.4.0

## Docker
Image: golang:lastest
Golang Ver.: 1.21.1
GCC Ver.: 12.2.0

Tree

## Attempt 1
.
├── go_sum
├── libsum.so
├── main.go
├── README.md
├── sum.c
└── sum.h

## Attempt 2
.
├── go_sum
├── lib
│   ├── libsum.so
│   ├── sum.c
│   └── sum.h
├── main.go
└── README.md

Enable CGO

$ CGO_ENABLED=1

Compile shared object with gcc

$ gcc -shared -o libsum.so sum.c

Compile golang exec

$ go build -o go_sum main.go
$ ./go_sum

Check

## On-Premise
$ ldd go_sum 
    linux-vdso.so.1 (0x00007ffc70e71000)
    libsum.so => not found
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f2aa6373000)
    /lib64/ld-linux-x86-64.so.2 (0x00007f2aa65a4000)

## Docker
$ ldd go_sum 
    linux-vdso.so.1 (0x00007ffd297fa000)
    libsum.so => not found
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f8865b7f000)
    /lib64/ld-linux-x86-64.so.2 (0x00007f8865d65000)

Error

$ ./go_sum
./go_sum: error while loading shared libraries: libsum.so: cannot open shared object file: No such file or directory

Solution

Add the LD_LIBRARY_PATH

$ export LD_LIBRARY_PATH=`pwd`/lib/

Ref:

1. ChatGPT
2. https://segmentfault.com/q/1010000022621510
3. https://serverfault.com/a/201711 [*]

main.go

package main

/* Select JUST 1 cgo config */

/* Attempt 1 */
/*
#cgo LDFLAGS: -L. -lsum
#include "sum.h"
*/

/* Attempt 2 */
/*
#cgo CFLAGS: -Ilib
#cgo LDFLAGS: -Llib -lsum
#include "sum.h"
*/

import "C"
import "fmt"

func main() {
	// Call the sum function from the shared library
	result := C.sum(5, 7)

	// Print the result
	fmt.Printf("Sum: %d\n", result)
}

sum.c

// sum.c
#include <stdio.h>
#include "sum.h"

int sum(int a, int b) {
    return a + b;
}

sum.h

// sum.h
#include <stdio.h>

int sum(int a, int b);