multiple definition when using cgo

Question

package main

/*
int add(int a, int b) {
    return a + b;
}
*/
import "C"
import "fmt"

func main() {}

func Test1() {
    fmt.Println(C.add(1, 3))
}

//export Test2
func Test2() {

}

Compile the programe:

dingrui@dingrui-PC:~/Projects/gotest/array$ go build -o libtest.so -buildmode=c-shared main.go 
# command-line-arguments
/tmp/go-build043762604/b001/_x002.o: In function `add':
./main.go:5: multiple definition of `add'
/tmp/go-build043762604/b001/_x001.o:/tmp/go-build/main.go:5: first defined here
collect2: error: ld returned 1 exit status

If I delete the "//export Test2" line, it compile successfully.

Answer 1

This behavior is documented here

Using //export in a file places a restriction on the preamble: since it is copied into two different C output files, it must not contain any definitions, only declarations. If a file contains both definitions and declarations, then the two output files will produce duplicate symbols and the linker will fail. To avoid this, definitions must be placed in preambles in other files, or in C source files.