cmd/cgo: can't build with both inline C function define and Go function export

[xiezhenye]

can't build with both inline C function define andGo function export

code:

package main

//
// int add(int a, int b) {
//   int ret = a + b;
//   return ret;
// }
//
// extern void foo();
//
import "C"

import (
  "fmt"
)

//export foo
func foo() {
}

func main() {
  var n int32
  n = int32(C.add(C.int(2), C.int(3)))
  fmt.Println(n)
}

got compile error:

# GOROOT=/opt/go-1.4.2 /opt/go-1.4.2/bin/go build cgo.go
# command-line-arguments
/tmp/go-build570506490/command-line-arguments/_obj/cgo.cgo2.o: In function `add':
./cgo.go:5: multiple definition of `add'
/tmp/go-build570506490/command-line-arguments/_obj/_cgo_export.o:/root/test/testgoc/cgo.go:5: first defined here
collect2: error: ld returned 1 exit status

cgo writes the inline C functions both in cgo.cgo2.c and _cgo_export.h

[minux]

This is working as intended and it's documented. http://golang.org/cmd/cgo/#hdr-C_references_to_Go 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. Definitions must be placed in preambles in other files, or in C source files. A trick is that if you only declare functions in the cgo preamble, then you can label the function static.