I'll explain it with this sample:
First build libhello.a using ./libs/m.c:
#include <stdint.h>
extern uint64_t Add(uint64_t a, uint64_t b) {
return a + b;
}
For this test sample libhello.a is inside ./libs/ :
m.go
└───libs
m.c
libhello.a
Then go build this m.go working sample:
package main
//#cgo LDFLAGS: -L${SRCDIR}/libs -lhello
//#include <stdint.h>
//extern uint64_t Add(uint64_t a, uint64_t b);
import "C"
import (
"fmt"
)
func main() {
fmt.Println(C.Add(C.uint64_t(10), C.uint64_t(20))) // 30
}
output:
30
When the cgo directives are parsed, any occurrence of the string ${SRCDIR} will be replaced by the absolute path to the directory containing the source file. This allows pre-compiled static libraries to be included in the package directory and linked properly. For example if package foo is in the directory /go/src/foo:
// #cgo LDFLAGS: -L${SRCDIR}/libs -lfooWill be expanded to:
// #cgo LDFLAGS: -L/go/src/foo/libs -lfoo