There is a github issue here for this, but it seems not to have been merged as of Go 1.10.3 (the version I am using right now).
Anyway, the github issue links to a changeset with the respective function from which I extracted the code to do what you want here:
var (
kernel32 = syscall.NewLazyDLL("kernel32.dll")
procGetProcAddress = kernel32.NewProc("GetProcAddress")
)
// GetProcAddressByOrdinal retrieves the address of the exported
// function from module by ordinal.
func GetProcAddressByOrdinal(module syscall.Handle, ordinal uintptr) (uintptr, error) {
r0, _, _ := syscall.Syscall(procGetProcAddress.Addr(), 2, uintptr(module), ordinal, 0)
proc := uintptr(r0)
if proc == 0 {
return 0, syscall.EINVAL
}
return proc, nil
}
For completeness, here is the full example with which I tested this, using the Dependecy Walker I found that the first function in kernel32.dll is AcquireSRWLockExclusive
and using the new function it shows that the proc addresses really match.
package main
import (
"fmt"
"syscall"
)
func main() {
dll, err := syscall.LoadDLL("kernel32.dll")
check(err)
want, err := syscall.GetProcAddress(dll.Handle, "AcquireSRWLockExclusive")
check(err)
fmt.Println(want)
first, err := GetProcAddressByOrdinal(dll.Handle, 1)
check(err)
fmt.Println(first)
}
func check(err error) {
if err != nil {
panic(err)
}
}
var (
kernel32 = syscall.NewLazyDLL("kernel32.dll")
procGetProcAddress = kernel32.NewProc("GetProcAddress")
)
// GetProcAddressByOrdinal retrieves the address of the exported
// function from module by ordinal.
func GetProcAddressByOrdinal(module syscall.Handle, ordinal uintptr) (uintptr, error) {
r0, _, _ := syscall.Syscall(procGetProcAddress.Addr(), 2, uintptr(module), ordinal, 0)
proc := uintptr(r0)
if proc == 0 {
return 0, syscall.EINVAL
}
return proc, nil
}