Go Fails to Find Procedure in DLL - windows

Question

Why Go fails to find the specified procedure in dll?
I have a my.dll library compiled for Windows x86 (The OS is Windows 7 x64; but I am using Go x86 binary - with LiteIDE - and the C# code is also explicitly compiled for x86 architecture). And I use it from C# and it works:
[DllImport("my.dll", EntryPoint = "my_function")]
public static extern double my_function(double x);
But when I try to use it (here I am trying just to find it) from Go by:
var (
dllMine = syscall.NewLazyDLL("my.dll")
my_function = dllMine.NewProc("my_function")
)
func main() {
err := my_function.Find()
if err != nil {
fmt.Println(err)
return
}
//...
}
It says Failed to find my_function procedure in my.dll: The specified procedure could not be found.. The my.dll file resides at the same directory with the generated .exe file. The entry point name ("my_function") does exists because it's working fine when is imported in C# and it does not say Failed to load my.dll: The specified module could not be found..
Actual pieces: The library I am trying to call is swedll32.dll which is the core library of Swiss Ephemeris (can be downloaded here - GNU) and just for testing this scenario the function to be called is swe_julday; for reproducing the error, with this signature:
double swe_julday(
int year, int month, int day, double hour,
int gregflag); /* Gregorian calendar: 1, Julian calendar: 0 */
Another thing is my GOROOT environment parameter is actually a NTFS junction point (so I can switch between x86 and x64 versions) - but I do not think it's relevant, because the output .exe app is being generated without any problem (just for the sake of confessing all my sins!).

Answer 1

I have downloaded your dll from http://www.astro.com/ftp/swisseph/sweph.zip to see if swe_julday function is in there:
C:\foo>dumpbin /exports swedll32.dll | find "swe_julday"
74 49 0000C440 _swe_julday#24
75 4A 0000D4A0 _swe_julday_d#24
And I don't see swe_julday function in there. Instead I see _swe_julday#24 function. So if I change your program to:
C:\foo>type foo.go
package main
import (
"syscall"
"fmt"
)
var (
dllMine = syscall.NewLazyDLL("swedll32.dll")
my_function = dllMine.NewProc("_swe_julday#24")
)
func main() {
err := my_function.Find()
if err != nil {
fmt.Println(err)
return
}
//...
}
it runs without any errors:
C:\foo>go run foo.go
C:\foo>