Mirror of forum.nim-lang.org

7632 :: Dll with a different entry point as Dllmain

• ludisposed (orginal) [2021-03-15T14:39:55+01:00] view original

  As described by the title, is it possible to export other function from a Dll as opposed to DllMain?

---

• PMunch (orginal) [2021-03-16T10:07:09+01:00] view original

  Yes, you just attach the pragmas {.stdcall,exportc,dynlib.} to the procedure and you can export any procedure just fine.

---

• Araq (orginal) [2021-03-16T10:18:20+01:00] view original

  Compile with --noMain and use some linker command to specify the entry point's name. Maybe it's possible, I never had to do that.

---

• ludisposed (orginal) [2021-03-17T11:09:30+01:00] view original

  @PMunch Thanks, it was actually as simple as that. You do however still need to add a DllMain and specify --noman in the compiler

  Example:

  
  import winim
  import os
  
  proc NimMain() {.cdecl, importc.}
  proc DllMain(hinstDLL: HINSTANCE, fdwReason: DWORD, lpvReserved: LPVOID) : BOOL {.stdcall, exportc, dynlib.} =
    NimMain()
    return true
  
  proc entry(): void {.stdcall, exportc, dynlib.} =
    AllocConsole()
    discard stdout.reopen("CONOUT$", fmWrite)
    stdout.write "TEST!"
    
    while GetAsyncKeyState(VK_END) == 0:
      sleep(500)
    
    stdout.close()
    FreeConsole()
  Run

---

• ludisposed (orginal) [2021-03-17T11:12:13+01:00] view original

  I am having another problem, the entire reason to use a different entrypoint as opposed to DllMain was that I needed to use threads in my Dll, but whenever I compile the dll with --threads:on it won't work (I guess problems with the LoadLibrary underneath, any suggestions how to use threads with dll's?

  
  import winim
  import os
  
  var chan: Channel[string]
  
  proc thread1() =
    chan.send("This is some data")
  
  proc thread2() =
    var msg = chan.recv()
    stdout.write msg
  
  proc NimMain() {.cdecl, importc.}
  proc DllMain(hinstDLL: HINSTANCE, fdwReason: DWORD, lpvReserved: LPVOID) : BOOL {.stdcall, exportc, dynlib.} =
    NimMain()
    return true
  
  proc entry(): void {.stdcall, exportc, dynlib.} =
    AllocConsole()
    discard stdout.reopen("CONOUT$", fmWrite)
    stdout.write "TEST!"
    
    var worker1: Thread[void]
    var worker2: Thread[void]
    
    chan.open()
    createThread(worker1, thread1)
    createThread(worker2, thread2)
    worker2.joinThread()
    chan.close()
    
    while GetAsyncKeyState(VK_END) == 0:
      sleep(500)
    
    stdout.close()
    FreeConsole()
  Run

  compiled with nim c --app:lib --nomain --os:windows --cpu:amd64 --threads:on

---