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9298 :: Creating a vb6 dll compatible and Returning String

• hubdev (orginal) [2022-07-11T16:56:49+02:00] view original

  Nim Compiler Version 1.6.6 [Windows: i386] Compiled at 2022-05-05 Copyright (c) 2006-2021 by Andreas Rumpf active boot switches: -d:release

  Cmd Compile nim c --cpu:i386 -d:release --app:lib --nomain mydll.nim

  Hi there, I was able to return a Long value, now I'm trying to get string values.

  I googled to find some exemples and find out here: https://my.oschina.net/yuekcc/blog/775990

  I'm getting this error:

  

  VB6:

  
  Private Declare Function MyStr Lib "mydll.dll" (ByVal s As String) As String
  Private Declare Function toVBString Lib "mydll.dll" (ByVal s As String) As String
  Private Declare Function return_multiply Lib "mydll.dll" Alias "return_multiply@8" (ByVal a As Long, ByVal b As Long) As Long
  
  Private Sub Form_Click()
    MsgBox MyStr("?")  'error
    MsgBox return_multiply(5, 4) 'ok
  End Sub
  Run

  Another question, why the Alias has @8 at the end? return_multiply@8

  Nim:

  
  import encodings
  
  const
      vbCodePage = "GB2312"
      vbTrue* = 1
      vbFalse* = 0
  
  type
      VBString* = cstring
      VBBoolean* = int32
  
  proc MyStr*(): cstring {.stdcall, exportc, dynlib.} =
    result = $"teste"
  
  proc fromVBString*(a: VBString): string =
      return encodings.convert($a, "UTF-8", vbCodePage)
  
  proc toVBString*(a: string): VBString =
      return VBString(encodings.convert(a, vbCodePage, "UTF-8"))
  
  proc return_multiply*(a, b: int): int {.stdcall, exportc, dynlib.} =
      a * b
  Run

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