What is this error (process 16500) exited with code -1073740940. ?

Question

Hi,

When I build my small Visual Basic Console program I get this message on the console;

"
H:\My Program Projects MS VS 2019 Community\Swe_Version Function Testing\bin\Debug\netcoreapp3.1\Swe_Version Function Testing.exe (process 16500) exited with code -1073740940."

What does this mean?

Please let me know how to rectify it.

Thanks
VKSBK

Answer 1

I suspect that even when you tried to use StringBuilder that you declared the function as returning a String. This is a problem. The char* pointer that the unmanaged function _swe_version@4 returns will not be properly marshaled to a managed string and this is a source of the heap corruption error.

This will fail -

    Public Declare Function swe_version Lib "swedll32.dll" Alias "_swe_version@4" (ByVal strVersion As StringBuilder) As String  

This will succeed -

    Public Declare Function swe_version Lib "swedll32.dll" Alias "_swe_version@4" (ByVal strVersion As StringBuilder) As IntPtr  

This will succeed -

    Public Declare Sub swe_version Lib "swedll32.dll" Alias "_swe_version@4" (ByVal strVersion As StringBuilder)  
  

Answer 2

Dear cooldadtx & RLWA32,

Good news :-)

Imports System.Text  
  
Module Module1  
  
    Sub Main()  
        'To Call Ephemeris Path  
        swe_set_ephe_path("C:\sweph\ephe")  
  
        Dim Sweph_Version As New StringBuilder(128)  
        swe_version(Sweph_Version)   
  
        Console.WriteLine(Sweph_Version)  
        Console.ReadLine()  
  
    End Sub  
  
  
    Private Declare Sub swe_set_ephe_path Lib "swedll32.dll" _  
        Alias "_swe_set_ephe_path@4" (  
          ByVal path As String  
        )  
    
    Private Declare Function swe_version Lib "swedll32.dll" _  
        Alias "_swe_version@4" (  
          ByVal svers As StringBuilder  
        ) As IntPtr  
    ' svers must be able to hold 256 bytes  
  
End Module  

This works fine.

Then, I tried this:

Module Module1  
  
    Sub Main()  
        'To Call Ephemeris Path  
        swe_set_ephe_path("C:\sweph\ephe")  
  
        Dim Sweph_Version As String = Space(256)  
        swe_version(Sweph_Version)  
  
        Console.WriteLine("Sweph_Version : " & Sweph_Version)  
        Console.ReadLine()  
  
    End Sub  
  
  
    Private Declare Sub swe_set_ephe_path Lib "swedll32.dll" _  
        Alias "_swe_set_ephe_path@4" (  
          ByVal path As String  
        )  
  
    Private Declare Function swe_version Lib "swedll32.dll" _  
        Alias "_swe_version@4" (  
          ByVal svers As String  
        ) As IntPtr  
    ' svers must be able to hold 256 bytes  
  
End Module  

This also worked okay. Please note, here I used "ByVal svers As String) As IntPtr".

"ByRef svers As String) As IntPtr" failed.

Thanks
Kind regards

VKSBK

Answer 3

Hi,

Why did all of a sudden few replies disappear?

VKSBK

Answer 4

As I previously indicated, the heap corruption was caused by the interop attempting to marshal the char* return value to a managed string. When the function declarations use IntPtr, that problem is resolved.

Answer 5

Dear RLWA32,

"the heap corruption was caused by the interop attempting to marshal the char* return value to a managed string. When the function declarations use IntPtr, that problem is resolved".

Can you please explain it to me in simple language. I still don't know what "IntPtr" is? Is it "Integer Pointer"???

Googling gave me this;
https://learn.microsoft.com/en-us/dotnet/api/system.intptr?view=net-5.0

A bit too complicated....

Kind regards
VKSBK