Run Time Error 49 Bad DLL Calling Convention

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Dear Experts,

I am trying to call a subroutine in my Dll from VBA but keep getting the error "Run Time Error 49 Bad DLL Calling Convention". Any suggestions on what I am doing wrong?

<code>Declare Sub init_gen_rand Lib "SFMT.dll" (seed As Double)</code>

<code>__declspec( dllexport ) void init_gen_rand(uint32_t seed);</code>

In this other example, I am calling a function with no argument and do get a return number but the return numbers are sometimes negative even though the data type is an unsigned integer uint32_t. What is going wrong?

Declare Function gen_rand32 Lib "SFMT.dll" () As Double

<code>__declspec( dllexport ) uint32_t gen_rand32(void);</code>

Thanks for your help,
Neil

Posted 22-Jul-10 8:30am

Neil Sheridan

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3 solutions

Solution 2

Thanks, any suggestions? I have also tried Long with the same result.

Declare Function gen_rand32 Lib "C:\Users\Neil\Documents\Visual Studio 2010\Projects\SFMT\Release\SFMT.dll" () As Long
Declare Sub init_gen_rand Lib "C:\Users\Neil\Documents\Visual Studio 2010\Projects\SFMT\Release\SFMT.dll" (seed As Long)

Posted 22-Jul-10 20:07pm

Neil Sheridan

Solution 1

A uint32 is not a double. I'd say that's the issue.

Posted 22-Jul-10 11:59am

Christian Graus

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Dalek Dave 22-Jul-10 18:22pm

Yep, I concur with thee oh mighty one.
Seems reasonable. Damn typing! :)

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Sauro Viti · Accepted Answer · 2010-07-22T20:42:00

Solution 3

The VBA can succesfully import only function declared with the __stdcall calling convention; try this way:

VB

Declare Function gen_rand32 Lib "SFMT.dll" () As Long

C++

__declspec( dllexport ) uint32_t __stdcall gen_rand32(void);

Posted 22-Jul-10 20:42pm

Sauro Viti

Comments

Neil Sheridan 23-Jul-10 5:13am

Thanks! That fixed the calling question. I am still getting negative numbers but I am assuming that if something meant for an UINT32_t is instead passed into a Long then when I will end up keeping the sign. Therefore I will have to make the number absolute somewhere else in the code.