C callbacks getting a value of 0! Bug in D?

[Steven Schveighoffer via Digitalmars-d-learn]

On 8/27/17 10:17 PM, Johnson Jones wrote:
> Looking at the assembly shows something like this:
> 
> 0041ea98  push 0x0
> 0041ea9a  push 0x0
> 0041ea9c  push 0x0
> 0041ea9e  push dword 0x100
> 0041eaa3  mov ecx, [typeid(PaStreamParameters)+0xe36fc (0x80d4cc)]
> 0041eaa9  mov eax, [fs:0x2c]
> 0041eaaf  mov edx, [eax+ecx*4]
> 0041eab2  push dword [edx+0x1c]
> 0041eab8  push dword [edx+0x18]
> 0041eabe  push dword [ebp-0x54]
> 0041eac1  push dword [ebp-0x5c]
> 0041eac4  mov ebx, PA.stream (0x823f30)
> 0041eac9  push ebx
> 0041eaca  call dword near [Pa_OpenStream (0x823f18)]
> 
> I noticed that those 0's were the values being fed in to the function.
> 
> I remember converting c_ulong's to ulong's and that they were probably 
> uint's in D. Converting those fixed the problem and the callback is now 
> called! I converted all the ulongs to uint's but there were a few longs 
> and I don't know if they are c_longs or d_longs...
> 
> Anyways, At least I'm on the right track.
> 

For C/C++ interaction, always use c_... types if they are available. The 
idea is both that they will be correctly defined for the width, and also 
it will mangle correctly for C++ compilers (yes, long and int are 
mangled differently even when they are the same thing).

-Steve