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

[Mike Parker via Digitalmars-d-learn]

On Tuesday, 29 August 2017 at 01:34:40 UTC, Johnson Jones wrote:

> import core.stdc.config;
> pragma(msg, c_long.sizeof);
>
> prints 4UL
>
> both on x64 and x86
>
> and and C:
>
> void foo()
> {
> 	int dummy;
> 	switch (dummy) {
> 	case sizeof(long) :
> 	case sizeof(long) :
> 		break;
> 	}
> }
>
>
> produces 4 on both x86 and x64. So, I'm not sure how you are 
> getting 8.

It's because you're on Windows. There, long/ulong are 4 bytes in 
both 32- and 64-bit. On Linux/Mac/*BSD, they're 4 in 32-bit and 8 
in 64-bit. This is why we have c_long and c_ulong, to hide those 
differences.