Re: 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.