stdarg x86_64 problems...

[Jonathan M Davis]

On Thursday, July 12, 2012 11:12:08 John Colvin wrote:
> When I compile the following code with -m32 and -m64 i get a
> totally different result, the documentation suggests that they
> should be the same...
> 
> import core.stdc.stdarg, std.stdio;
> 
> void main() {
> 	foo(0,5,4,3);
> }
> 
> void foo(int dummy, ...) {
> 	va_list ap;
> 
> 	for(int i; i<10; ++i) {
> 		version(X86_64) {
> 			va_start(ap, __va_argsave);
> 		}
> 		else version(X86) {
> 			va_start(ap, dummy);
> 		}
> 		else
> 			static assert(false, "Unsupported platform");
> 
> 		int tmp;
> 		va_arg!(int)(ap,tmp);
> 		writeln(ap," ", tmp);
> 	}
> }
> 
> when compiled with -m32 I get:
> 
> FF960278 5
> FF960278 5
> FF960278 5
> FF960278 5
> FF960278 5
> 
> and with -m64 I get:
> 
> 7FFFCDF941D0 5
> 7FFFCDF941D0 4
> 7FFFCDF941D0 3
> 7FFFCDF941D0 38
> 7FFFCDF941D0 -839302560
> 
> (the end stuff is garbage, different every time)
> 
> I'm uncertain, even after looking over the stdarg src, why this
> would happen. The correct output is all 5s obviously.

I expect that it's a bug. Please report it: http://d.puremagic.com/issues

64-bit support is relatively new, and while it works well overall, there _are_ 
a few serious bugs with it - particularly with regards to interacting with C 
(e.g. http://d.puremagic.com/issues/show_bug.cgi?id=5570 ). It's being worked 
on, but it's obviously still buggy in the interim, and it sounds like you 
found another bug with it.

- Jonathan M Davis