> Please take the hostility down a notch. I don't see why it's necessary.
I apologize (to both you and Kai) if that's how this came across. That
was not my intent. I routinely use weekends to work on new puzzles.
The reason I suggested it would give him plenty to think about over the
weekend is that's when I do my best thinking.
However, it would be utterly true to say that I am both insecure and
defensive, and my posts no doubt reflect that. I'm a gcc newbie here
trying convince long-time experts that I know what I'm talking about in
this really technical area. That said, I will try harder to keep
"attitude" out of my posts. Continue to clobber me as appropriate.
> This is not the behavior I see. If I fix your buggy code to read
My goal with this (admittedly ugly) code was threefold:
1) Minimum code necessary to clearly reproduce the problem.
2) Allow for easier experimentation without changing a system include
file. Knowing me, I'd leave some bad definition in the header, then
wonder why nothing worked anymore.
3) Minimize the confusion over which definition of __stosb is being used
(see below).
> Sorry, I don't see any unexpected behavior here (solely by comparing
> to MSVC output). So either I'm misunderstanding you, or what is
> currently in MinGW-w64 is correct.
When I compile your code, I don't see the problem either. However,
that's because when using your code, we aren't using the inline
assembler definition from winnt.h. A quick look at the disassembly from
my attempt to compile your code shows:
402ce4: call 402af0 <__stosb>
If we were using the inline code from winnt.h, there would be no "call",
just the asm. If I change your code to add:
#include <windows.h>
right after assert.h, I see the same problem again (0 2). To see it
work correctly, modify winnt.h to add the memory clobber:
__CRT_INLINE VOID __stosb(PBYTE Dest,BYTE Data,SIZE_T Count)
{
__asm__ __volatile__
(
"rep; stosb" :
[Dest] "=D" (Dest), [Count] "=c" (Count) :
"[Dest]" (Dest), "a" (Data), "[Count]" (Count)
: "memory"
);
}
NB: I don't believe this definition of __stosb is quite right either.
But it's closer. And it does illustrate the behavior of the memory
clobber, which was the purpose of the post.
dw
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