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Re: Inline Assembly, MOV, and Memory Operand Constraint


On 15/06/11 08:25, Jeffrey Walton wrote:
> Hi All,
> 
> I have a question on inline assembly. For my first experiment, I'm
> trying to read the flags register. Intuitively, I'm trying to perform
> the following:
>     mov %eax, result
> 
> The assembler does not take the simple syntax (see [1], [2]), andI'm
> having trouble getting the statement right. I've tried lots of
> variations on the following, but have yet to find success.
>     unsigned int result;
>     ...
>     asm volatile("mov %eax, result" : "=m(result)");

Should be

unsigned int result;

void ping() {
  asm volatile("mov %%eax, %0" : "=m"(result));
}


	.comm	result,4,4
	.text
.globl ping
	.type	ping, @function
ping:
	pushl	%ebp
	movl	%esp, %ebp
#APP
# 4 "t.c" 1
	mov %eax, result
# 0 "" 2
#NO_APP
	popl	%ebp
	ret

Andrew.


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