Inline Assembly, MOV, and Memory Operand Constraint

[Jeffrey Walton]

On Wed, Jun 15, 2011 at 5:13 AM, Andrew Haley <aph@redhat.com> wrote:
> 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));
> }
>
Thanks Andrew - that was it. I thought I tried that variation (perhaps
I did not use %%eax).

Jeff