Re: help with __sync for "long long" types

[Preeti Sharma <pritis at gmail dot com>]

Hello Andrew ,

Thanks for the response :
also wanted you to know that the problem is only for a 64 bit value ;
it compiles fine for a 32 bit int.

Thanks .

Preeti

On Wed, Jul 7, 2010 at 8:43 AM, Andrew Haley <aph@redhat.com> wrote:
> On 07/07/2010 04:26 PM, Preeti Sharma wrote:
>> I am trying to use __sync_fetch_and_add with type ?as "long long" .
>>
>> This gives me the link error :
>> undefined reference to `__sync_fetch_and_add_8'
>>
>> This compiles for a "int " type though. I am using the the gcc option
>> -march=i686
>>
>> Is it possible to do a 64 bit integer operation atomically with the
>> __sync .. builtin functions ?
>
> Works for me:
>
> long long a;
>
> t()
> {
> ?__sync_fetch_and_add(&a, 1);
> }
>
> $ gcc -S t.c -m32 -march=i686 -O2
>
> ? ? ? ?.file ? "t.c"
> ? ? ? ?.text
> ? ? ? ?.p2align 4,,15
> .globl t
> ? ? ? ?.type ? t, @function
> t:
> ? ? ? ?pushl ? %ebp
> ? ? ? ?movl ? ?%esp, %ebp
> ? ? ? ?subl ? ?$12, %esp
> ? ? ? ?movl ? ?%ebx, (%esp)
> ? ? ? ?movl ? ?%esi, 4(%esp)
> ? ? ? ?movl ? ?%edi, 8(%esp)
> ? ? ? ?movl ? ?a, %eax
> ? ? ? ?movl ? ?a+4, %edx
> .L2:
> ? ? ? ?movl ? ?%eax, %esi
> ? ? ? ?movl ? ?%edx, %edi
> ? ? ? ?addl ? ?$1, %esi
> ? ? ? ?adcl ? ?$0, %edi
> ? ? ? ?movl ? ?%esi, %ebx
> ? ? ? ?movl ? ?%edi, %ecx
> ? ? ? ?lock cmpxchg8b ?a
> ? ? ? ?jne ? ? .L2
> ? ? ? ?movl ? ?(%esp), %ebx
> ? ? ? ?movl ? ?4(%esp), %esi
> ? ? ? ?movl ? ?8(%esp), %edi
> ? ? ? ?movl ? ?%ebp, %esp
> ? ? ? ?popl ? ?%ebp
> ? ? ? ?ret
> ? ? ? ?.size ? t, .-t
> ? ? ? ?.comm ? a,8,8
> ? ? ? ?.ident ?"GCC: (GNU) 4.4.3 20100127 (Red Hat 4.4.3-4)"
> ? ? ? ?.section ? ? ? ?.note.GNU-stack,"",@progbits
>
>