On Wed, Aug 19, 2015 at 10:53 AM, H.J. Lu <hjl.to...@gmail.com> wrote:
> On Wed, Aug 19, 2015 at 10:48 AM, Segher Boessenkool
> <seg...@kernel.crashing.org> wrote:
>> On Wed, Aug 19, 2015 at 10:08:01AM -0700, H.J. Lu wrote:
>>> > Maybe something like (heavily cut'n'pasted):
>>> >
>>> >
>>> > @deftypefn {Built-in Function} {void *} __builtin_argument_address (void)
>>> > This function is similar to @code{__builtin_frame_address} with an
>>> > argument of 0, but it returns the address of the incoming arguments to
>>> > the current function rather than the address of its frame.
>>>
>>> This doesn't make senses when there is no argument or arguments
>>> are passed in registers.
>>
>> Sure, but see the weasel-words below ("The exact...")
>>
>>> To me, argument pointer is a virtual concept
>>> and an implementation detail internal to GCC. I am not sure if another
>>> compiler can implement it based on this description.
>>
>> The same is true for frame_address, on many machines.
>
> Stack frame is well understood unlike argument pointer which is
> pretty vague.
>
How about this
@deftypefn {Built-in Function} {void *} __builtin_argument_pointer (void)
This function is similar to @code{__builtin_frame_address} with an
argument of 0, but it returns the address of the incoming arguments to
the current function rather than the address of its frame. Unlike
@code{__builtin_frame_address}, the frame pointer register isn't
required.
The exact definition of this address depends upon the processor and the
calling convention. Usually some arguments are passed in registers and
the rest on the stack, and this builtin returns the address of the
first argument which would be passed on the stack.
@end deftypefn
--
H.J.
