Re: Is a Pointer identical to a Struct { Pointer }?

["M.C.A. (Marco) Devillers" <marco dot devillers at gmail dot com>]

Hmm, no easy fix, heh? What if I would use a signed integer of pointer
size for a character pointer, and just would use the unsigned integers
for passing normal values?

On Wed, Dec 15, 2010 at 4:27 AM, Jay K <jay.krell@cornell.edu> wrote:
> I believe the answer is that it depends on the ABI.
> Some ABIs might sometimes?enregister small structs, making the answer yes.
> Some ABIs might never enregister small structs, making the answer no.
>
> ?- Jay
>
>
>> Date: Wed, 15 Dec 2010 02:58:23 +0100
>> Subject: Is a Pointer identical to a Struct { Pointer }?
>> From: marco.devillers@gmail.com
>> To: libffi-discuss@sourceware.org
>>
>> Hi all,
>>
>> This is a bit of a weird question regarding a quick-and-dirty fix.
>>
>> In my language I use libffi extensively to interface with C. Since I
>> want to support strings in the language I want to discriminate between
>> pointers and pointers to characters in the libffi type information of
>> C functions called.
>>
>> Now one quick-and-dirty hack I came up with is just wrapping a single
>> pointer in a structure as an 'encoding' of a char pointer. That
>> manner, I could discriminate between pointers and 'encoded' pointers
>> to characters easily.Of course, I would like to push values in the
>> normal manner to the C function called.
>>
>> Now that scheme only works if a structure containing one pointer is
>> treated identically to a pointer in most calling conventions of GCC,
>> MVC, etc. on most OSes.
>>
>> Is the latter true. I.e., is the same stack structure build for a
>> pointer, or a structure just holding a pointer? Is there an easier
>> manner to solve this?
>>
>> Any help appreciated,
>> Marco
>