> On 27 May 2026, at 22:03, H.J. Lu <[email protected]> wrote:
>
> On Thu, May 28, 2026 at 4:16 AM Jason Merrill <[email protected]> wrote:
>>
>> On 5/8/26 6:05 AM, H.J. Lu wrote:
>>> default_stack_protect_guard calls
>>>
>>> lang_hooks.types.type_for_mode (ptr_mode, 1);
>>>
>>> to get an integer type for __stack_chk_guard which is declared as a
>>> global symbol of type uintptr_t. For 32-bit systems, uintptr_t may
>>> be either unsigned int or unsigned long int. On 32-bit Darwin, we get
>>>
>>> $ cat /tmp/x.c
>>> __UINTPTR_TYPE__ __stack_chk_guard = 0x1000;
>>> $ ./xgcc -B./ -S /tmp/x.c -m32
>>> /tmp/x.c:1:18: error: conflicting types for ‘__stack_chk_guard’; have
>>> ‘long unsigned int’
>>> 1 | __UINTPTR_TYPE__ __stack_chk_guard = 0x1000;
>>> | ^~~~~~~~~~~~~~~~~
>>> cc1: note: previous declaration of ‘__stack_chk_guard’ with type ‘unsigned
>>> int’
>>> $
>>>
>>> since lang_hooks.types.type_for_mode returns unsigned int while Darwin's
>>> uintptr_t is unsigned long int.
>>>
>>> Add LANG_HOOKS_TYPE_FOR_MODE_KIND to specify signed or unsigned integer
>>> type for pointer and update default_stack_protect_guard to call
>>>
>>> lang_hooks.types.type_for_mode_kind
>>> (ptr_mode, 1, KIND_IS_INTEGER_FOR_POINTER);
>>>
>>> to get unsigned integer type for pointer.
>>
>> Instead of adding this additional parameter; can we just adjust the
>> existing c_common_type_for_mode handling of pointer modes, i.e.
>>
>>> if (mode == TYPE_MODE (build_pointer_type (char_type_node))
>>> || mode == TYPE_MODE (build_pointer_type (integer_type_node)))
>>> {
>>> unsigned int precision
>>> = GET_MODE_PRECISION (as_a <scalar_int_mode> (mode));
>>> return (unsignedp
>>> ? make_unsigned_type (precision)
>>> : make_signed_type (precision));
>>> }
>>
>> to return [u]intptr_type_node?
>>
>> Jason
>>
>
> This:
>
> diff --git a/gcc/c-family/c-common.cc b/gcc/c-family/c-common.cc
> index ac9c681d4b8..992e279f332 100644
> --- a/gcc/c-family/c-common.cc
> +++ b/gcc/c-family/c-common.cc
> @@ -2455,6 +2455,9 @@ c_common_type_for_mode (machine_mode mode, int
> unsignedp)
> tree t;
> int i;
>
> + if (mode == TYPE_MODE (intptr_type_node))
> + return unsignedp ? uintptr_type_node : intptr_type_node;
> +
> if (mode == TYPE_MODE (integer_type_node))
> return unsignedp ? unsigned_type_node : integer_type_node;
>
> works for
>
> __UINTPTR_TYPE__ __stack_chk_guard = 0x1000;
>
> on Darwin. But I don't know if it will cause other issues for Darwin.
I very much doubt that the issues are confined to Darwin (it just happens to be
one of the earlier-tested non-linux platforms), what’s needed is something
generic
that works by construction.
Do you have a composite complete proposed patch?; I can certainly test such
a patch on affected darwin versions - but comment above remains.
Iain
>
> --
> H.J.
