On Mon, May 11, 2026 at 4:49 PM Iain Sandoe <[email protected]> wrote:
>
> Hi HJ
>
> > On 8 May 2026, at 11:05, H.J. Lu <[email protected]> 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
>
> FWIW, I suspect that, at the very least, Windows does the same.
>
> > $ 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.
>
> OK. So this does fix bootstrap on Darwin platform versions with 32b
> mulitilibs (and
> 32b hosts). However there is still work to do on the testcases (ABI-related
> differences
> at least).
>
> It seems rather excessive to need to add two target hooks for this small
> feature.
>
> We have C++ - could you not add a defaulted parameter to the original hook
> that
> would allow for querying a specific result for the mode type without needing
> to
> churn the code for every other use?
The default function parameter doesn't work on function pointers:
[hjl@gnu-tgl-3 tmp]$ cat x.cc
void (*foo) (int = 0);
[hjl@gnu-tgl-3 tmp]$ gcc -S x.cc
x.cc:1:18: error: default arguments are only permitted for function
parameters [-fpermissive]
1 | void (*foo) (int = 0);
| ^
[hjl@gnu-tgl-3 tmp]$
> thanks
> Iain
>
> >
> > gcc/
> >
> > PR c/125226
> > * langhooks-def.h (LANG_HOOKS_TYPE_FOR_MODE_KIND): New.
> > (LANG_HOOKS_FOR_TYPES_INITIALIZER): Add
> > LANG_HOOKS_TYPE_FOR_MODE_KIND.
> > * langhooks.h (type_kind): New enum.
> > (lang_hooks_for_types): Add type_for_mode_kind.
> > * targhooks.c (default_stack_protect_guard): Call
> > lang_hooks.types.type_for_mode_kind if not NULL.
> >
> > gcc/c-family/
> >
> > PR c/125226
> > * c-common.cc (c_common_type_for_mode): Renamed to ...
> > (c_common_type_for_mode_kind): This. Add an argument for type
> > kind. Return intptr_type_node/uintptr_type_node when asking
> > for integer type for pointers.
> > (c_common_type_for_mode): New. Call c_common_type_for_mode_kind
> > with KIND_IS_UNKNOWN.
> > * c-common.h: Include "langhooks.h".
> > (c_common_type_for_mode_kind): New prototype.
> > * c-objc-common.h (LANG_HOOKS_TYPE_FOR_MODE_KIND): New.
> >
> > gcc/cp/
> >
> > PR c/125226
> > * cp-objcp-common.h (LANG_HOOKS_TYPE_FOR_MODE_KIND): New.
>
>
> >
> >
> > --
> > H.J.
> > <0001-c-c-Get-unsigned-integer-type-for-pointer.patch>
>
--
H.J.
