On Mon, Jan 26, 2026 at 8:49 PM Jason Merrill <[email protected]> wrote:
>
> On 12/14/25 8:10 AM, H.J. Lu wrote:
> > On Sat, Dec 13, 2025 at 5:33 PM Stefan Schulze Frielinghaus
> > <[email protected]> wrote:
> >>
> >> On Sun, Oct 26, 2025 at 10:29:30AM +0800, H.J. Lu wrote:
> >>> On Sat, Oct 25, 2025 at 4:42 PM H.J. Lu <[email protected]> wrote:
> >>> ...
> >>>> Here is the v4 patch.
> >>>>
> >>>> Add a new target hook, stack_protect_guard_symbol, to support the user
> >>>> provided stack protection guard as an internal symbol. If the hook is
> >>>> true,
> >>>>
> >>>> 1. Make __stack_chk_guard an internal C/C++ symbol.
> >>>> 2. Declare __stack_chk_guard as a size_t variable if size_t has the same
> >>>> size as pointer so that it can be initialized as an integer.
> >>>> 3. If the user declared variable matches __stack_chk_guard, merge it
> >>>> with __stack_chk_guard, including its visibility attribute.
> >>>> 4. Define the __stack_protection_guard_is_internal_symbol__ macro to
> >>>> indicate that __stack_chk_guard is an internal symbol.
> >>>>
> >>>> gcc/
> >>>>
> >>>> PR c/121911
> >>>> * target.def (stack_protect_guard_symbol): New target hook.
> >>>> * targhooks.cc (default_stack_protect_guard): If
> >>>> targetm.stack_protect_guard_symbol is true, make it an internal
> >>>> symbol and use size_type_node if it has the same size as
> >>>> ptr_type_node.
> >>>> * tree.cc (build_common_tree_nodes): If stack protector is
> >>>> enabled and targetm.stack_protect_guard_symbol is true, call
> >>>> targetm.stack_protect_guard.
> >>>> * config/i386/i386.cc (TARGET_STACK_PROTECT_GUARD_SYMBOL): New.
> >>>> * doc/tm.texi: Regenerated.
> >>>> * doc/tm.texi.in (TARGET_STACK_PROTECT_GUARD_SYMBOL): New.
> >>>>
> >>>> gcc/c-family/
> >>>>
> >>>> PR c/121911
> >>>> * c-common.cc (matching_stack_protect_guard_decl_p): New.
> >>>> * c-common.h (matching_stack_protect_guard_decl_p): Likewise.
> >>>> * c-cppbuiltin.cc (c_cpp_builtins): Define the
> >>>> __stack_protection_guard_is_internal_symbol__ macro if
> >>>> targetm.stack_protect_guard_symbol is true.
> >>>>
> >>>> gcc/c/
> >>>>
> >>>> PR c/121911
> >>>> * c-decl.cc: Include "c-family/c-common.h".
> >>>> (merge_decls): Add a bool argument to keep the old type and copy
> >>>> the old type if true.
> >>>> (duplicate_decls): If the old decl is the stack protect guard and
> >>>> the new decl matches the old decl, keep the type of the old decl.
> >>>>
> >>>> gcc/cp/
> >>>>
> >>>> PR c/121911
> >>>> * decl.cc: Include "c-family/c-common.h".
> >>>> (duplicate_decls): 2 types match if the old decl is the stack
> >>>> protect guard and the new decl matches the old decl.
> >>>>
> >>>> gcc/testsuite/
> >>>>
> >>>> PR c/121911
> >>>> * g++.target/i386/ssp-global-1.C: New test.
> >>>> * g++.target/i386/ssp-global-2.C: Likewise.
> >>>> * g++.target/i386/ssp-global-3.C: Likewise.
> >>>> * g++.target/i386/ssp-global-4.C: Likewise.
> >>>> * g++.target/i386/ssp-global-hidden-1.C: Likewise.
> >>>> * g++.target/i386/ssp-global-hidden-2.C: Likewise.
> >>>> * g++.target/i386/ssp-global-hidden-3.C: Likewise.
> >>>> * gcc.target/i386/ssp-global-2.c: Likewise.
> >>>> * gcc.target/i386/ssp-global-3.c: Likewise.
> >>>> * gcc.target/i386/ssp-global-4.c: Likewise.
> >>>> * gcc.target/i386/ssp-global-hidden-1.c: Likewise.
> >>>> * gcc.target/i386/ssp-global-hidden-2.c: Likewise.
> >>>> * gcc.target/i386/ssp-global-hidden-3.c: Likewise.
> >>>>
> >>>
> >>> Here is the v5 patch. The main difference is that __stack_chk_guard
> >>> is an internal symbol with C linkage now.
> >>>
> >
> > Here is the v6 patch to rename the target hook, stack_protect_guard_symbol,
> > to stack_protect_guard_symbol_p.
> >
> > Add a new target hook, stack_protect_guard_symbol_p, to support the user
> > provided stack protection guard as an internal symbol. If the hook
> > returns true,
> >
> > 1. Make __stack_chk_guard an internal C/C++ symbol.
> > 2. Declare __stack_chk_guard as a size_t variable if size_t has the same
> > size as pointer so that it can be initialized as an integer.
> > 3. If the user declared variable matches __stack_chk_guard, merge it
> > with __stack_chk_guard, including its visibility attribute.
> > 4. Define the __stack_protection_guard_is_internal_symbol__ macro to
> > indicate that __stack_chk_guard is an internal symbol.
> >
> > gcc/
> >
> > PR c/121911
> > * target.def (stack_protect_guard_symbol_p): New target hook.
> > * targhooks.cc (default_stack_protect_guard): If the
> > stack_protect_guard_symbol_p hook returns true, use size_type_node
> > if it has the same size as ptr_type_node.
> > * config/i386/i386.cc (ix86_stack_protect_guard_symbol_p): New.
> > (TARGET_STACK_PROTECT_GUARD_SYMBOL_P): Likewise.
> > * doc/tm.texi: Regenerated.
> > * doc/tm.texi.in (TARGET_STACK_PROTECT_GUARD_SYMBOL_P): New.
> >
> > gcc/c-family/
> >
> > PR c/121911
> > * c-common.cc (stack_protect_guard_decl): New.
> > (pushing_stack_protect_guard_decl): Likewise.
> > (c_stack_protect_guard_decl_p): Likewise.
> > (duplicate_stack_protect_guard_decl_p): Likewise.
> > (c_common_nodes_and_builtins): If the stack_protect_guard_symbol_p
> > hook returns true, call targetm.stack_protect_guard.
> > * c-common.h (c_stack_protect_guard_decl_p): New.
> > (duplicate_stack_protect_guard_decl_p): Likewise.
> > * c-cppbuiltin.cc (c_cpp_builtins): Define the
> > __stack_protection_guard_is_internal_symbol__ macro if the
> > stack_protect_guard_symbol_p hook returns.
> >
> > gcc/c/
> >
> > PR c/121911
> > * c-decl.cc: Include "c-family/c-common.h".
> > (merge_decls): Add a bool argument to keep the old type and copy
> > the old type if true.
> > (duplicate_decls): If the old decl is the stack protect guard and
> > the new decl matches the old decl, keep the type of the old decl.
> >
> > gcc/cp/
> >
> > PR c/121911
> > * cp-objcp-common.cc (cp_pushdecl): Change the stack protection
> > guard symbol to C linkage.
> > * decl.cc: Include "c-family/c-common.h".
> > (duplicate_decls): 2 types match if the old decl is the stack
> > protect guard and the new decl matches the old decl.
> >
> > gcc/testsuite/
> >
> > PR c/121911
> > * g++.target/i386/ssp-global-1.C: New test.
> > * g++.target/i386/ssp-global-2.C: Likewise.
> > * g++.target/i386/ssp-global-3.C: Likewise.
> > * g++.target/i386/ssp-global-4.C: Likewise.
> > * g++.target/i386/ssp-global-hidden-1.C: Likewise.
> > * g++.target/i386/ssp-global-hidden-2.C: Likewise.
> > * g++.target/i386/ssp-global-hidden-3.C: Likewise.
> > * gcc.target/i386/ssp-global-2.c: Likewise.
> > * gcc.target/i386/ssp-global-3.c: Likewise.
> > * gcc.target/i386/ssp-global-4.c: Likewise.
> > * gcc.target/i386/ssp-global-hidden-1.c: Likewise.
> > * gcc.target/i386/ssp-global-hidden-2.c: Likewise.
> > * gcc.target/i386/ssp-global-hidden-3.c: Likewise.
>
> > +/* The stack protection guard. */
> > +static tree stack_protect_guard_decl;
>
> I don't see why we need a local copy of targetm.stack_protect_guard()?
I will drop it.
> > +/* True if the stack protection guard is being pushed. */
> > +static bool pushing_stack_protect_guard_decl;
>
> ...or a flag in addition to comparing with stack_protect_guard().
>
> It seems like a lot of the complication of this patch is to allow
> declarations with a different type, contrary to every other declaration.
> This is quite novel, and it's not clear
bool
duplicate_stack_protect_guard_decl_p (tree newdecl, tree olddecl)
{
if (newdecl != error_mark_node
&& c_stack_protect_guard_decl_p (olddecl))
{
/* Allow different integer types with the same size. */
tree oldtype = TREE_TYPE (olddecl);
tree newtype = TREE_TYPE (newdecl);
if (TYPE_CANONICAL (newtype) == TYPE_CANONICAL (oldtype)
|| (TREE_CODE (newtype) == INTEGER_TYPE
&& TREE_CODE (oldtype) == INTEGER_TYPE
&& (TYPE_PRECISION (newtype)
== TYPE_PRECISION (oldtype))))
return true;
}
return false;
}
is to allow
const unsigned long int __stack_chk_guard;
unsigned long int __stack_chk_guard;
and
const unsigned int __stack_chk_guard;
unsigned long int __stack_chk_guard;
> to me what the motivation is.
> Why can't we just say it needs to be uintptr_t?
uintptr_type_node isn't available in targhooks.cc. Can I use
size_type_node instead?
> Jason
>
--
H.J.
