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c++: Fix up instantiation of pointer/reference/array types with attributes [PR119138]

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My r15-7822 PR118787 change unfortunately broke build on x86_64-w64-mingw32.
The reduced testcase below shows what is going on.
va_list on this target is char * with extra (non-dependent) attributes
on it.
Before my r15-7822 change, instantiation of such type used the fast path and
just returned t, but as it has non-NULL TYPE_ATTRIBUTES, it now falls
through, builds a pointer type and then calls
apply_late_template_attributes.  And in there triggers a bug, that function
has been written for types with RECORD_TYPE/UNION_TYPE (or ENUMERAL_TYPE?)
in mind, where we call apply_late_template_attributes with
ATTR_FLAG_TYPE_IN_PLACE and can just apply the non-dependent attributes
directly to TYPE_ATTRIBUTES.  That is wrong for shared types like
{POINTER,REFERENCE,ARRAY}_TYPE etc., we should just force
cp_build_type_attribute_variant to build a variant type for the
non-dependent attributes and then process dependent attributes (which
given attr_flag will DTRT already).

The second change in the patch is an optimization, we can actually return
back to returning t even when TYPE_ATTRIBUTES is non-NULL, as long as it
is non-dependent (dependent attributes are stored first, so it is enough
to check the first attribute).

2025-03-06  Jakub Jelinek  <jakub@redhat.com>

	PR c++/119138
	* pt.cc (apply_late_template_attributes): Set p to NULL if
	ATTR_FLAG_TYPE_IN_PLACE is not set in attr_flags.
	(tsubst) <case POINTER_TYPE, case REFERENCE_TYPE, case ARRAY_TYPE>:
	Reuse original type even if TYPE_ATTRIBUTES is non-NULL, but all
	the attributes are non-dependent.

	* g++.dg/template/pr119138.C: New test.
This commit is contained in:
Jakub Jelinek 2025-03-06 17:58:14 +01:00 • committed by Jakub Jelinek
parent 1ccbf8e2c2
commit 0ba3e5ff14
2 changed files with 22 additions and 3 deletions
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9
gcc/cp/pt.cc
View file

@ -12393,7 +12393,8 @@ apply_late_template_attributes (tree *decl_p, tree attributes, int attr_flags,
to our attributes parameter. */
gcc_assert (*p == attributes);
}
else if (FUNC_OR_METHOD_TYPE_P (*decl_p))
else if (FUNC_OR_METHOD_TYPE_P (*decl_p)
|| (attr_flags & ATTR_FLAG_TYPE_IN_PLACE) == 0)
p = NULL;
else
{
@ -16867,7 +16868,8 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
{
if (type == TREE_TYPE (t)
&& TREE_CODE (type) != METHOD_TYPE
&& TYPE_ATTRIBUTES (t) == NULL_TREE)
&& (TYPE_ATTRIBUTES (t) == NULL_TREE
|| !ATTR_IS_DEPENDENT (TYPE_ATTRIBUTES (t))))
return t;
/* [temp.deduct]
@ -17029,7 +17031,8 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
it will obviously be the same as T. */
if (type == TREE_TYPE (t)
&& domain == TYPE_DOMAIN (t)
&& TYPE_ATTRIBUTES (t) == NULL_TREE)
&& (TYPE_ATTRIBUTES (t) == NULL_TREE
|| !ATTR_IS_DEPENDENT (TYPE_ATTRIBUTES (t))))
return t;
/* These checks should match the ones in create_array_type_for_decl.

16
gcc/testsuite/g++.dg/template/pr119138.C Normal file
View file

@ -0,0 +1,16 @@
// PR c++/119138
// { dg-do compile }
#include <stdarg.h>
template <typename>
void
foo (va_list)
{
}
void
bar (va_list ap)
{
foo <char> (ap);
}