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c++: ICE with concepts TS multiple auto deduction [PR101886]

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In extract_autos_r, we need to recompute TYPE_CANONICAL for the template
type parameter after adjusting its index, otherwise we end up with a
comptypes ICE for the below testcase.  Note that such in-place type
adjustment isn't generally safe to do since the type could be the
TYPE_CANONICAL of another (unadjusted) type, but in this case the
canonical auto (of some level and 0 index) is the first auto (of that
level) that's created, and so any auto that we do end up adjusting can't
be the canonical one.

	PR c++/101886

gcc/cp/ChangeLog:

	* pt.cc (extract_autos_r): Recompute TYPE_CANONICAL after
	adjusting the template type parameter's index.  Simplify
	by using TEMPLATE_TYPE_IDX.  Add some sanity checks.

gcc/testsuite/ChangeLog:

	* g++.dg/concepts/auto5.C: New test.
This commit is contained in:
Patrick Palka 2022-12-19 14:59:43 -05:00
parent a39f454f0f
commit a7c8036b26
2 changed files with 18 additions and 3 deletions
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12
gcc/cp/pt.cc
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@ -29243,18 +29243,24 @@ extract_autos_r (tree t, void *data)
{
/* All the autos were built with index 0; fix that up now. */
tree *p = hash.find_slot (t, INSERT);
unsigned idx;
int idx;
if (*p)
/* If this is a repeated constrained-type-specifier, use the index we
chose before. */
idx = TEMPLATE_PARM_IDX (TEMPLATE_TYPE_PARM_INDEX (*p));
idx = TEMPLATE_TYPE_IDX (*p);
else
{
/* Otherwise this is new, so use the current count. */
*p = t;
idx = hash.elements () - 1;
}
TEMPLATE_PARM_IDX (TEMPLATE_TYPE_PARM_INDEX (t)) = idx;
if (idx != TEMPLATE_TYPE_IDX (t))
{
gcc_checking_assert (TEMPLATE_TYPE_IDX (t) == 0);
gcc_checking_assert (TYPE_CANONICAL (t) != t);
TEMPLATE_TYPE_IDX (t) = idx;
TYPE_CANONICAL (t) = canonical_type_parameter (t);
}
}
/* Always keep walking. */

9
gcc/testsuite/g++.dg/concepts/auto5.C Normal file
View file

@ -0,0 +1,9 @@
// PR c++/101886
// { dg-do compile { target c++17_only } }
// { dg-options "-fconcepts-ts" }
template<typename...> struct A { };
A<int, int> a;
A<auto, auto> b1 = a;
A<auto, auto> b2 = a;