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backport: re PR c++/92695 (P1064R0 - virtual constexpr fails if object taken from array)

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Backported from mainline
	2019-12-03  Jakub Jelinek  <jakub@redhat.com>

	PR c++/92695
	* constexpr.c (cxx_bind_parameters_in_call): For virtual calls,
	adjust the first argument to point to the derived object rather
	than its base.

	* g++.dg/cpp2a/constexpr-virtual14.C: New test.

From-SVN: r279664
This commit is contained in:
Jakub Jelinek 2019-12-20 18:33:13 +01:00 committed by Jakub Jelinek
parent d9c7be4ce3
commit ae1b211b58
4 changed files with 61 additions and 0 deletions
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7
gcc/cp/ChangeLog
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@ -1,6 +1,13 @@
2019-12-20 Jakub Jelinek <jakub@redhat.com>
Backported from mainline
2019-12-03 Jakub Jelinek <jakub@redhat.com>
PR c++/92695
* constexpr.c (cxx_bind_parameters_in_call): For virtual calls,
adjust the first argument to point to the derived object rather
than its base.
2019-12-02 Jakub Jelinek <jakub@redhat.com>
PR c++/92695

22
gcc/cp/constexpr.c
View File

@ -1419,6 +1419,28 @@ cxx_bind_parameters_in_call (const constexpr_ctx *ctx, tree t,
arg = adjust_temp_type (type, arg);
if (!TREE_CONSTANT (arg))
*non_constant_args = true;
/* For virtual calls, adjust the this argument, so that it is
the object on which the method is called, rather than
one of its bases. */
if (i == 0 && DECL_VIRTUAL_P (fun))
{
tree addr = arg;
STRIP_NOPS (addr);
if (TREE_CODE (addr) == ADDR_EXPR)
{
tree obj = TREE_OPERAND (addr, 0);
while (TREE_CODE (obj) == COMPONENT_REF
&& DECL_FIELD_IS_BASE (TREE_OPERAND (obj, 1))
&& !same_type_ignoring_top_level_qualifiers_p
(TREE_TYPE (obj), DECL_CONTEXT (fun)))
obj = TREE_OPERAND (obj, 0);
if (obj != TREE_OPERAND (addr, 0))
arg = build_fold_addr_expr_with_type (obj,
TREE_TYPE (arg));
}
}
*p = build_tree_list (parms, arg);
p = &TREE_CHAIN (*p);
}

5
gcc/testsuite/ChangeLog
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@ -1,6 +1,11 @@
2019-12-20 Jakub Jelinek <jakub@redhat.com>
Backported from mainline
2019-12-03 Jakub Jelinek <jakub@redhat.com>
PR c++/92695
* g++.dg/cpp2a/constexpr-virtual14.C: New test.
2019-12-02 Jakub Jelinek <jakub@redhat.com>
PR c++/92695

27
gcc/testsuite/g++.dg/cpp2a/constexpr-virtual14.C Normal file
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@ -0,0 +1,27 @@
// PR c++/92695
// { dg-do compile { target c++2a } }
struct A {
virtual int get () = 0;
virtual int set (A *o) = 0;
};
struct B : A {
constexpr int get () override { return 10; }
constexpr int set (A *o) override { a = o; return 20; }
A *a {};
};
constexpr auto addressof = [] (A &n) { return &n; };
struct C {
B b;
A *c { addressof (b) };
constexpr int add () { return c->set (addressof (b)); }
};
struct D {
B b[2];
A *c { addressof (b[0]) };
constexpr int add () { return c->set (addressof (b[0])); }
};
template <typename T>
constexpr int get () { T f; return f.add (); }
static_assert (get<C> () == 20);
static_assert (get<D> () == 20);