On Mon, Apr 15, 2024 at 02:19:36PM +0200, Jakub Jelinek wrote:
> They weren't the same, one was trying to evaluate the convert_from_reference
> with vc_glvalue, the other evaluates it without that and with vc_prvalue.
> Now, I guess the
> + /* Undo convert_for_arg_passing work here. */
> + if (TYPE_REF_P (TREE_TYPE (x))
> + && !same_type_p (type, TREE_TYPE (TREE_TYPE (x))))
> + x = cp_fold_convert (build_reference_type (type), x);
> part could be thrown away, given the other !same_type_p check (that one is
> needed because adjust_temp_type can't deal with that), at least
> when I remove that
> GXX_TESTSUITE_STDS=98,11,14,17,20,23,26 make check-g++
> RUNTESTFLAGS="dg.exp='constexpr-dtor* pr114426.C constexpr-111284.C
> constexpr-lifetime7.C'"
> still passes.
I've now tested that version and it passed bootstrap/regtest on x86_64-linux
and i686-linux. But as I said earlier, trying to tweak the patch further
doesn't work on the constexpr-dtor{5,6}.C tests.
2024-04-23 Jakub Jelinek <ja...@redhat.com>
PR c++/111284
* constexpr.cc (cxx_bind_parameters_in_call): For PARM_DECLs with
TREE_ADDRESSABLE types use vc_glvalue rather than vc_prvalue for
cxx_eval_constant_expression and if it doesn't have the same
type as it should, cast the reference type to reference to type
before convert_from_reference and instead of adjust_temp_type
take address of the arg, cast to reference to type and then
convert_from_reference.
(cxx_eval_constant_expression) <case PARM_DECL>: For lval case
on parameters with TREE_ADDRESSABLE types lookup result in
ctx->globals if possible. Otherwise if lookup in ctx->globals
was successful for parameter with TREE_ADDRESSABLE type,
recurse with vc_prvalue on the returned value.
* g++.dg/cpp1z/constexpr-111284.C: New test.
* g++.dg/cpp1y/constexpr-lifetime7.C: Expect one error on a different
line.
--- gcc/cp/constexpr.cc.jj 2024-02-13 10:29:57.979155641 +0100
+++ gcc/cp/constexpr.cc 2024-03-07 19:35:01.032412221 +0100
@@ -1877,13 +1877,18 @@ cxx_bind_parameters_in_call (const const
x = build_address (x);
}
if (TREE_ADDRESSABLE (type))
- /* Undo convert_for_arg_passing work here. */
- x = convert_from_reference (x);
- /* Normally we would strip a TARGET_EXPR in an initialization context
- such as this, but here we do the elision differently: we keep the
- TARGET_EXPR, and use its CONSTRUCTOR as the value of the parm. */
- arg = cxx_eval_constant_expression (ctx, x, vc_prvalue,
- non_constant_p, overflow_p);
+ {
+ /* Undo convert_for_arg_passing work here. */
+ x = convert_from_reference (x);
+ arg = cxx_eval_constant_expression (ctx, x, vc_glvalue,
+ non_constant_p, overflow_p);
+ }
+ else
+ /* Normally we would strip a TARGET_EXPR in an initialization context
+ such as this, but here we do the elision differently: we keep the
+ TARGET_EXPR, and use its CONSTRUCTOR as the value of the parm. */
+ arg = cxx_eval_constant_expression (ctx, x, vc_prvalue,
+ non_constant_p, overflow_p);
/* Check we aren't dereferencing a null pointer when calling a non-static
member function, which is undefined behaviour. */
if (i == 0 && DECL_OBJECT_MEMBER_FUNCTION_P (fun)
@@ -1909,7 +1914,16 @@ cxx_bind_parameters_in_call (const const
{
/* Make sure the binding has the same type as the parm. But
only for constant args. */
- if (!TYPE_REF_P (type))
+ if (TREE_ADDRESSABLE (type))
+ {
+ if (!same_type_p (type, TREE_TYPE (arg)))
+ {
+ arg = build_fold_addr_expr (arg);
+ arg = cp_fold_convert (build_reference_type (type), arg);
+ arg = convert_from_reference (arg);
+ }
+ }
+ else if (!TYPE_REF_P (type))
arg = adjust_temp_type (type, arg);
if (!TREE_CONSTANT (arg))
*non_constant_args = true;
@@ -7499,9 +7513,19 @@ cxx_eval_constant_expression (const cons
case PARM_DECL:
if (lval && !TYPE_REF_P (TREE_TYPE (t)))
- /* glvalue use. */;
+ {
+ /* glvalue use. */
+ if (TREE_ADDRESSABLE (TREE_TYPE (t)))
+ if (tree v = ctx->global->get_value (t))
+ r = v;
+ }
else if (tree v = ctx->global->get_value (t))
- r = v;
+ {
+ r = v;
+ if (TREE_ADDRESSABLE (TREE_TYPE (t)))
+ r = cxx_eval_constant_expression (ctx, r, vc_prvalue,
+ non_constant_p, overflow_p);
+ }
else if (lval)
/* Defer in case this is only used for its type. */;
else if (ctx->global->is_outside_lifetime (t))
--- gcc/testsuite/g++.dg/cpp1z/constexpr-111284.C.jj 2024-03-07
16:27:48.113651999 +0100
+++ gcc/testsuite/g++.dg/cpp1z/constexpr-111284.C 2024-03-07
16:26:49.565466606 +0100
@@ -0,0 +1,19 @@
+// PR c++/111284
+// { dg-do compile { target c++17 } }
+
+struct S {
+ S () = default;
+ constexpr S (const S &) noexcept : s{this} {}
+ constexpr S & operator= (const S &) noexcept { return *this; }
+ constexpr bool foo () const noexcept { return s == this; }
+ S *s = this;
+};
+
+constexpr bool
+bar (S x) noexcept
+{
+ return x.foo ();
+}
+
+static_assert (bar (S {}), "");
+static_assert ([] (S x) { return x.foo (); } (S {}), "");
--- gcc/testsuite/g++.dg/cpp1y/constexpr-lifetime7.C.jj 2023-12-13
19:09:33.252657826 +0100
+++ gcc/testsuite/g++.dg/cpp1y/constexpr-lifetime7.C 2024-03-07
19:49:49.342334090 +0100
@@ -87,7 +87,7 @@ constexpr bool n1 = test_access<NonTrivi
constexpr bool n2 = test_modification<NonTrivial>(); // { dg-message "in
.constexpr." "" { target c++20 } }
constexpr bool n3 = test_scope<NonTrivial>(); // { dg-message "in
.constexpr." "" { target c++20 } }
constexpr bool n4 = test_destroy_temp<NonTrivial>(); // { dg-message "in
.constexpr." "" { target c++20 } }
-constexpr bool n5 = test_parameter(NonTrivial{}); // { dg-error
"destroying" "" { target c++20 } }
+constexpr bool n5 = test_parameter(NonTrivial{}); // { dg-message "in
.constexpr." "" { target c++20 } }
constexpr bool n6 = test_bindings<NonTrivial>();
#endif
Jakub
