From: Patrick Palka <ppalka@redhat.com>
To: Patrick Palka <ppalka@redhat.com>
Cc: gcc-patches@gcc.gnu.org, jason@redhat.com
Subject: Re: [PATCH] c++: sizeof(expr) in non-templated requires-expr [PR108563]
Date: Thu, 9 Feb 2023 13:22:35 -0500 (EST) [thread overview]
Message-ID: <54df93ff-b7ff-4e2f-ce94-84643cde01fe@idea> (raw)
In-Reply-To: <20230209181722.3178411-1-ppalka@redhat.com>
On Thu, 9 Feb 2023, Patrick Palka wrote:
> When substituting into sizeof(expr), tsubst_copy_and_build elides
> substitution into the operand if args is NULL_TREE, and instead
> considers the TREE_TYPE of the operand. But here the (templated)
> operand is a TEMPLATE_ID_EXPR with empty TREE_TYPE, so we can't elide
> substitution in this case.
>
> Contrary to the associated comment (dating back to r69130) substituting
> args=NULL_TREE should generally work since we do exactly that in e.g.
> fold_non_dependent_expr, and I don't see why the operand of sizeof would
> be an exception. So this patch just removes this special case.
>
> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> trunk? Diff generated with -w to ignore noisy whitespace changes.
This time with -w actually passed to format-patch:
-- >8 --
PR c++/108563
gcc/cp/ChangeLog:
* pt.cc (tsubst_copy_and_build) <case SIZEOF_EXPR>: Remove
special case for empty args.
gcc/testsuite/ChangeLog:
* g++.dg/cpp2a/concepts-requires35.C: New test.
---
gcc/cp/pt.cc | 11 -----------
gcc/testsuite/g++.dg/cpp2a/concepts-requires35.C | 14 ++++++++++++++
2 files changed, 14 insertions(+), 11 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-requires35.C
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 9f3fc1fa089..f21d28263d1 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -20652,16 +20652,6 @@ tsubst_copy_and_build (tree t,
op1 = TREE_TYPE (op1);
bool std_alignof = (TREE_CODE (t) == ALIGNOF_EXPR
&& ALIGNOF_EXPR_STD_P (t));
- if (!args)
- {
- /* When there are no ARGS, we are trying to evaluate a
- non-dependent expression from the parser. Trying to do
- the substitutions may not work. */
- if (!TYPE_P (op1))
- op1 = TREE_TYPE (op1);
- }
- else
- {
++cp_unevaluated_operand;
++c_inhibit_evaluation_warnings;
if (TYPE_P (op1))
@@ -20670,7 +20660,6 @@ tsubst_copy_and_build (tree t,
op1 = tsubst_copy_and_build (op1, args, complain, in_decl);
--cp_unevaluated_operand;
--c_inhibit_evaluation_warnings;
- }
if (TYPE_P (op1))
r = cxx_sizeof_or_alignof_type (input_location,
op1, TREE_CODE (t), std_alignof,
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-requires35.C b/gcc/testsuite/g++.dg/cpp2a/concepts-requires35.C
new file mode 100644
index 00000000000..2bb4b2b0b5d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-requires35.C
@@ -0,0 +1,14 @@
+// PR c++/108563
+// { dg-do compile { target c++20 } }
+
+template<class T>
+struct foo {
+ static constexpr T value = 0;
+};
+
+template<class T>
+inline constexpr T foo_v = foo<T>::value;
+
+static_assert(requires { sizeof(foo_v<int>); });
+static_assert(requires { requires sizeof(foo_v<int*>) == sizeof(int*); });
+static_assert(requires { requires sizeof(foo_v<char>) == sizeof(char); });
--
2.39.1.418.g7876265d61
next prev parent reply other threads:[~2023-02-09 18:22 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-09 18:17 Patrick Palka
2023-02-09 18:22 ` Patrick Palka [this message]
2023-02-14 23:02 ` Jason Merrill
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