From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
	id CE907382FAE9; Thu, 24 Nov 2022 18:49:11 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org CE907382FAE9
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1669315751;
	bh=bS7C4Kq2++enbp2LLzdFbhdTmMIuwbWO7oJfWWB8HLw=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=xn5YjJ/mDmqMA6giDRlJ9b3GqWWY36OKG5INeD9l629/LASVTCl1RxOHPSsWmioRG
	 qYo0XBnZvnSD62Cse6qjBi4O2iqgwOVUgqQi7TsxsxmtYrTekdB1lJ3kv0zYhe9Oit
	 hZQZtoU/nInKxoU4yTorek9wZXf6Gpeu91MJqlyM=
From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/107862] Returning an std::vector from a lambda fails to be
 constexpr, while a custom class with allocated storage works
Date: Thu, 24 Nov 2022 18:49:11 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
X-Bugzilla-Version: 12.2.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: pinskia at gcc dot gnu.org
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-107862-4-aIetZjZVW2@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-107862-4@http.gcc.gnu.org/bugzilla/>
References: <bug-107862-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
List-Id: <gcc-bugs.sourceware.org>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107862

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I don't think this is valid code.
In the function dynamic_data_to_array you have:
    std::array<VT, test.size()> data;

But test.size() is not a constexpr unless test is a constexpr. making test a
constexpr does not work as it has dynamic allocation

In your Test struct you have:
    constexpr unsigned size() const { return 1; }

So it is always a constexpr ...

Note clang also rejects this code for the same reason as GCC even with libc=
++.=