From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by sourceware.org (Postfix) with ESMTPS id 1E3F73858D39 for ; Thu, 9 Feb 2023 00:00:32 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 1E3F73858D39 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1675900831; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=n2d1NnPy6gKyvL0FBjmicQSkNTLT/HguZatfjhoCqCk=; b=MRqXyKnDZIf7QuKo7c9XhWbKq2g9eKDAlI/F9uPyZ3Cn4iO5ExAbIBKfcKldZc1Pr5q+o6 RbskKL4BgL7ek6eVlvjuDR9+DhezzSKcgWOPRaWy4Y/AUXIHyYxsEnK0srJ9gSTqi6NI++ pozhrGmD4XUqfXbiHaDlnKcp7kbg1Og= Received: from mail-qk1-f200.google.com (mail-qk1-f200.google.com [209.85.222.200]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-664-arHLHLAhMWGpGYuEt0VXqw-1; Wed, 08 Feb 2023 19:00:30 -0500 X-MC-Unique: arHLHLAhMWGpGYuEt0VXqw-1 Received: by mail-qk1-f200.google.com with SMTP id j10-20020a05620a288a00b0070630ecfd9bso193279qkp.20 for ; Wed, 08 Feb 2023 16:00:30 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=n2d1NnPy6gKyvL0FBjmicQSkNTLT/HguZatfjhoCqCk=; b=7lYxaF3xTCqhObezc2bavUJa/XR9dY2CXToIY5rClsHjFfADQ8n5ul/DCAbf9A5ZRt msJFdAj9IKcJcL4F3IdpnktehY3kpBUnQgHevfmjzN4hpwX0xi6oxrLvsMhOufEYhYe6 GIKHcHOmP4+2W/IKgSAQwQ5VHC/hTm7qK+XveRcbRGOeazY1YEZthRbAH3d0DXdONEaD wqioe+ZyQGHN0FwGuInuxc3irATmJo83QsAq2VfnCSLkleclK9GQq/KMCsSANSN1/Lra rCWczJpaWEv/PIWIi6VTUDqot8CRpTNBiZcPWDOCSlElRLiqoghn+h8Z9mOnA8WP/FMr FSdg== X-Gm-Message-State: AO0yUKWQ/178Nr53JAy5zFLmoi7I7KhFc3hWDHKVQsRRm47aDDbVpj1R tsJkPExh/zmvXvCS+r6DQ6PfTyAyeh/MpdCVxyKPF3+/nVO5BJF3BS9T0vi5GqJlQfgTNrOADQA x0enmLD1XKNsnzymnMA== X-Received: by 2002:a05:622a:10:b0:3b8:118d:ad86 with SMTP id x16-20020a05622a001000b003b8118dad86mr13845660qtw.21.1675900828706; Wed, 08 Feb 2023 16:00:28 -0800 (PST) X-Google-Smtp-Source: AK7set/2YeAjKHt7f+UavN+eKHEPH/6ErKO0NdNhfPyED8tfSv8N90htxhnYAcZ8+6Q8hGyTjiuSNA== X-Received: by 2002:a05:622a:10:b0:3b8:118d:ad86 with SMTP id x16-20020a05622a001000b003b8118dad86mr13845626qtw.21.1675900828373; Wed, 08 Feb 2023 16:00:28 -0800 (PST) Received: from [172.20.25.72] ([12.198.239.140]) by smtp.gmail.com with ESMTPSA id u1-20020ac83d41000000b003b643951117sm180037qtf.38.2023.02.08.16.00.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 08 Feb 2023 16:00:27 -0800 (PST) Message-ID: <7830a96e-7415-ee72-bbf7-007e5c04b9f1@redhat.com> Date: Wed, 8 Feb 2023 16:00:25 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.6.1 Subject: Re: [PATCH] c++: ICE initing lifetime-extended constexpr var [PR107079] To: Marek Polacek , GCC Patches , Patrick Palka References: <20230208210140.391014-1-polacek@redhat.com> From: Jason Merrill In-Reply-To: <20230208210140.391014-1-polacek@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-12.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,GIT_PATCH_0,KAM_SHORT,NICE_REPLY_A,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On 2/8/23 13:01, Marek Polacek wrote: > (This may not be a complete fix but I got stuck so I'm posting what > I have, which at least fixes the ICE.) > > We ICE on the simple: > > struct X { const X* x = this; }; > constexpr const X& x = X{}; > > where store_init_value initializes 'x' with > > &TARGET_EXPR }> > > but we must lifetime-extend via extend_ref_init_temps and we get > > _ZGR1x_.x = (const struct X *) & >>>;, (const struct X &) &_ZGR1x_; > > Since 'x' was declared constexpr, we do cxx_constant_init and we hit > the preeval code added in r269003 while evaluating the INIT_EXPR: > > _ZGR1x_.x = (const struct X *) & >>> > > but we have no ctx.ctor or ctx.object here so lookup_placeholder won't > find anything that could replace X and we ICE on > 7861 /* A placeholder without a referent. We can get here when > 7862 checking whether NSDMIs are noexcept, or in massage_init_elt; > 7863 just say it's non-constant for now. */ > 7864 gcc_assert (ctx->quiet); > because cxx_constant_init means !ctx->quiet. It's not correct that > there isn't a referent. I think the following patch is a pretty > straightforward fix: pass the _ZGR var down to maybe_constant_init so > that it can replace the PLACEHOLDER_EXPR with _ZGR1x_. > > What I wasn't able to make work is the commented assert in the test. > It doesn't pass because we complain that _ZGR1x_ isn't a constexpr > variable, That sounds like we aren't (correctly) implementing https://eel.is/c++draft/expr.const#4.7 > but making it so would just result in "used in its own > initializer" (which is true). True, but not in the sense it means; its initializer doesn't depend on its (uninitialized) value. > I notice that while clang++ compiles > the assert fine, MSVC++/icc reject it as non-constant. So maybe we > don't have to/shouldn't make it work. > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? > > PR c++/107079 > > gcc/cp/ChangeLog: > > * call.cc (set_up_extended_ref_temp): Pass var to maybe_constant_init. > > gcc/testsuite/ChangeLog: > > * g++.dg/cpp0x/constexpr-nsdmi2.C: New test. > --- > gcc/cp/call.cc | 2 +- > gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C | 9 +++++++++ > 2 files changed, 10 insertions(+), 1 deletion(-) > create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C > > diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc > index f7c5d9da94b..a0afab9b26a 100644 > --- a/gcc/cp/call.cc > +++ b/gcc/cp/call.cc > @@ -13583,7 +13583,7 @@ set_up_extended_ref_temp (tree decl, tree expr, vec **cleanups, > > /* If the initializer is constant, put it in DECL_INITIAL so we get > static initialization and use in constant expressions. */ > - init = maybe_constant_init (expr); > + init = maybe_constant_init (expr, var); We should also pass true for manifestly_const_eval as in store_init_value. > /* As in store_init_value. */ > init = cp_fully_fold (init); > if (TREE_CONSTANT (init)) > diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C > new file mode 100644 > index 00000000000..6dbb7eb739a > --- /dev/null > +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-nsdmi2.C > @@ -0,0 +1,9 @@ > +// PR c++/107079 > +// { dg-do compile { target c++11 } } > + > +struct X { > + const X* x = this; > +}; > +constexpr const X& x = X{}; > +// TODO: Should the assert pass? > +//static_assert(x.x == &x); > > base-commit: 77bb54b1b07add45007c664724b726541d672ef3