From patchwork Thu Aug 22 23:36:12 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Simon Marchi X-Patchwork-Id: 34253 Received: (qmail 77608 invoked by alias); 22 Aug 2019 23:36:26 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Delivered-To: mailing list gdb-patches@sourceware.org Received: (qmail 77597 invoked by uid 89); 22 Aug 2019 23:36:26 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-14.4 required=5.0 tests=AWL, BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, KAM_SHORT, SPF_HELO_PASS, SPF_PASS autolearn=ham version=3.3.1 spammy=chances, HTo:U*palves, wondered, 1_57_0 X-HELO: smtp.polymtl.ca Received: from smtp.polymtl.ca (HELO smtp.polymtl.ca) (132.207.4.11) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Thu, 22 Aug 2019 23:36:24 +0000 Received: from simark.ca (simark.ca [158.69.221.121]) (authenticated bits=0) by smtp.polymtl.ca (8.14.7/8.14.7) with ESMTP id x7MNaE2e006181 (version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 22 Aug 2019 19:36:19 -0400 DKIM-Filter: OpenDKIM Filter v2.11.0 smtp.polymtl.ca x7MNaE2e006181 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=polymtl.ca; s=default; t=1566516980; bh=oOV7sGTAjNBkuhaWIFNBgBnBRsdFAcpji44mrM0mZr8=; h=Subject:From:To:References:Date:In-Reply-To:From; b=LQPiDAPHzyzxLzSBnwFIJzaHBuUaDy5o1SIqMuJcSGj75oDbxawOJ5HqI7vkTjQJP LkwwL2Urc0ixtXqISxEgRuDbAttr3FiknWNYOJz2Nh5Cw29nmsC9BKN9tiZMHcg/fA qW3+ILiMbZwx+/BAkdUgp4wjEHBpJpzHAKvyRzmU= Received: from [172.16.2.176] (wsip-184-188-36-2.sd.sd.cox.net [184.188.36.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by simark.ca (Postfix) with ESMTPSA id A45271E636; Thu, 22 Aug 2019 19:36:13 -0400 (EDT) Subject: Re: [PATCH] Remove some variables in favor of using gdb::optional From: Simon Marchi To: Pedro Alves , gdb-patches@sourceware.org References: <20190804201023.25628-1-simon.marchi@polymtl.ca> <9b1cdf6d-baae-3a5e-c2ea-fcdf124b7a1b@redhat.com> <65a23d93-bf2e-de1a-9052-f6d75832c2a1@polymtl.ca> Message-ID: <697c3e3d-4f75-4fb2-685b-a6fa59c7a2a3@polymtl.ca> Date: Thu, 22 Aug 2019 19:36:12 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <65a23d93-bf2e-de1a-9052-f6d75832c2a1@polymtl.ca> X-IsSubscribed: yes On 2019-08-21 8:44 p.m., Simon Marchi wrote: > On 2019-08-21 3:38 p.m., Pedro Alves wrote: >> std::optional is evil. :-) >> >> E.g. it's very easy to write (or miss converting) >> >> if (is_static) >> >> and not realize that that is doing the wrong thing. >> >> https://www.boost.org/doc/libs/1_57_0/libs/optional/doc/html/boost_optional/tutorial/a_note_about_optional_bool_.html >> >> Not saying to change the code (*), but seeing it gives me the creeps, so I couldn't resist. :-) >> >> * - a yes/no/unknown tristate type a-la boost::tribool would be nice >> to have, IMO. It could be used more clearly in these situations >> and could supersede auto_boolean. >> >> Thanks, >> Pedro Alves > > Oh, thanks for pointing out. I had never realized this but it makes sense. There should be a compiler > warning about it! Or maybe it would belong to a linter. > > I'll look into adding a tristate bool and fixing it. > > Simon > I started looking into it, seeing if I could implement something like boost's tribool, but then wondered, why don't we use boost directly? Its license is compatible with the GPL [1], which from what I understand means that it can be used to build a GPL program. [1] https://www.gnu.org/licenses/license-list.html#boost Boost is very widely available, so I'd prefer if we could depend on the system-installed boost, or have the user provide it, but I would understand if others didn't want to add that burden to those who build GDB. So an alternative would be to carry a version of boost (maybe just the files that we need) in our repo. This would have the advantage that everybody would build with the same version, hence less chances of build failures with particular combinations of compilers and boost versions, or using features from a too recent boost. What do you think? Here's what a patch to remove the gdb::optional would look like if we used boost:tribool: From 440b941b9b839943ccabf90c6370450580e92700 Mon Sep 17 00:00:00 2001 From: Simon Marchi Date: Thu, 22 Aug 2019 19:13:13 -0400 Subject: [PATCH] gdb: Use boost:tribool for is_static in dw2_debug_names_iterator::next --- gdb/dwarf2read.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c index de9755f6ce30..915e0b25cea1 100644 --- a/gdb/dwarf2read.c +++ b/gdb/dwarf2read.c @@ -90,6 +90,7 @@ #include #include "rust-lang.h" #include "gdbsupport/pathstuff.h" +#include /* When == 1, print basic high level tracing messages. When > 1, be more verbose. @@ -5843,7 +5844,7 @@ dw2_debug_names_iterator::next () return NULL; } const mapped_debug_names::index_val &indexval = indexval_it->second; - gdb::optional is_static; + boost::tribool is_static(boost::indeterminate); dwarf2_per_cu_data *per_cu = NULL; for (const mapped_debug_names::index_val::attr &attr : indexval.attr_vec) { @@ -5910,10 +5911,10 @@ dw2_debug_names_iterator::next () goto again; /* Check static vs global. */ - if (is_static.has_value () && m_block_index.has_value ()) + if (!boost::indeterminate(is_static) && m_block_index.has_value ()) { const bool want_static = *m_block_index == STATIC_BLOCK; - if (want_static != *is_static) + if (want_static != is_static) goto again; }