From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr1-f50.google.com (mail-wr1-f50.google.com [209.85.221.50]) by sourceware.org (Postfix) with ESMTPS id 3862F3857806 for ; Wed, 16 Mar 2022 13:26:16 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 3862F3857806 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=palves.net Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-wr1-f50.google.com with SMTP id h15so2975370wrc.6 for ; Wed, 16 Mar 2022 06:26:16 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:references:from:in-reply-to :content-transfer-encoding; bh=/U45GIJinp/39NGcRKbf+/4oPKX9D+uegtUeR06qVCQ=; b=k5dlbCaKh9zUEdevyBVISmwtHdSbC4G1FX8tupKJhkOPMicrUP6MFe69zU2r1QqFzk Dpx0efw2yhs7iyu6FIZl7RGO/E9GP82ubebik4QDwltqZz8cKjjlUwhDst9mlRSmfzUP 85DYS09WV9kKw7DKFK5d53VMrSm21EPkL7emo7TCXpWv+jeTibGo4DfIHklunWTQT/CP h0i7Tz4r16Snt2CItVQXKWClBbhhm3Gs0wtUoCUwu0IVwdsHwLIo5Pn++Hfix5MZwRAz tujnMsWZzAy+AAH5dRE2mg4exIH31JXcjweJ2vG6sCUgW163Z59SVxNeWfsmqAonGLfv hs9Q== X-Gm-Message-State: AOAM531AkGQHJngPQ3D2AfET1HeZLNjqkHu8fL7H/quhvRfVAXw7CuRX n20rQUZrBS/RUU4jzM+lJZE= X-Google-Smtp-Source: ABdhPJzCz9BY67m3TRv432M7/ARh/pVy0wxbE1bkrlgYQIXo/hPO7qAwbTWbLgd1V+AP+jr3YihuWg== X-Received: by 2002:a05:6000:15cb:b0:203:d94c:d764 with SMTP id y11-20020a05600015cb00b00203d94cd764mr16792wry.210.1647437175041; Wed, 16 Mar 2022 06:26:15 -0700 (PDT) Received: from ?IPV6:2001:8a0:f924:2600:209d:85e2:409e:8726? ([2001:8a0:f924:2600:209d:85e2:409e:8726]) by smtp.gmail.com with ESMTPSA id j34-20020a05600c1c2200b0038995cb915fsm8230410wms.9.2022.03.16.06.26.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 16 Mar 2022 06:26:13 -0700 (PDT) Message-ID: <410969bd-7d08-f81d-638a-39dde9ff4fd4@palves.net> Date: Wed, 16 Mar 2022 13:26:12 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Subject: Re: [PATCH 4/4] gdb: make internalvar use a variant Content-Language: en-US To: Simon Marchi , Tom Tromey , Simon Marchi via Gdb-patches References: <20220201140717.3046952-1-simon.marchi@polymtl.ca> <20220201140717.3046952-5-simon.marchi@polymtl.ca> <87bkylu1ow.fsf@tromey.com> <205f0a37-e832-2e25-32b6-266acc33753d@palves.net> <81442d2a-055a-961a-c804-ed743bc04c72@polymtl.ca> From: Pedro Alves In-Reply-To: <81442d2a-055a-961a-c804-ed743bc04c72@polymtl.ca> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-3.7 required=5.0 tests=BAYES_00, FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS, KAM_DMARC_STATUS, NICE_REPLY_A, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE autolearn=no autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 16 Mar 2022 13:26:17 -0000 On 2022-03-16 02:06, Simon Marchi wrote: > With std: > > > $1 = { > next = 0x60600000ff20, > name = 0x602000085350 "salut", > v = std::variant [index 0] = {{}} > } > >> AFAICT from variant.cpp source file, the variant storage is an untyped buffer: >> >> enum { data_align = detail::typelist_max_alignof< variant_types >::value }; >> >> using aligned_storage_t = typename std::aligned_storage< data_size, data_align >::type; >> aligned_storage_t data; >> >> so I guess printing a nonstd::variant results in pretty opaque output. We'd need a pretty >> printer to fix this. Or maybe we just assume that people developing/debugging GDB build >> it against a C++17 or higher compiler? (Not sure that's a great assumption.) > > Do you know off-hand if the std::variant pretty printer is supposed to > show the active data field? I think that's already shown in your "with std" output above. It just happens that internalvar_void has no data fields. E.g., with: $ cat ./variant.cc #include #include int main () { std::variant v; v = "hello"; v = 1; return 0; } Stepping through the assignment lines, I get: (gdb) p v $1 = std::variant, std::allocator >, int> [index 0] = {"hello"} (gdb) n (gdb) p v $2 = std::variant, std::allocator >, int> [index 1] = {1} I wouldn't say this is super ideal output, as it forces you to count the types to know what index 0 and 1 are, though, as well as puts the data far off to the right.