From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr1-x42b.google.com (mail-wr1-x42b.google.com [IPv6:2a00:1450:4864:20::42b]) by sourceware.org (Postfix) with ESMTPS id 37F303858401 for ; Mon, 8 Nov 2021 13:36:56 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 37F303858401 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=jguk.org Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=jguk.org Received: by mail-wr1-x42b.google.com with SMTP id t30so26927263wra.10 for ; Mon, 08 Nov 2021 05:36:56 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=jguk.org; s=google; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=PCpYDr2rMf1Po2qbVt1l/VrbTEEWHf/DgAnYwV+2g0s=; b=qMwul0mClKtSn9Opty2oCnO1c+CIwAhLdYXNWiWGhfc0pc67T88SDUAiZ3r1Okfgqs 5R9a1aCwwLIF2kuUZlZoIpyprn/mfYZnmyR2LOb3seVkAuKwqHiozH8Hy/mo10ia1Emv Jq2YkoDexC/ZDs8ZpNLxYdW5+WrvacBB+G/MaK3RORTWxMWAjBtlIxh5+XGfFBJNf/YM KINOHXaFRILQay5J7153ahMuRRdOdebxmsFOTT5CAlmYvFqHxaP14iLXaVfjCWJk4rua gS8tSeVandKzDf2T7qBuS98sRuJgp74hwqvVPAcU6Zqv/AUheglnOU/myr8manphfx6p 69mQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=PCpYDr2rMf1Po2qbVt1l/VrbTEEWHf/DgAnYwV+2g0s=; b=o3KEvJTPIyRyIGbjtLVubpFEfes3e+5xODqELgwwC6m4Yn2MNPS9SnJWnZo8QdtDx1 r9+VSs4HHAM4TugFZVIEI+nXqsamHB5JZ8jV7Z3Z+KJaYCTcofmok+klXNOie1UGSyHy fPdrb3eiDdc6XflN8/3FrylnFEdVQSoby18iHZR6rlw5U1DQWMgIcQSbFcTaswwT2e/U sKJ7q8LjDxUOCKY+/D2tQvdpzRHJys+v/L3tvSSTChGENaMRgukfOi3WIUFSfn0+Wdvv bVNVXzyanRV7T+H/RjNQr3/ose8bLmP9HM4wYfFlAUXDbvOSKIio/UFbcH0V4f4XGESC BxOw== X-Gm-Message-State: AOAM530oGROobgtmBZhESWf9viazilmbR4I2hyAx93DUJhHdvpNPFGL8 j8xLI/FOPAjjRF0KSWA5n4Ha6FmhT3D6IA== X-Google-Smtp-Source: ABdhPJzaUuy8haGrVLWw4hYuwXIcDWJdTQRAi7Df7zEUqwEgBVPXqcbO5xzPjDvPSxX0aInE4+N5zQ== X-Received: by 2002:a5d:6691:: with SMTP id l17mr84267757wru.227.1636378615341; Mon, 08 Nov 2021 05:36:55 -0800 (PST) Received: from [192.168.0.12] (cpc87345-slou4-2-0-cust172.17-4.cable.virginm.net. [81.101.252.173]) by smtp.gmail.com with ESMTPSA id c11sm20132099wmq.27.2021.11.08.05.36.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 08 Nov 2021 05:36:54 -0800 (PST) Subject: Re: glibc strerrorname_np To: Florian Weimer Cc: GNU C Library References: <874k8nniw4.fsf@oldenburg.str.redhat.com> From: Jonny Grant Message-ID: Date: Mon, 8 Nov 2021 13:36:54 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <874k8nniw4.fsf@oldenburg.str.redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-5.0 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, NICE_REPLY_A, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 08 Nov 2021 13:36:58 -0000 On 08/11/2021 08:36, Florian Weimer wrote: > * Jonny Grant: > >> I noticed on the man page it may return NULL, which is a shame, as then it means we always need to check that before using in every printf etc :- >> >> printf("err %s\n", strerrorname_np(myerr)?strerrorname_np(myerr), "Unknown err"); > > We can add %#m to printf for this use case. It would print the errno > constant if known, or a number otherwise. To use it, errno needs to be > assigned before calling printf. Printing multiple error codes would not > be possible directly, but such usage is quite rare. Hi Florian I couldn't find a reference description of %#m - May I ask if you have a link? I see %m is a GNU printf extension. Still feels risky, relying on all calling code that currently uses strerror() to also change from %s to %#m to avoid a NULL ptr SEGV. With kind regards Jonny