From nobody Wed Oct 9 19:29:23 2024 X-Original-To: dev-commits-src-all@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4XP3cC0JwQz5YwMP; Wed, 09 Oct 2024 19:58:51 +0000 (UTC) (envelope-from steffen@sdaoden.eu) Received: from sdaoden.eu (sdaoden.eu [217.144.132.164]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4XP3cB4qsxz4Sy4; Wed, 9 Oct 2024 19:58:50 +0000 (UTC) (envelope-from steffen@sdaoden.eu) Authentication-Results: mx1.freebsd.org; none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sdaoden.eu; s=citron; t=1728503921; x=1729170587; h=date:author:from:to:cc:subject: message-id:in-reply-to:references:mail-followup-to:openpgp:blahblahblah: mime-version:content-type:content-transfer-encoding:author:from:subject: date:to:cc:resent-author:resent-date:resent-from:resent-sender:resent-to: resent-cc:resent-reply-to:resent-message-id:in-reply-to:references: mime-version:content-type:content-transfer-encoding:content-disposition: content-id:content-description:message-id:mail-followup-to:openpgp: blahblahblah; bh=7tWWpKKkeRydccHjBhxMKNGzA3meQ3M4davhQlW2GLQ=; b=Q+sqhYUEU+Su50y6VNtxbdPwxYHm2KwIZkiVnF/2QA+hr6FXk5vJEWLWkyidyivk6hGbcilH C9lHwzxGds6gNE0+ADfZhJ7/JksvMPcBMZ+tjhJARiPx82+tWT5dUoGvabJdKwztf4coB1AloP +FlNee5E4lro2rQUy1wOswRW0xGsfZySNNkupzHiBe/jp/6jeOD0HBnRp7uPSXRwnLSThEa2Sy BW+on2ZSXBOSHcaFPUY/kONJ/TnX5M3OhKrjj83MAnSy0Gd986ID9THOJN5n/dWh0rEFkQUanm lKRTXVZLV85tFSAgauiEVAyJk4/y9+HQKBU1mLEbW+wJCMqw== DKIM-Signature: v=1; a=adaed25519-sha256; c=relaxed/relaxed; d=sdaoden.eu; s=orange; t=1728503921; x=1729170587; h=date:author:from:to:cc:subject: message-id:in-reply-to:references:mail-followup-to:openpgp:blahblahblah: mime-version:content-type:content-transfer-encoding:author:from:subject: date:to:cc:resent-author:resent-date:resent-from:resent-sender:resent-to: resent-cc:resent-reply-to:resent-message-id:in-reply-to:references: mime-version:content-type:content-transfer-encoding:content-disposition: content-id:content-description:message-id:mail-followup-to:openpgp: blahblahblah; bh=7tWWpKKkeRydccHjBhxMKNGzA3meQ3M4davhQlW2GLQ=; b=hKahXJQcU3yhekazOFphSbXiQosjHcbxraLXEYcOi/rkdZdz+wvtiAV7mM24/+NfyDdEdn8B TvpPjrRRJ2nIAQ== Date: Wed, 09 Oct 2024 21:29:23 +0200 Author: Steffen Nurpmeso <steffen@sdaoden.eu> From: Steffen Nurpmeso <steffen@sdaoden.eu> To: Kyle Evans <kevans@FreeBSD.org> Cc: Konstantin Belousov <kostikbel@gmail.com>, src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org, Dag-Erling =?utf-8?Q?Sm=C3=B8rgrav?= <des@freebsd.org> Subject: Re: git: c2d93a803ace - main - env: Check the status of stdout. Message-ID: <20241009192923.hYP_AEIt@steffen%sdaoden.eu> In-Reply-To: <91c60145-9f13-48a6-b7cd-4a1a9703e67c@FreeBSD.org> References: <202410081702.498H2KIP072012@gitrepo.freebsd.org> <ZwVuwK9Lry_6JDay@kib.kiev.ua> <86iku2v3o2.fsf@ltc.des.dev> <ZwZ0erARk2ZKAeBv@kib.kiev.ua> <91c60145-9f13-48a6-b7cd-4a1a9703e67c@FreeBSD.org> Mail-Followup-To: Kyle Evans <kevans@FreeBSD.org>, Konstantin Belousov <kostikbel@gmail.com>, src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org, Dag-Erling =?utf-8?Q?Sm=C3=B8rgrav?= <des@freebsd.org> User-Agent: s-nail v14.9.25-608-ge479530e8d OpenPGP: id=EE19E1C1F2F7054F8D3954D8308964B51883A0DD; url=https://ftp.sdaoden.eu/steffen.asc; preference=signencrypt BlahBlahBlah: Any stupid boy can crush a beetle. But all the professors in the world can make no bugs. List-Id: Commit messages for all branches of the src repository <dev-commits-src-all.freebsd.org> List-Archive: https://lists.freebsd.org/archives/dev-commits-src-all List-Help: <mailto:dev-commits-src-all+help@freebsd.org> List-Post: <mailto:dev-commits-src-all@freebsd.org> List-Subscribe: <mailto:dev-commits-src-all+subscribe@freebsd.org> List-Unsubscribe: <mailto:dev-commits-src-all+unsubscribe@freebsd.org> X-BeenThere: dev-commits-src-all@freebsd.org Sender: owner-dev-commits-src-all@FreeBSD.org MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[]; ASN(0.00)[asn:15987, ipnet:217.144.128.0/20, country:DE] X-Rspamd-Queue-Id: 4XP3cB4qsxz4Sy4 X-Spamd-Bar: ---- Kyle Evans wrote in <91c60145-9f13-48a6-b7cd-4a1a9703e67c@FreeBSD.org>: |On 10/9/24 07:18, Konstantin Belousov wrote: |> On Tue, Oct 08, 2024 at 08:40:45PM +0200, Dag-Erling Sm=C3=B8rgrav wrot= e: |>> Konstantin Belousov <kostikbel@gmail.com> writes: |>>> Dag-Erling Sm=C3=B8rgrav <des@FreeBSD.org> writes: |>>>> + if (fflush(stdout) !=3D 0) |>>>> + err(1, "stdout"); |>>> Why is this check needed? |>> |>> POSIX requires it. |> Could you please point me to the requirement? |>=20 | |Seconding the assertion that it's somewhere in there, but it's also just= =20 |a reasonable thing to do. The implicit flush at exit of streams in libc= =20 |has to ignore errors because it lacks the necessary context to be able=20 |to surface anything, so applications must do it on an individual basis=20 |to appropriately surface, e.g., output truncation issues that are=20 |otherwise hidden (and maybe not obvious) from the caller. | |The impression I had from talking to folks about this in the past is=20 |that it's practically expected that applications will flush-and-error at= =20 |the end rather than check individual writes so that they can surface=20 |logic/execution errors at a higher priority than stdout errors, but=20 |stdout errors should still prevent a clean exit. The POSIX core developer Geoff Clare said on 2021-07-01, message 20210701104540.GA4023@localhost: ... |The standard says nothing about internal buffering; it just requires |pwd to write the directory to file descriptor 1. It also states that |exit status 0 means "successful completion". Together, these |requirements mean that a conforming pwd must not exit with status 0 |if it did not write the directory to fd 1. | |If an implementor chooses to buffer the output, then it is their |responsibility to check that the buffer is successfully flushed to |fd 1 before exiting with status 0. ... |As above, this is all irrelevant to what the standard requires. | |As far as implementation detail goes, obviously if pwd uses stdio |buffering then in order to conform to the standard it must explicitly |fflush(stdout) and check there was no write error before exiting. |I see from later in the thread that mksh has now been patched to do |exactly that. (Thanks Thorsten.) --steffen | |Der Kragenbaer, The moon bear, |der holt sich munter he cheerfully and one by one |einen nach dem anderen runter wa.ks himself off |(By Robert Gernhardt)