From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from zimbra.cs.ucla.edu (zimbra.cs.ucla.edu [131.179.128.68]) by sourceware.org (Postfix) with ESMTPS id D55AA3894C0F for ; Thu, 27 Aug 2020 18:21:59 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org D55AA3894C0F Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=cs.ucla.edu Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=eggert@cs.ucla.edu Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id BE5DB16008D; Thu, 27 Aug 2020 11:21:58 -0700 (PDT) Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id vSShnb9wlN88; Thu, 27 Aug 2020 11:21:57 -0700 (PDT) Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id D0081160101; Thu, 27 Aug 2020 11:21:57 -0700 (PDT) X-Virus-Scanned: amavisd-new at zimbra.cs.ucla.edu Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id P4fvGHJrWBDk; Thu, 27 Aug 2020 11:21:57 -0700 (PDT) Received: from [192.168.1.9] (cpe-75-82-69-226.socal.res.rr.com [75.82.69.226]) by zimbra.cs.ucla.edu (Postfix) with ESMTPSA id A317716008D; Thu, 27 Aug 2020 11:21:57 -0700 (PDT) Subject: Re: [PATCH v2] Ensure standard file descriptors are open on start To: Zack Weinberg Cc: =?UTF-8?Q?Arsen_Arsenovi=c4=87?= , GNU C Library References: <20200819124124.17481-1-arsen@aarsen.me> <20200819194025.5sgyd5avhduime4q@bstg> <20200819234519.l4enjvx4fsw42ltl@bstg> From: Paul Eggert Autocrypt: addr=eggert@cs.ucla.edu; prefer-encrypt=mutual; keydata= LS0tLS1CRUdJTiBQR1AgUFVCTElDIEtFWSBCTE9DSy0tLS0tCgptUUlOQkV5QWNtUUJFQURB QXlIMnhvVHU3cHBHNUQzYThGTVpFb243NGRDdmM0K3ExWEEySjJ0QnkycHdhVHFmCmhweHhk R0E5Smo1MFVKM1BENGJTVUVnTjh0TFowc2FuNDdsNVhUQUZMaTI0NTZjaVNsNW04c0thSGxH ZHQ5WG0KQUF0bVhxZVpWSVlYL1VGUzk2ZkR6ZjR4aEVtbS95N0xiWUVQUWRVZHh1NDd4QTVL aFRZcDVibHRGM1dZRHoxWQpnZDdneDA3QXV3cDdpdzdlTnZub0RUQWxLQWw4S1lEWnpiRE5D UUdFYnBZM2VmWkl2UGRlSStGV1FONFcra2doCnkrUDZhdTZQcklJaFlyYWV1YTdYRGRiMkxT MWVuM1NzbUUzUWpxZlJxSS9BMnVlOEpNd3N2WGUvV0szOEV6czYKeDc0aVRhcUkzQUZINmls QWhEcXBNbmQvbXNTRVNORnQ3NkRpTzFaS1FNcjlhbVZQa25qZlBtSklTcWRoZ0IxRApsRWR3 MzRzUk9mNlY4bVp3MHhmcVQ2UEtFNDZMY0ZlZnpzMGtiZzRHT1JmOHZqRzJTZjF0azVlVThN Qml5Ti9iClowM2JLTmpOWU1wT0REUVF3dVA4NGtZTGtYMndCeHhNQWhCeHdiRFZadWR6eERa SjFDMlZYdWpDT0pWeHEya2wKakJNOUVUWXVVR3FkNzVBVzJMWHJMdzYrTXVJc0hGQVlBZ1Jy NytLY3dEZ0JBZndoUEJZWDM0blNTaUhsbUxDKwpLYUhMZUNMRjVaSTJ2S20zSEVlQ1R0bE9n N3haRU9OZ3d6TCtmZEtvK0Q2U29DOFJSeEpLczhhM3NWZkk0dDZDCm5yUXp2SmJCbjZneGRn Q3U1aTI5SjFRQ1lyQ1l2cWwyVXlGUEFLK2RvOTkvMWpPWFQ0bTI4MzZqMXdBUkFRQUIKdENC UVlYVnNJRVZuWjJWeWRDQThaV2RuWlhKMFFHTnpMblZqYkdFdVpXUjFQb2tDUGdRVEFRSUFL QVVDVElCeQpaQUliQXdVSkVzd0RBQVlMQ1FnSEF3SUdGUWdDQ1FvTEJCWUNBd0VDSGdFQ0Y0 QUFDZ2tRN1pmcERtS3FmalJSCkd3LytJajAzZGhZZllsL2dYVlJpdXpWMWdHcmJIayt0bmZy SS9DN2ZBZW9GelE1dFZnVmluU2hhUGtabzBIVFAKZjE4eDZJREVkQWlPOE1xbzF5cDBDdEht ekdNQ0o1MG80R3JnZmpscjZnLyt2dEVPS2JobGVzek4yWHBKdnB3TQoyUWdHdm4vbGFUTFV1 OFBIOWFSV1RzN3FKSlpLS0tBYjRzeFljOTJGZWhQdTZGT0QwZERpeWhsREFxNGxPVjJtCmRC cHpRYmlvam9aelFMTVF3anBnQ1RLMjU3MmVLOUVPRVF5U1VUaFhyU0l6NkFTZW5wNE5ZVEZI czl0dUpRdlgKazlnWkRkUFNsM2JwKzQ3ZEd4bHhFV0xwQklNN3pJT053NGtzNGF6Z1Q4bnZE WnhBNUlaSHR2cUJsSkxCT2JZWQowTGU2MVdwMHkzVGxCRGgycWRLOGVZTDQyNlc0c2NFTVN1 aWc1Z2I4T0F0UWlCVzZrMnNHVXh4ZWl2OG92V3U4CllBWmdLSmZ1b1dJK3VSbk1FZGRydVk4 SnNvTTU0S2FLdlppa2tLczJiZzFuZHRMVnpIcEo2cUZaQzdRVmplSFUKaDYvQm1ndmRqV1Ba WUZUdE4rS0E5Q1dYM0dRS0tnTjN1dTk4OHl6bkQ3TG5COThUNEVVSDFIQS9HbmZCcU1WMQpn cHpUdlBjNHFWUWluQ21Ja0VGcDgzemwrRzVmQ2pKSjNXN2l2ekNuWW80S2hLTHBGVW05N29r VEtSMkxXM3haCnpFVzRjTFNXTzM4N01USzNDekRPeDVxZTZzNGE5MVp1Wk0vai9UUWRUTERh cU5uODNrQTRIcTQ4VUhYWXhjSWgKK05kOGsvM3c2bEZ1b0swd3JPRml5d2pMeCswdXI1am1t YmVjQkdIYzF4ZGhBRkc1QWcwRVRJQnlaQUVRQUthRgo2NzhUOXd5SDR3alRyVjFQejNjREVv U25WLzBaVXJPVDM3cDFkY0d5ai9JWHExeDY3MEhSVmFoQW1rMHNacFljCjI1UEY5RDVHUFlI RldsTmp1UFU5NnJEbmRYQjNoZWRtQlJoTGRDNGJBWGpJNERWK2JtZFZlK3EvSU1ubFpSYVYK bG05RWlNQ1ZBUjZ3MTNzUmV1N3FYa1c5cjNSd1kyQXpYc2twL3RBZTRCUktyMVptYnZpMm5i blE2ZXBFQzQycgpSYngwQjFFaGpiSVFaNUpIR2syNGlQVDdMZEJnbk5tb3M1d1lqendObGtN UUQ1VDBZZHpoazdKK1V4d0E1bTQ2Cm1PaFJEQzJyRlYvQTBnbTVUTHk4RFhqdi9Fc2M0Z1lu WWFpNlNRcW5VRVZoNUx1VjhZQ0pCbmlqcytUaXc3MXgKMWljbW42eEdJNDVFdWdKT2dlYyty THlwWWdwVnA0eDBISTVUODhxQlJZQ2t4SDNLZzhRbytFV05BOUE0TFJROQpEWDhuam9uYTBn ZjBzMDN0b2NLOGtCTjY2VW9xcVB0SEJuYzRlTWdCeW1DZmxLMTJlS2ZkMllZeG55ZzljWmF6 CldBNVZzbHZUeHBtNzZoYmc1b2lBRUgvVmcvOE14SHlBblBoZnJnd3lQcm1KRWNWQmFmZHNw Sm5ZUXhCWU5jbzIKTEZQSWhsT3ZXaDhyNGF0K3MrTTNMYjI2b1VUY3psZ2RXMVNmM1NEQTc3 Qk1SbkYwRlF5RSs3QXpWNzlNQk40eQpraXFhZXpReHRhRjFGeS90dmtoZmZTbzh1K2R3RzBF Z0poK3RlMzhnVGNJU1ZyMEdJUHBsTHo2WWhqcmJIclBSCkYxQ041VXVMOURCR2p4dU4zNVJM TlZFZnRhNlJVRmxSNk5jdFRqdnJBQkVCQUFHSkFpVUVHQUVDQUE4RkFreUEKY21RQ0d3d0ZD UkxNQXdBQUNna1E3WmZwRG1LcWZqU3JIQS8rS3pBS3ZUeFJoQTlNV05MeEl5SjdTNXVKMTZn cwpUM29DalpyQktHRWhLTU9HWDRPMEdBNlZPRXJ5TzdRUkNDWWFoM294U0czOElBbk5laXdK WGdVOUJ6a2s4NVVHCmJQRWQ3SEdGL1ZTZUhDUXdXb3U2anFVRFRTRHZuOVloTlRkRzBLWFBN NzRhQyt4cjJab3cxTzJtaFhpaGdXS0QKMER3KzBMWVBuVU9zUTBLT0Z4SFhYWUhtUnJTMU9a UFU1OUJMdmMrVFJoSWhhZlNIS0x3YlhLKzZja2t4Qng2aAo4ejVjY3BHMFFzNGJGaGRGWW5G ckVpZURMb0dtbkUyWUxoZFY2c3dKOVZOQ1M2cExpRW9oVDNmbTdhWG0xNXRaCk9JeXpNWmhI UlNBUGJsWHhRMFpTV2pxOG9ScmNZTkZ4YzRXMVVScEFrQkNPWUpvWHZRZkQ1TDNscUFsOFRD cUQKVXpZeGhIL3RKaGJEZEhycUhINzY3amFEYVRCMStUYWxwLzJBTUt3Y1hOT2Rpa2xHeGJt SFZHNllHbDZnOExyYgpzdTlOWkVJNHlMbEh6dWlrdGhKV2d6KzN2WmhWR3lObHQrSE5Jb0Y2 Q2pETDJvbXU1Y0VxNFJESE00NFFxUGs2Cmw3TzBwVXZOMW1UNEIrUzFiMDhSS3BxbS9mZjAx NUUzN0hOVi9waUl2Smx4R0FZejhQU2Z1R0NCMXRoTVlxbG0KZ2RoZDkvQmFiR0ZiR0dZSEE2 VTQvVDV6cVUrZjZ4SHkxU3NBUVoxTVNLbEx3ZWtCSVQrNC9jTFJHcUNIam5WMApxNUgvVDZh N3Q1bVBrYnpTck9MU280cHVqK0lUb05qWXlZSURCV3pobEExOWF2T2ErcnZVam1IdEQzc0ZO N2NYCld0a0dvaThidU5jYnk0VT0KPUFMNm8KLS0tLS1FTkQgUEdQIFBVQkxJQyBLRVkgQkxP Q0stLS0tLQo= Organization: UCLA Computer Science Department Message-ID: Date: Thu, 27 Aug 2020 11:21:57 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00, KAM_DMARC_STATUS, NICE_REPLY_A, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) 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: Thu, 27 Aug 2020 18:22:01 -0000 On 8/27/20 8:56 AM, Zack Weinberg wrote: > > https://lists.gnu.org/archive/html/autoconf-patches/2020-08/msg00025.html > ... but right now I am inclined *not* to put those > changes into the upcoming Autoconf 2.70. I responded in that there's a simple (3-line - see below) and portable-enough solution to the problem in Autoconf, since all we need to do is ensure that FDs 0 through 2 are open, not that they're open the right way. > After the experience of writing those patches, I'm definitely in favor > of GNU libc making a guarantee that fds 0,1,2 are open when > application code starts executing, for all processes, regardless of > what POSIX does or does not say. I agree they should be open. But it's better for FD 0 to be write-only and FDs 1+2 to be read-only, as that's more likely to prevent buggy programs from misbehaving further. For Autoconf, I suggest: (exec 3<&0) 2>/dev/null || exec 0>/dev/null (exec 3>&1) 2>/dev/null || exec 1&2) || exec 2