From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from omta002.cacentral1.a.cloudfilter.net (omta002.cacentral1.a.cloudfilter.net [3.97.99.33]) by sourceware.org (Postfix) with ESMTPS id 78DD83858D20 for ; Mon, 28 Feb 2022 18:55:58 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 78DD83858D20 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=SystematicSw.ab.ca Authentication-Results: sourceware.org; spf=none smtp.mailfrom=systematicsw.ab.ca Received: from shw-obgw-4002a.ext.cloudfilter.net ([10.228.9.250]) by cmsmtp with ESMTP id OUsundhmCgTZYOlBen5EX8; Mon, 28 Feb 2022 18:55:58 +0000 Received: from [10.0.0.5] ([184.64.124.72]) by cmsmtp with ESMTP id OlBdn61NDqyysOlBdnRu8l; Mon, 28 Feb 2022 18:55:58 +0000 X-Authority-Analysis: v=2.4 cv=Y6brDzSN c=1 sm=1 tr=0 ts=621d1abe a=oHm12aVswOWz6TMtn9zYKg==:117 a=oHm12aVswOWz6TMtn9zYKg==:17 a=IkcTkHD0fZMA:10 a=F4c1wLvTAfKac9Me7NQA:9 a=QEXdDO2ut3YA:10 Message-ID: Date: Mon, 28 Feb 2022 11:55:57 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.6.1 Reply-To: newlib@sourceware.org Subject: Re: [PATCH 2/2] newlib/libc/time/tzset_r.c(_tzset_unlocked_r): POSIX angle bracket <> support Content-Language: en-CA To: newlib@sourceware.org References: <20220225163959.48753-1-Brian.Inglis@SystematicSW.ab.ca> <20220225163959.48753-3-Brian.Inglis@SystematicSW.ab.ca> From: Brian Inglis Organization: Systematic Software In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CMAE-Envelope: MS4xfGn9hwm/j1eXALvF950UZuNR8TkjyU/e6VV75xWhmbKstRYvYcuPO+D4wOPYFEaF5EfQMN/3gzGn5iRGcfvECjwhl7q7963umVSS3/wGNl/Y7K8Rqj8h OmrjNnGlv6VJ+iX8cO5WYYZaPUST+PeyxaALxuuZLjZje2TBUGoGvtVFPLkPeCU5g/cOQSOs4hK8buOja0plq2726B5bCQmsB1s= X-Spam-Status: No, score=-1169.8 required=5.0 tests=BAYES_00, GIT_PATCH_0, KAM_DMARC_STATUS, KAM_LAZY_DOMAIN_SECURITY, NICE_REPLY_A, RCVD_IN_MSPIKE_H5, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE 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: newlib@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Newlib mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 28 Feb 2022 18:55:59 -0000 On 2022-02-28 05:04, Corinna Vinschen wrote: > Hi Brian, > > On Feb 25 09:39, Brian Inglis wrote: >> >> define POSIX specified minimum TZ abbr size 3 TZNAME_MIN >> use limits.h TZNAME_MAX, _POSIX_TZNAME_MAX, unistd.h sysconf(_SC_TZNAME_MAX) >> issue error if no symbols defined (document fallback value in case required) >> allow POSIX angle bracket < > quoted signed alphanumeric tz abbr e.g. >> allow POSIX unquoted alphabetic tz abbr e.g. MESZ >> apply same changes for DST tz abbr >> --- >> newlib/libc/time/tzset_r.c | 74 ++++++++++++++++++++++++++++++++------ >> 1 file changed, 64 insertions(+), 10 deletions(-) >> > >> diff --git a/newlib/libc/time/tzset_r.c b/newlib/libc/time/tzset_r.c >> index 9e0cf834bd6b..6a5fd578c0be 100644 >> --- a/newlib/libc/time/tzset_r.c >> +++ b/newlib/libc/time/tzset_r.c >> @@ -1,14 +1,30 @@ >> #include <_ansi.h> >> +#include /* {,_POSIX_}TZNAME_MAX */ >> #include >> #include >> #include >> #include >> +#include /* sysconf(_SC_TZNAME_MAX) */ >> #include >> #include >> #include "local.h" >> >> #define sscanf siscanf /* avoid to pull in FP functions. */ >> >> +#define TZNAME_MIN 3 /* POSIX specified minimum TZ abbr size */ > > Are you sure? Minimum is historical. >> +/* TZNAME_MAX - POSIX specified maximum TZ abbr size */ >> +/* define TZNAME_MAX if undefined and available */ >> +#if !defined(TZNAME_MAX) >> +#if defined(_POSIX_TZNAME_MAX) >> +#define TZNAME_MAX _POSIX_TZNAME_MAX /* use POSIX value */ >> +#elif defined(_SC_TZNAME_MAX) >> +#define TZNAME_MAX sysconf(_SC_TZNAME_MAX) /* use sysconf value */ > > This is not a safe bet. _SC_TZNAME_MAX is defined in unistd.h > unconditionally, even for targets not providing sysconf(). And Why define indices if they are unusable on that platform? > given that _POSIX_TZNAME_MAX is only defined for RTEMS and Cygwin, > this will run into problems on most other targets. > > Only Phoenix-RTOS, RISCV, RTEMS and Cygwin support sysconf, and none > of them actually supports _SC_TZNAME_MAX as parameter. And even Cygwin > returns -1 and sets errno to EINVAL. > > Given you're checking _POSIX_TZNAME_MAX first, which is defined on > Cygwin, the sysconf path will never be used there anyway. But that's > actually a minor point. > > The real problem is, you can't use sysconf(_SC_TZNAME_MAX) like this: > - You don't know at compile time if the function is really supported. > - You don't know if _SC_TZNAME_MAX returns a positive value or -1. The docs appeared unclear whether the index or return value could be -1. POSIX sysconf(3p) man page says -1/EINVAL means invalid argument value which should not apply if _SC_TZNAME_MAX is defined, otherwise -1/errno is unchanged means no definite limit?! I can just enclose it in HAVE_SYSCONF, else define a macro returning -1, and leave it at that for our purposes, while allowing for any platform that decides to support it. > And then again, there's no good reason to check against _POSIX_TZNAME_MAX > either. _POSIX_TZNAME_MAX is a system-independent definition, defining > a *minimum* value which has to be supported by the OS. So any OS can > define TZNAME_MAX as _POSIX_TZNAME_MAX, or any bigger value, or not at > all, if there just is no limit. > > So, either the system defines TZNAME_MAX, or the system provides > sysconf() *and* sysconf(_SC_TZNAME_MAX) returns a positive value. In > these cases, a check against that value makes sense. In all other > cases, there's just no limit to check for. So I may as well default to using the hardwired limit of 10, which is the most sensible value allowing for five letters, sign, four digits. -- Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada This email may be disturbing to some readers as it contains too much technical detail. Reader discretion is advised. [Data in binary units and prefixes, physical quantities in SI.]