DomainKey-Signature: a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:subject:to:references:reply-to:cc:from
	:message-id:date:mime-version:in-reply-to:content-type
	:content-transfer-encoding; q=dns; s=default; b=KgGYXvSprmOzK2TK
	PQSLfSQT3F+EvOfKdab/sSfpMFIah9FKv8C9BFmYYKQrYEOL1WXbJGZxFD/3fuX6
	nR1JFi3eH7PlSOdJVrG23nO4CepmlPN6kOlgNY75PH3OBwAmP3A5vqej/XxooGZT
	iJwx6Mt+3WprBgQ8rIRo6pza4sc=
Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm
Sender: cygwin-owner AT cygwin DOT com
Mail-Followup-To: cygwin AT cygwin DOT com
Subject: Re: Seg Fault in strftime
To: cygwin AT cygwin DOT com
References: <CAOC2fq9A1DSjy=7Af=wVCkNEsttpd4Fj-0w_nNwnSb76WFt5WA AT mail DOT gmail DOT com>
Reply-To: cygwin AT cygwin DOT com
Cc: mike AT kmcardiff DOT com
From: Jon TURNEY <jon DOT turney AT dronecode DOT org DOT uk>
Message-ID: <55BB6F59.8060905@dronecode.org.uk>
Date: Fri, 31 Jul 2015 13:51:37 +0100
User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0
MIME-Version: 1.0
In-Reply-To: <CAOC2fq9A1DSjy=7Af=wVCkNEsttpd4Fj-0w_nNwnSb76WFt5WA@mail.gmail.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit

On 31/07/2015 01:16, Michael Enright wrote:
> The tznam is set from the tmzone member and when this happens that
> member is garbage. This member is garbage POSSIBLY because of a
> configuration option in libmozjs. The calling code is in prmjtime.cpp
> fills in a struct tm from Spidermonkey's own broken-down time
> structure, 'a', and then if the configuration enables, it makes
> *another* struct tm with more fields filled in in order to get
> a.tm_zone's proper value. My guess is that the path is not enabled but
> the bits delivered to me do not disclose whether this righteous code
> path is enabled. __cygwin_gettzname is evidently compiled to expect
> the tm_zone member to exist because GDB shows it does exist.

Thanks for this investigation and analysis.

> So did any aspect of this change recently? The application and library
> were getting along okay before I did cygwin updates. The last time I
> had tried to run this code was early June, at which time I was running
> it dozens of times a day.

[1] looks like a highly relevant change and [2] is the associated discussion

It would be very helpful if you could tweak the testcase there and 
produce one which reproduces your problem.

[1] 
https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;a=commitdiff;h=75d5f68aabf62c42884ff935f888b12bbcd00001
[2] https://sourceware.org/ml/newlib/2015/msg00321.html

> Also it appears that the tm_zone member is an extension. I haven't
> been able to find POSIX guidance about how applications are supposed
> use struct tm in compliance in the presence of implementation-defined
> fields. POSIX example code shows a usage that does access the 'at
> least' fields. The language allows for implementation-defined fields.
> No mechanism is provided within POSIX to allow an application to
> discover additional fields and take care of them. It seems to me that
> an application can then assume that when it provides a struct tm as
> input, filling in the time and date reasonably, it is always
> sufficient to fill in the 'at least' fields and the implementation is
> the one who has to assume that the rest of the fields might not be
> filled in.

Yeah, this seems a bit of an under-specified area.


--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple