X-Recipient: archive-cygwin AT delorie DOT com X-SWARE-Spam-Status: No, hits=-1.8 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_NONE,RCVD_IN_HOSTKARMA_YE X-Spam-Check-By: sourceware.org X-Mail-Handler: Dyn Standard SMTP by Dyn X-Report-Abuse-To: abuse AT dyndns DOT com (see http://www.dyndns.com/services/sendlabs/outbound_abuse.html for abuse reporting information) X-MHO-User: U2FsdGVkX1/QuR8IXjAXXIkLZuCs+xih Date: Tue, 4 Sep 2012 17:51:29 -0400 From: Christopher Faylor To: cygwin AT cygwin DOT com Subject: Re: limitations of TLS using GCC's __thread keyword and Cygwin Message-ID: <20120904215129.GA30731@ednor.casa.cgf.cx> Reply-To: cygwin AT cygwin DOT com Mail-Followup-To: cygwin AT cygwin DOT com References: <504612A3 DOT 6070605 AT cs DOT utoronto DOT ca> <50466981 DOT 70005 AT gmail DOT com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <50466981.70005@gmail.com> User-Agent: Mutt/1.5.20 (2009-06-14) Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner AT cygwin DOT com Mail-Followup-To: cygwin AT cygwin DOT com Delivered-To: mailing list cygwin AT cygwin DOT com On Tue, Sep 04, 2012 at 10:50:09PM +0200, V??clav Zeman wrote: >On 09/04/2012 04:39 PM, Ryan Johnson wrote: >> On 04/09/2012 8:58 AM, V??clav Zeman wrote: >>> Hi. >>> >>> I am am porting a library that can use the __thread keyword in its >>> internals to provide thread local storage. Now, with MSVC there is a >>> limitation on pre-Vista Windows (see [1]) that DLLs using >>> __declspec(thread) (MSVC equivalent of GCC's __thread) cannot be >>> loaded using LoadLibrary() because pre-Vista Windows allocate the TLS >>> declared that way only on process startup. Vista and later Windows do >>> not seem to have the limitation. Since Cygwin officially still >>> supports at least Windows XP, I want to provide a library that works >>> there as well. >>> >>> Does Cygwin's GCC and its TLS emulation work around this problem? IOW, >>> are Cygwin DLLs using TLS declared using __thread keyword safe to be >>> loaded using LoadLibrary()/dlopen() or are they not safe to be loaded >>> that way? >>> >>> [1] http://msdn.microsoft.com/en-us/library/2s9wt68x.aspx >>> >> I suspect it's not a problem, but if I were you I'd write a simple >> test program to see. Unfortunately, TLS in general seems broken on my >> machine when I tried it, but that might be due to my home-brew gcc >> being configured wrong or something. >I would have done that already but I do not have any Windows XP machine >to try this on. I don't believe that __thread is implemented on Cygwin. cgf -- 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