From owner-freebsd-current Fri Jan 22 09:51:54 1999 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id JAA14378 for freebsd-current-outgoing; Fri, 22 Jan 1999 09:51:54 -0800 (PST) (envelope-from owner-freebsd-current@FreeBSD.ORG) Received: from cantor.boolean.net (cantor.boolean.net [209.133.111.73]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id JAA14373 for ; Fri, 22 Jan 1999 09:51:53 -0800 (PST) (envelope-from Kurt@OpenLDAP.Org) Received: from OpenLDAP.Org (localhost [127.0.0.1]) by cantor.boolean.net (8.9.1/8.9.1) with ESMTP id RAA21169; Fri, 22 Jan 1999 17:58:06 GMT (envelope-from Kurt@OpenLDAP.Org) Message-ID: <36A8BA23.8AE3B430@OpenLDAP.Org> Date: Fri, 22 Jan 1999 09:49:23 -0800 From: "Kurt D. Zeilenga" Organization: OpenLDAP X-Mailer: Mozilla 4.5 [en] (WinNT; I) X-Accept-Language: en-GB,en-US,en,de-DE,de MIME-Version: 1.0 To: "Richard Seaman, Jr." CC: freebsd-current@FreeBSD.ORG Subject: Re: -D_REENTRANT (Was: Using LinuxThreads) References: <19990119091151.F600@tar.com> <19990118182717.A15566@top.worldcontrol.com> <19990119024539.A88383@top.worldcontrol.com> <19990119140613.B826@shale.csir.co.za> <19990119091151.F600@tar.com> <19990121181228.A98581@shale.csir.co.za> <3.0.5.32.19990121114214.00958c30@localhost> <19990121143940.D5495@tar.com> <36A7A395.29B3E8A7@OpenLDAP.Org> <19990122114153.H92540@tar.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-current@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG "Richard Seaman, Jr." wrote: > > On Thu, Jan 21, 1999 at 02:00:53PM -0800, Kurt D. Zeilenga wrote: > > > > For kernel threading you just use libc. Whether or not libc generates > > > thread safe (re-entrant) calls depends on whether its also linked with > > > a library that 1) sets __isthreaded to a non-zero value, 2) has a _spinlock() > > > implementationm, and 3) implements the functions flockfile, funlockfile, etc. > > > There are also a few macros in header files that require _THREAD_SAFE to > > > be defined to be thread safe. > > > > > > I was hoping to be able to produce one ldap library that could be safely > > linked with or without threads. However, if I must define _THREAD_SAFE > > to generate code to be linked with threads then I must produce two libraries > > (-lfoolib compiled with -U_THREAD_SAFE and -lfoolib_r with -D_THREAD_SAFE). > > _THREAD_SAFE is only used in stdio.h. Looking at what's there, it could > be rewritten to eliminate _THREAD_SAFE entirely, at a (very slight) > performance penalty. You'd have to check __isthreaded (could be done > once, instead of twice, as in the code now) each time you call one > of the functions defined within the _THREAD_SAFE switch. All > _THREAD_SAFE does is let you avoid checking __isthreaded when you're > not threaded. So, if I want to produce a library which can be safely used by both threaded and non-threaded applications I should NOT define -D_THREAD_SAFE such that __isthreaded is always checked by the library. In effect, -D_THREAD_SAFE makes the generated code non-thread UNSAFE. - Kurt To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message