Date: Fri, 22 Jan 1999 10:44:03 -0800 From: "Kurt D. Zeilenga" <Kurt@OpenLDAP.Org> To: "Richard Seaman, Jr." <dick@tar.com> Cc: freebsd-current@FreeBSD.ORG Subject: Re: -D_REENTRANT (Was: Using LinuxThreads) Message-ID: <36A8C6F3.5D611CA9@OpenLDAP.Org> References: <Pine.BSF.4.05.9901182203500.11971-100000@janus.syracuse.net> <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> <36A8BA23.8AE3B430@OpenLDAP.Org> <19990122121949.I92540@tar.com>
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"Richard Seaman, Jr." wrote: > > On Fri, Jan 22, 1999 at 09:49:23AM -0800, Kurt D. Zeilenga wrote: > > "Richard Seaman, Jr." wrote: > > > _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. > > I guess I was a little unclear. > > 1) I think you would have to rewrite a little bit of the header to > use the __isthreaded test on a couple of more functions. > > 2) If you always define -D_THREAD_SAFE, __isthreaded will be > checked whether you're threaded or not. I would think that most third party libraries (from Ports) do not compile with -D_THREAD_SAFE. As such, __isthreaded won't be checked and the library cannot be safely used in a threaded environment. > You could also just eliminate _THREAD_SAFE entirely by letting > __isthreaded get checked on each relevant call. I would much prefer this. Then third party libraries compiled without -D_THREAD_SAFE can be used in threaded environments (though they might require external synchronization). Kurt To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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