Date: Mon, 29 Oct 2001 04:05:37 -0800 (PST) From: Lamont Granquist <lamont@scriptkiddie.org> To: <freebsd-hackers@freebsd.org> Subject: Re: MT-Safe wrapper around memcpy()? Message-ID: <20011029040255.D27876-100000@coredump.scriptkiddie.org> In-Reply-To: <20011029005821.X15052@elvis.mu.org>
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On Mon, 29 Oct 2001, Alfred Perlstein wrote: > * Alfred Perlstein <bright@mu.org> [011029 00:53] wrote: > > * Lamont Granquist <lamont@scriptkiddie.org> [011029 00:43] wrote: > > > > > > I'm trying to figure out the best way to write a wrapper around memcpy() > > > which can call fprintf() without winding up getting into a recursive > > > loop. The problem is that fprintf() will call memcpy() and around and > > > around we go. > > > > > > I can use a global variable to prevent this, but that usage isn't thread > > > safe. I can make it thread safe by using pthread keys, but then i have to > > > link in libc_r, and for non-pthreaded programs i don't want to do that. > > > > > > Anyone have any suggestions? Right now I'm almost thinking that I just > > > need to directly patch libc and libc_r. It might be an ugly patch though, > > > and I'd rather not have this patch mandate recompiling all of libc. > > > > Where do you see mem* calling printf? > > Uh, nevermind. :) > > Ok, what you want to do is use a nested flag in memcpy so you > don't recurse, there's some code in libc that's conditionally > compiled when compiling libc_r, _THREAD_SAFE or something is > defined, once you find that then just simply use the global > for non threaded programs and keys for threaded ones. you mean like localtime.c: #ifdef _THREAD_SAFE pthread_mutex_lock(&lcl_mutex); #endif and such? problem is that i could do that if i was dropping it into libc itself, but as a single .so that i want to LD_PRELOAD, i need a run-time conditional rather than a precompiler conditional. i think i may be asking for a lot... To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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