From owner-freebsd-hackers@FreeBSD.ORG Wed Apr 23 09:19:55 2008 Return-Path: Delivered-To: hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id BD3091065675 for ; Wed, 23 Apr 2008 09:19:55 +0000 (UTC) (envelope-from yanefbsd@gmail.com) Received: from fg-out-1718.google.com (fg-out-1718.google.com [72.14.220.153]) by mx1.freebsd.org (Postfix) with ESMTP id 17A448FC18 for ; Wed, 23 Apr 2008 09:19:54 +0000 (UTC) (envelope-from yanefbsd@gmail.com) Received: by fg-out-1718.google.com with SMTP id 16so2750721fgg.35 for ; Wed, 23 Apr 2008 02:19:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:to:subject:in-reply-to:mime-version:content-type:references; bh=UjRSVyOdO4vVW4OcIHDKhwZBd+VKdXxJHL+GkiIonYc=; b=PktifkfiBtYwZhxOXv8JofYMcPWvXgFDeaRpTQ4W0/e8iOFyP6hb5EI2PsLudRrjJHwGW/3WBVZlejnGmOhbm5v0A7sanxDpZjMVOut/aaao0kamu49xhZ0KK1t8CiYOq5TItG0vOyuvq0gzrT4GZGUm9I2nBNLkvWvgvKJyRzQ= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:in-reply-to:mime-version:content-type:references; b=AB5TfNUeecPTcb2vt9Wbxuoxn0nlWDR+PGe3sQVCMWGO0AjLgtz7UJs1JY1CM4I4oxT9Cedai7eEa1dMtzA9jvPdaJpqJJ0vqtKKwf+wIo4NDZPIvdCl5E2TC4jMTwpgVlnGwUvOytbs+sHjlMCzr55GdU2z6kZzEtCbUltC+/k= Received: by 10.86.82.16 with SMTP id f16mr2710040fgb.60.1208942393307; Wed, 23 Apr 2008 02:19:53 -0700 (PDT) Received: by 10.86.26.8 with HTTP; Wed, 23 Apr 2008 02:19:53 -0700 (PDT) Message-ID: <7d6fde3d0804230219q13d204f2wda4a5f271b9a0e66@mail.gmail.com> Date: Wed, 23 Apr 2008 02:19:53 -0700 From: "Garrett Cooper" To: hackers@freebsd.org In-Reply-To: <7d6fde3d0804230219x209bd707u30150581abc74802@mail.gmail.com> MIME-Version: 1.0 References: <7d6fde3d0804222240j6b42b77yd86d8accb5a959fa@mail.gmail.com> <20080423025048.6b51a580@bhuda.mired.org> <5F412E73-29FC-4876-A6F0-9BC269876192@bitpowder.com> <7d6fde3d0804230219x209bd707u30150581abc74802@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Cc: Subject: Fwd: strdup(NULL) supposed to create SIGSEGV? X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 23 Apr 2008 09:19:55 -0000 On Wed, Apr 23, 2008 at 1:30 AM, Bernard van Gastel wrote: > > Op 23 apr 2008, om 08:50 heeft Mike Meyer het volgende geschreven: > > > On Tue, 22 Apr 2008 22:40:21 -0700 > > "Garrett Cooper" wrote: > > > > Hi all, > > > I made an oops in a program, which uncovered "feature" in strdup(2) > > > that I wasn't aware of before. So I was wondering, is strdup(pointer = > > > NULL) > > > supposed to segfault should this just return NULL and set errno? > > > > > > > Yes, it's supposed to segfault. Check out what, say, strcpy does if > > you ask it to copy a NULL pointer. And this is an improvement from the > > bad old days, when they would happily walk through memory starting at > > 0..... > > > > I don't like it this way. I would like: > > strdup(NULL) = NULL > strdup(string) = copy of string > > strcpy(NULL, NULL) = NULL > strcpy(s1, NULL) = ERROR > strcpy(NULL, s2) = NULL (with s2 unchanged) > strcpy(s1, s2) = normal > > But I am not sure of the implications. Maybe in some situation it is > bad... Anyone? > > > > Besides, errno is used to signal errors from system calls. strdup > > isn't a system call, it's a library function (says so at the top of > > the man page). > > > > But strdup uses malloc, which is a system call (from the strdup manual: If > insufficient memory is available, NULL is returned and errno is set to > ENOMEM.) > > Regards, > Bernard > > I was more concerned about the fact that there wasn't any documentation that said something -- either implicitly or explicitly -- that strdup(NULL) causes a segfault. Of course I did some more research after you guys gave me some replies and realized I'm not the first person to bumble across this fact, but I haven't found FreeBSD or Linux documentation supporting that errata. It was harmless in my tiny program, but I would hate to be someone adding that assumption to a larger project with multiple threads and a fair number of lines... *shrugs*. -Garrett PS I'm as much against POLA changes as the next guy. I just don't like shooting myself in the foot too terribly much :).