From owner-freebsd-hackers@FreeBSD.ORG Fri Jan 16 10:36:01 2009 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 6EC38106564A for ; Fri, 16 Jan 2009 10:36:01 +0000 (UTC) (envelope-from yanefbsd@gmail.com) Received: from mail-bw0-f20.google.com (mail-bw0-f20.google.com [209.85.218.20]) by mx1.freebsd.org (Postfix) with ESMTP id BEB0C8FC1E for ; Fri, 16 Jan 2009 10:36:00 +0000 (UTC) (envelope-from yanefbsd@gmail.com) Received: by bwz13 with SMTP id 13so5301674bwz.19 for ; Fri, 16 Jan 2009 02:35:59 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:cc:content-type :content-transfer-encoding; bh=IR5F44MNa2CyamvnthfrY26YDZFsRYMnrBm3ctWw4lM=; b=ClrgP5GsdMCWHzU5rZDi8mCZpufpE6cHI9s3wW5hfHsTIT5UXPGIQNQxdXVf/6idy1 wYbj9uw7kWj+VvWR8dB8LG3Vh5wGTG/52bJPJZrKA2TaerrZ7pGpDChZv4X0aB/jPP1A iLMaJA/6k5Q5kDxAUJ+QQA9GixVHPUy45AuoI= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=CZOqtm5WZdH504q2Wq6vwBPtZjukMGXTemwF8KWQMpuHSgIDVWn89ALZnOmL7KaJKX f3KErvGj1Ojm8qO7NkIdTOR/ZDXoxT1gCep+0sfKAQQGFVY9DmtlRI54cqILnD1CM8Lp K1U711GDTcOmgy88n+eg4o2ETItEaAbbnbfdc= MIME-Version: 1.0 Received: by 10.181.134.11 with SMTP id l11mr798578bkn.73.1232102159587; Fri, 16 Jan 2009 02:35:59 -0800 (PST) In-Reply-To: <49705FA2.2020605@gmx.de> References: <7d6fde3d0901160041n55466290l55f737d274a40895@mail.gmail.com> <49704AEC.3080709@gmx.de> <200901161039.00232.christian.kandeler@hob.de> <49705FA2.2020605@gmx.de> Date: Fri, 16 Jan 2009 02:35:59 -0800 Message-ID: <7d6fde3d0901160235o6aa1f096q11c5096b70f3577@mail.gmail.com> From: Garrett Cooper To: Christoph Mallon Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: Christian Kandeler , freebsd-hackers@freebsd.org Subject: Re: Confused by segfault with legitimate call to strerror(3) on amd64 / sysctl (3) setting `odd' errno's 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: Fri, 16 Jan 2009 10:36:01 -0000 On Fri, Jan 16, 2009 at 2:21 AM, Christoph Mallon wrote: > Christian Kandeler schrieb: >> >> On Friday 16 January 2009 09:53, Christoph Mallon wrote: >> >>>> int >>>> main() { >>>> >>>> int mib[4]; >>>> >>>> size_t len; >>>> >>>> if (sysctlnametomib("kern.ipc.shmmax", mib, &len) !=3D 0) { >>>> printf("Errno: %d\n", errno); >>>> errx(errno, "Error: %s", strerror(errno)); >>> >>> The use of errno is wrong. printf might change errno. >> >> I don't think printf() can set errno. And even if it could, it > > Of course it can. See ISO/IEC 9899:1999 (E) =A77.5:3. > >> wouldn't matter, because C has call-by-value semantics. > > This has nothing to do with call-by-value. errno is read (even twice!) > *after* the call to printf(). Ok, I just installworld'ed, recompiled the program with the following modifications, and I still get segfaults. And the question of the night is: why amd64 on a VERY recent CURRENT? I'm going to try the same app on an amd64 freebsd VMware instance with RELENG_7. Remember: just because a bunch of other people aren't reporting issues with CURRENT/amd64 doesn't mean that it isn't environmental, related to my hardware or compile options ;). Cheers, -Garrett #include #include #include int main() { struct stat sb; int o_errno; if (stat("/some/file/that/doesn't/exist", &sb) !=3D 0) { o_errno =3D errno; printf("Errno: %d\n", errno); printf("%s\n", strerror(o_errno)); } return 0; } #include #include #include int main() { struct stat sb; int o_errno; if (stat("/some/file/that/doesn't/exist", &sb) !=3D 0) { o_errno =3D errno; printf("Errno: %d\n", errno); printf("%s\n", strerror(o_errno)); } return 0; } [gcooper@optimus ~]$ gcc -o badfile badfile.c [gcooper@optimus ~]$ ./badfile Errno: 2 Segmentation fault: 11 (core dumped) [gcooper@optimus ~]$