Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751299AbeAPRTR (ORCPT + 1 other); Tue, 16 Jan 2018 12:19:17 -0500 Received: from mail.kernel.org ([198.145.29.99]:34060 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750909AbeAPRTQ (ORCPT ); Tue, 16 Jan 2018 12:19:16 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EE81F21721 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=rostedt@goodmis.org Date: Tue, 16 Jan 2018 12:19:13 -0500 From: Steven Rostedt To: "Vladislav Valtchev (VMware)" Cc: linux-trace-devel@vger.kernel.org, linux-kernel@vger.kernel.org, y.karadz@gmail.com Subject: Re: [PATCH v3 1/3] trace-cmd: Make read_proc() to return int status via OUT arg Message-ID: <20180116121913.42d09aea@gandalf.local.home> In-Reply-To: <20180116074744.5522-2-vladislav.valtchev@gmail.com> References: <20180116074744.5522-1-vladislav.valtchev@gmail.com> <20180116074744.5522-2-vladislav.valtchev@gmail.com> X-Mailer: Claws Mail 3.14.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On Tue, 16 Jan 2018 09:47:42 +0200 "Vladislav Valtchev (VMware)" wrote: > + errno = 0; > + > + /* Read an integer from buf ignoring any non-digit trailing characters. */ > + num = strtol(buf, NULL, 10); > + > + /* strtol() returned 0: we have to check for errors */ > + if (!num && (errno == EINVAL || errno == ERANGE)) > + return -1; Repeating again here. According to the man page of strtol(): RETURN VALUE The strtol() function returns the result of the conversion, unless the value would underflow or overflow. If an underflow occurs, strtol() returns LONG_MIN. If an overflow occurs, strtol() returns LONG_MAX. In both cases, errno is set to ERANGE. Precisely the same holds for strtoll() (with LLONG_MIN and LLONG_MAX instead of LONG_MIN and LONG_MAX). and this: The implementation may also set errno to EINVAL in case no conversion was performed (no digits seen, and 0 returned). Thus, !num is not enough. The example in the man page has: errno = 0; /* To distinguish success/failure after call */ val = strtol(str, &endptr, base); /* Check for various possible errors */ if ((errno == ERANGE && (val == LONG_MAX || val == LONG_MIN)) || (errno != 0 && val == 0)) { perror("strtol"); exit(EXIT_FAILURE); } Let's follow this. -- Steve