From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Paul Eggert Newsgroups: gmane.emacs.devel Subject: Re: wait_reading_process_ouput hangs in certain cases (w/ patches) Date: Sun, 12 Nov 2017 13:17:33 -0800 Organization: UCLA Computer Science Department Message-ID: References: <83lgjz8eiy.fsf@gnu.org> <831slp98ut.fsf@gnu.org> <83tvyj62qg.fsf@gnu.org> <83r2tetf90.fsf@gnu.org> <5150d198-8dd3-9cf4-5914-b7e945294452@binary-island.eu> <83tvy7s6wi.fsf@gnu.org> <83inemrqid.fsf@gnu.org> <398f8d17-b727-d5d6-4a31-772448c7ca0d@binary-island.eu> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1510521474 13597 195.159.176.226 (12 Nov 2017 21:17:54 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 12 Nov 2017 21:17:54 +0000 (UTC) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 Cc: emacs-devel@gnu.org To: Matthias Dahl , Eli Zaretskii Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Sun Nov 12 22:17:50 2017 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1eDzdR-00035I-GR for ged-emacs-devel@m.gmane.org; Sun, 12 Nov 2017 22:17:45 +0100 Original-Received: from localhost ([::1]:51313 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eDzdZ-0003kf-0e for ged-emacs-devel@m.gmane.org; Sun, 12 Nov 2017 16:17:53 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:51860) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eDzdP-0003kO-F6 for emacs-devel@gnu.org; Sun, 12 Nov 2017 16:17:44 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eDzdO-0002le-HM for emacs-devel@gnu.org; Sun, 12 Nov 2017 16:17:43 -0500 Original-Received: from zimbra.cs.ucla.edu ([131.179.128.68]:56148) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eDzdK-0002jx-Oo; Sun, 12 Nov 2017 16:17:38 -0500 Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id DC929160FAA; Sun, 12 Nov 2017 13:17:34 -0800 (PST) Original-Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id WmvcsNOa1yr9; Sun, 12 Nov 2017 13:17:34 -0800 (PST) Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id ED44B160FB5; Sun, 12 Nov 2017 13:17:33 -0800 (PST) X-Virus-Scanned: amavisd-new at zimbra.cs.ucla.edu Original-Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id GPxfnwbSqut5; Sun, 12 Nov 2017 13:17:33 -0800 (PST) Original-Received: from [192.168.1.9] (unknown [47.154.30.119]) by zimbra.cs.ucla.edu (Postfix) with ESMTPSA id C8C38160F81; Sun, 12 Nov 2017 13:17:33 -0800 (PST) In-Reply-To: <398f8d17-b727-d5d6-4a31-772448c7ca0d@binary-island.eu> Content-Language: en-US X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [fuzzy] X-Received-From: 131.179.128.68 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.org gmane.emacs.devel:220116 Archived-At: Matthias Dahl wrote: > /* Now set NBYTES how many bytes we must decode. */ > nbytes +=3D carryover; > =20 > + p->infd_num_bytes_read +=3D nbytes; This will include the carryover in the number of bytes read, even though = this=20 code did not read the carryover bytes. Is that what you intended? > + /* Byte-count for process output read from `infd'. */ > + EMACS_UINT infd_num_bytes_read; This is overkill, as the total amount of bytes read by a call to=20 read_process_output cannot exceed 4096, so all we need is an unsigned cou= nter=20 with more than 12 bits. How about making it 'unsigned int' instead? It co= uld=20 even be 'unsigned short', though that might be overkill. Whatever size is= =20 chosen, the comment should say that the value recorded is the true value = modulo=20 the word size. > + /* Timers could have called `accept-process-output', thus re= ading the output > + of wait_proc while we (in the worst case) wait endlessly = for it to become > + available later. So we need to check if data has been rea= d and break out > + early if that is so since our job has been fulfilled. */ > + if (wait_proc > + && wait_proc->infd_num_bytes_read !=3D initial_wait_proc= _num_bytes_read) > + { > + /* Computations on unsigned types are well defined and w= on't overflow, > + so this is safe even if our initial value > our curre= nt value, in > + case of a wrap around. (ISO/IEC 9899:1999 =C2=A76.2.5= /9) */ > + got_some_output =3D wait_proc->infd_num_bytes_read > + - initial_wait_proc_num_bytes_read; > + } > + All that matters for got_some_output is whether it is negative, zero, or=20 positive. So I suggest replacing the above with the following, as it's a = bit=20 faster and simpler and doesn't require commentary: > + if (wait_proc > + && wait_proc->infd_num_bytes_read !=3D initial_wait_proc= _num_bytes_read) > + got_some_output =3D 1; Similarly for the other change that assigns to got_some_output.