From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from conssluserg-04.nifty.com (conssluserg-04.nifty.com [210.131.2.83]) by sourceware.org (Postfix) with ESMTPS id ADF05385DC33 for ; Fri, 5 Feb 2021 10:35:11 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org ADF05385DC33 Received: from Express5800-S70 (x067108.dynamic.ppp.asahi-net.or.jp [122.249.67.108]) (authenticated) by conssluserg-04.nifty.com with ESMTP id 115AYvXP031732 for ; Fri, 5 Feb 2021 19:34:57 +0900 DKIM-Filter: OpenDKIM Filter v2.10.3 conssluserg-04.nifty.com 115AYvXP031732 X-Nifty-SrcIP: [122.249.67.108] Date: Fri, 5 Feb 2021 19:34:57 +0900 From: Takashi Yano To: cygwin@cygwin.com Subject: Re: GDB looses pgrp setting in the terminal for debugged process after break. Message-Id: <20210205193457.cecc47a50865a59dc3f7041f@nifty.ne.jp> In-Reply-To: <20210126121402.167ba4ca0d7d8b747feede9f@nifty.ne.jp> References: <20210126121402.167ba4ca0d7d8b747feede9f@nifty.ne.jp> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.30; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-4.6 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, NICE_REPLY_A, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: cygwin@cygwin.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: General Cygwin discussions and problem reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 05 Feb 2021 10:35:15 -0000 On Tue, 26 Jan 2021 12:14:02 +0900 Takashi Yano wrote: > Hi GDB maintainer, > > In GDB, debugged process cannot continue execution after break > if it reads stdin. > > With the following steps, cat is terminated with error. > > 1) Install coreutils-debuginfo package. > 2) Run "gdb cat" in console (command prompt), not in mintty. > 3) Enter "start" in gdb. > 4) Enter "cont" in gdb. > > This results in: > /usr/bin/cat: -: Input/output error > > Both gdb-9.2-1 and gdb-10.1-1(TEST) have this problem. > > I looked into this problem and found the cause is that the pgid > setting for /usr/bin/cat is lost after break. The following patch > for GDB source resolves the issue. In the following section, > winpid is passed to getpgid() rather than cygwin pid. Also, winpid > is passed to other POSIX system calls such as kill() elsewhere. > > --- inflow.c.orig 2020-05-24 06:10:29.000000000 +0900 > +++ inflow.c 2021-01-23 17:48:27.963609500 +0900 > @@ -364,11 +364,11 @@ > #ifdef HAVE_TERMIOS_H > /* If we can't tell the inferior's actual process group, > then restore whatever was the foreground pgrp the last > time the inferior was running. See also comments > describing terminal_state::process_group. */ > -#ifdef HAVE_GETPGID > +#if defined (HAVE_GETPGID) && !defined (__CYGWIN__) > result = tcsetpgrp (0, getpgid (inf->pid)); > #else > result = tcsetpgrp (0, tinfo->process_group); > #endif > if (result == -1) > > > I hope the GDB maintainer will check it out. > > Addresses: https://cygwin.com/pipermail/cygwin-patches/2021q1/011018.html I have noticed that cygwin gdb essentially has the problem regarding terminal process group. Cygwin gdb uses CreateProcessW() to execute debugging process rather than exec(). If the debugging process is a cygwin process, cygwin pid is assigned, however, if the debugging process is a non cygwin process, cygwin pid is not assigned. Therefore, there is no appropriate process group ID to set. I wonder what is the right thing under that situation. Any idea? -- Takashi Yano