GDB looses pgrp setting in the terminal for debugged process after break.

[Takashi Yano <takashi.yano@nifty.ne.jp>]

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

-- 
Takashi Yano <takashi.yano@nifty.ne.jp>