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Re: Can I use -exec-interrupt to stop the inferior program?


Hello GDB developers and users!

I asked this question some time ago (in May 2006), and I implemented a solution
for Unix (it is based on signal), but I still cannot find a good solution for Windows.
Here is my original question:


I'm looking for a solution how to stop the inferior program,
which is running under gdb. I can stop it using ^C, but I
need a solution, that will work for the following case
on Windows (Cygwin):

Java application
      |   ^
stdin |   | stdout
      v   |
GDB debugger (gdb --i mi --tty /dev/pts/2 ...)
      |  ^
      v  |
Inferior program  <--> External terminal (/dev/pts/28)


The action to stop the program is initiated by Java application, which cannot send ^C to the external terminal.


Nick Roberts suggested to use signals to implement "interrupt" action,
and it really works very well on Unix (Solaris and Linux), but unfortunately
it does not work properly on Windows. If I send SIGTSTP, gdb does not
show that the program is stopped (and it really does not stop), so it looks
like this signal is ignored. If I send SIGINT, the program is really interrupted,
but it seems to cause SIGSEGV (Segmentation Fault), and there is no way
to continue the debugging. Here is a scenario (I use Cygwin):


Window 1: start debugging, set breakpoint, continue
===================================
$ gdb --i mi
~"GNU gdb 6.5.50.20060706-cvs (cygwin-special)\n"
~"Copyright (C) 2006 Free Software Foundation, Inc.\n"
~"GDB is free software, covered by the GNU General Public License, and you are\n"
~"welcome to change it and/or distribute copies of it under certain conditions.\n"
~"Type \"show copying\" to see the conditions.\n"
~"There is absolutely no warranty for GDB. Type \"show warranty\" for details.\n"
~"This GDB was configured as \"i686-pc-cygwin\"."
~"\n"
(gdb)
-file-exec-and-symbols C:/tmp/nikm/samples/LongLoop1/dist/Debug/GNU-Windows/longloop1
^done
(gdb)
-break-insert main
^done,bkpt={number="1",type="breakpoint",disp="keep",enabled="y",addr="0x004011b
5",func="main",file="main.cc",fullname="/cygdrive/c/tmp/nikm/samples/LongLoop1/m
ain.cc",line="33",times="0"}
(gdb)
-exec-run
^running
(gdb)
*stopped,reason="breakpoint-hit",bkptno="1",thread-id="1",frame={addr="0x004011b
5",func="main",args=[{name="argc",value="1"},{name="argv",value="0x6c1f50"}],fil
e="main.cc",fullname="/cygdrive/c/tmp/nikm/samples/LongLoop1/main.cc",line="33"}
(gdb)
-exec-continue
^running
(gdb)



Window 2: send signal
===============
$ ps
PID PPID PGID WINPID TTY UID STIME COMMAND
1520 1 1520 1520 con 1005 23:22:26 /usr/bin/bash
884 1 884 884 con 1005 23:23:47 /usr/bin/bash
1832 1520 1832 3880 con 1005 23:24:17 /usr/bin/gdb
4036 1 4036 4036 con 1005 23:27:14 /cygdrive/c/tmp/nikm/sam
ples/LongLoop1/dist/Debug/GNU-Windows/longloop1
2380 884 2380 2336 con 1005 23:27:16 /usr/bin/ps


$ kill -INT 4036


Window 1: caught signal ================= ~"\n" ~"[Switching to thread 4036.0x784]\n" *stopped,reason="signal-received",signal-name="SIGSEGV",signal-meaning="Segmenta tion fault",thread-id="2",frame={addr="0x000007d4",func="??",args=[]} (gdb)

After that there is no way to continue:
=========================
-exec-continue
^running
(gdb)
*stopped,reason="signal-received",signal-name="SIGSEGV",signal-meaning="Segmenta
tion fault",thread-id="2",frame={addr="0x000007d4",func="??",args=[]}
(gdb)

Could you please tell me if there any other way to interrupt program on Windows,
so that gdb will show where it is stopped, and will allow to continue?


Thanks in advance,
Nikolay Molchanov




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