http://sourceware.org/ml/gdb-patches/2015-10/msg00301.html

Subject: [PATCH 1/3] Never kill PID on: gdb exec PID

Hi,

in some cases with deleted main executable GDB will want to kill the inferior.

$ cp /bin/sleep /tmp/sleep;/tmp/sleep 1h&p=$!

$ rm /tmp/sleep

$ gdb /tmp/sleep $p

GNU gdb (GDB) 7.10.50.20151016-cvs

/tmp/sleep: No such file or directory.

Attaching to process 9694

/tmp/sleep (deleted): No such file or directory.

A program is being debugged already.  Kill it? (y or n) _

The first attachment of "/tmp/sleep" commandline argument errors at:

#0  throw_error (error=GENERIC_ERROR, fmt=0x116d135 "%s.") at ./common/common-exceptions.c:371

#1  in throw_perror_with_name (errcode=GENERIC_ERROR, string=0x7fffffffdb96 "/dfsfds") at utils.c:974

#2  in perror_with_name (string=0x7fffffffdb96 "/dfsfds") at utils.c:982

#3  in exec_file_attach (filename=0x7fffffffdb96 "/dfsfds", from_tty=1) at exec.c:268

267               if (scratch_chan < 0)

268                 perror_with_name (filename);

#4  in catch_command_errors_const (command=0x80f59f <exec_file_attach>, arg=0x7fffffffdb96 "/dfsfds", from_tty=1) at main.c:395

#5  in captured_main (data=0x7fffffffd6f0) at main.c:1051

1051          if (catch_command_errors_const (exec_file_attach, execarg,

1052                                          !batch_flag))

Then GDB tries to attach to the process $p:

#0  inferior_appeared (inf=0x240e0b0, pid=29210) at inferior.c:305

#1  in inf_ptrace_attach (ops=0x2339540, args=0x21dcdc0 "29210", from_tty=1) at inf-ptrace.c:206

#2  in linux_nat_attach (ops=0x2339540, args=0x21dcdc0 "29210", from_tty=1) at linux-nat.c:1278

#3  in attach_command (args=0x21dcdc0 "29210", from_tty=1) at infcmd.c:2748

#4  in catch_command_errors (command=0x79d7e5 <attach_command>, arg=0x7fffffffdb9e "29210", from_tty=1) at main.c:368

#5  in captured_main (data=0x7fffffffd6f0) at main.c:1082

1082              if (catch_command_errors (attach_command, pid_or_core_arg,

1083                                        !batch_flag) == 0)

This succeeds and since this moment GDB has a valid inferior.  But despite that

the lines

1082              if (catch_command_errors (attach_command, pid_or_core_arg,

1083                                        !batch_flag) == 0)

still fail because consequently attach_command() fails to find the associated

executable file:

#0  throw_error (error=GENERIC_ERROR, fmt=0x116d135 "%s.") at ./common/common-exceptions.c:371

#1  in throw_perror_with_name (errcode=GENERIC_ERROR, string=0x2477860 "/tmp/sleep (deleted)") at utils.c:974

#2  in perror_with_name (string=0x2477860 "/tmp/sleep (deleted)") at utils.c:982

#3  in exec_file_attach (filename=0x2477860 "/tmp/sleep (deleted)", from_tty=1) at exec.c:268

267               if (scratch_chan < 0)

268                 perror_with_name (filename);

#4  in exec_file_locate_attach (pid=29210, from_tty=1) at exec.c:173

#5  in attach_command_post_wait (args=0x24739b0 "29210", from_tty=1, async_exec=0) at infcmd.c:2628

#6  in attach_command_continuation (args=0x2473590, err=0) at infcmd.c:2700

#7  in do_my_continuations_1 (pmy_chain=0x7fffffffd190, err=0) at continuations.c:59

#8  in do_my_continuations (list=0x240e130, err=0) at continuations.c:83

#9  in do_all_inferior_continuations (err=0) at continuations.c:125

#10 in inferior_event_handler (event_type=INF_EXEC_COMPLETE, client_data=0x0) at inf-loop.c:60

#11 in fetch_inferior_event (client_data=0x0) at infrun.c:3929

#12 in inferior_event_handler (event_type=INF_REG_EVENT, client_data=0x0) at inf-loop.c:44

#13 in handle_target_event (error=0, client_data=0x0) at linux-nat.c:4681

#14 in handle_file_event (file_ptr=0x21e4170, ready_mask=1) at event-loop.c:708

#15 in gdb_wait_for_event (block=0) at event-loop.c:834

#16 in gdb_do_one_event () at event-loop.c:298

#17 in wait_sync_command_done () at top.c:373

#18 in maybe_wait_sync_command_done (was_sync=0) at top.c:388

#19 in catch_command_errors (command=0x79d7e5 <attach_command>, arg=0x7fffffffdb9e "29210", from_tty=1) at main.c:370

#20 in captured_main (data=0x7fffffffd6f0) at main.c:1082

1082              if (catch_command_errors (attach_command, pid_or_core_arg,

1083                                        !batch_flag) == 0)

and therefore GDB executes the following:

(gdb) bt

#5  in query (ctlstr=0x1141ae8 "A program is being debugged already.  Kill it? ") at utils.c:1371

#6  in target_preopen (from_tty=1) at target.c:2183

2179	  if (have_inferiors ())

2180	    {

2181	      if (!from_tty

2182		  || !have_live_inferiors ()

2183		  || query (_("A program is being debugged already.  Kill it? ")))

2184		iterate_over_inferiors (dispose_inferior, NULL);

2185	      else

2186		error (_("Program not killed."));

2187	    }

#7  in core_open (arg=0x7fffffffdb9f "9694", from_tty=1) at corelow.c:283

#8  in core_file_command (filename=0x7fffffffdb9f "9694", from_tty=1) at corefile.c:77

#9  in catch_command_errors (command=0x86ca16 <core_file_command>, arg=0x7fffffffdb9f "9694", from_tty=1) at main.c:368

#10 in captured_main (data=0x7fffffffd6f0) at main.c:1084

1084		    catch_command_errors (core_file_command, pid_or_core_arg,

1085					  !batch_flag);

No regressions on {x86_64,x86_64-m32,i686}-fedora24pre-linux-gnu.

Thanks,

Jan

gdb/ChangeLog

2015-10-16  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* main.c (captured_main): Run core_file_command for pid_or_core_arg

	only if not have_inferiors ().

gdb/testsuite/ChangeLog

2015-10-16  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gdb.base/attach-kills.c: New.

	* gdb.base/attach-kills.exp: New.

---

 gdb/testsuite/gdb.base/attach-kills.c   |   25 ++++++++++++++++

 gdb/testsuite/gdb.base/attach-kills.exp |   49 +++++++++++++++++++++++++++++++

 2 files changed, 74 insertions(+)

 create mode 100644 gdb/testsuite/gdb.base/attach-kills.c

 create mode 100644 gdb/testsuite/gdb.base/attach-kills.exp

Index: gdb-7.2/gdb/main.c

===================================================================

--- gdb-7.2.orig/gdb/main.c	2015-10-16 22:53:14.000000000 +0200

+++ gdb-7.2/gdb/main.c	2015-10-16 22:53:58.840722140 +0200

@@ -975,7 +975,10 @@ Can't attach to process and specify a co

       if (isdigit (pid_or_core_arg[0]))

 	{

 	  if (catch_command_errors (attach_command, pid_or_core_arg,

-				    !batch_flag, RETURN_MASK_ALL) == 0)

+				    !batch_flag, RETURN_MASK_ALL) == 0

+	      /* attach_command could succeed partially and core_file_command

+		 would try to kill it.  */

+	      && !have_inferiors ())

 	    catch_command_errors (core_file_command, pid_or_core_arg,

 				  !batch_flag, RETURN_MASK_ALL);

 	}

Index: gdb-7.2/gdb/testsuite/gdb.base/attach-kills.c

===================================================================

--- /dev/null	1970-01-01 00:00:00.000000000 +0000

+++ gdb-7.2/gdb/testsuite/gdb.base/attach-kills.c	2015-10-16 22:53:22.843486331 +0200

@@ -0,0 +1,25 @@

+/* This testcase is part of GDB, the GNU debugger.

+

+   Copyright 2015 Free Software Foundation, Inc.

+

+   This program is free software; you can redistribute it and/or modify

+   it under the terms of the GNU General Public License as published by

+   the Free Software Foundation; either version 3 of the License, or

+   (at your option) any later version.

+

+   This program is distributed in the hope that it will be useful,

+   but WITHOUT ANY WARRANTY; without even the implied warranty of

+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

+   GNU General Public License for more details.

+

+   You should have received a copy of the GNU General Public License

+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

+

+#include <unistd.h>

+

+int

+main (void)

+{

+  sleep (600);

+  return 0;

+}

Index: gdb-7.2/gdb/testsuite/gdb.base/attach-kills.exp

===================================================================

--- /dev/null	1970-01-01 00:00:00.000000000 +0000

+++ gdb-7.2/gdb/testsuite/gdb.base/attach-kills.exp	2015-10-16 23:02:33.791095444 +0200

@@ -0,0 +1,39 @@

+# Copyright (C) 2015 Free Software Foundation, Inc.

+#

+# This program is free software; you can redistribute it and/or modify

+# it under the terms of the GNU General Public License as published by

+# the Free Software Foundation; either version 3 of the License, or

+# (at your option) any later version.

+#

+# This program is distributed in the hope that it will be useful,

+# but WITHOUT ANY WARRANTY; without even the implied warranty of

+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

+# GNU General Public License for more details.

+#

+# You should have received a copy of the GNU General Public License

+# along with this program.  If not, see <http://www.gnu.org/licenses/>.

+

+set testfile attach-kills

+set binfile ${objdir}/${subdir}/${testfile}

+

+if { [build_executable ${testfile}.exp $testfile] == -1 } {

+    return -1

+}

+

+# Start the program running and then wait for a bit, to be sure

+# that it can be attached to.

+

+set testpid [eval exec $binfile &]

+exec sleep 2

+

+remote_exec target "cp -pf -- $binfile $binfile-copy"

+remote_exec target "rm -f -- $binfile"

+

+set GDBFLAGS_orig $GDBFLAGS

+set GDBFLAGS "$GDBFLAGS /DoEsNoTeXySt $testpid"

+gdb_start

+set GDBFLAGS $GDBFLAGS_orig

+

+gdb_test "info inferiors" " process \[0-9\].*"

+

+remote_exec build "kill -9 ${testpid}"