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

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:

267               if (scratch_chan < 0)
268                 perror_with_name (filename);
1051          if (catch_command_errors_const (exec_file_attach, execarg,
1052                                          !batch_flag))

Then GDB tries to attach to the process $p:

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:

267               if (scratch_chan < 0)
268                 perror_with_name (filename);
1082              if (catch_command_errors (attach_command, pid_or_core_arg,
1083                                        !batch_flag) == 0)

and therefore GDB executes the following:

(gdb) bt
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	    }
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.

diff --git a/gdb/main.c b/gdb/main.c
--- a/gdb/main.c
+++ b/gdb/main.c
@@ -1115,7 +1115,10 @@ captured_main_1 (struct captured_main_args *context)
       if (isdigit (pid_or_core_arg[0]))
 	{
 	  if (catch_command_errors (attach_command, pid_or_core_arg,
-				    !batch_flag) == 0)
+				    !batch_flag) == 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);
 	}