Fix gdb.threads/process-dies-while-detaching.exp

I noticed [1] a test bug in gdb.threads/process-dies-while-detaching.exp.
Simplified, the test code in question looks somewhat like this:

~~~
  # Detach from a process, and ensure that it exits after detaching.
  # This relies on inferior I/O.

  proc detach_and_expect_exit {test} {

      gdb_test_multiple "detach" $test ....

      set saw_prompt 0
      set saw_inf_exit 0
      while { !$saw_prompt && !$saw_inf_exit } {
          gdb_test_multiple "" $test {
              -re "exited, status=0" {
                  set saw_inf_exit 1
              }
              -re "$gdb_prompt " {
                  set saw_prompt 1
              }
          }
      }

      pass $test
  }
~~~

The bug is in the while loop's condition.  We want to make sure we see
both the inferior output and the prompt, so the loop's test should be:

   -    while { !$saw_prompt && !$saw_inf_exit } {
   +    while { !$saw_prompt || !$saw_inf_exit } {

If we just fix that, the test starts failing though, because it
exposes a couple latent problems:

- When called from test_detach_killed_outside, the parent doesn't
  print "exited, status=0", because in that case the child dies with a
  signal, and so detach_and_expect_exit times out.

  Fix it by making the parent print "signaled, sig=9" in that case,
  and have the .exp expect it.

- When testing against --target_board=native-gdbserver, sometimes we'd
  get this:

    ERROR: Process no longer exists
    ERROR: : spawn id exp9 not open
	while executing
    "expect {
    -i exp8 -timeout 220
	    -i $server_spawn_id
	    eof {
		pass $test
		wait -i $server_spawn_id
		unset server_spawn_id
	    }
	    timeout {
	       ..."
	("uplevel" body line 1)
	invoked from within
    "uplevel $body" NONE : spawn id exp9 not open

  The problem is that:

   - inferior_spawn_id and server_spawn_id are the same when testing
     with gdbserver.
   - gdbserver exits after "detach", so we get an eof for
     $inferior_spawn_id in the loop in detach_and_expect_exit.
     That's the first "ERROR: Process no longer exists".
   - and then when we reach test_server_exit, server_spawn_id
     is already closed (because server_spawn_id==inferior_spawn_id).

  To handle this, make the loop in detach_and_expect_exit use an
  indirect spawn id list and remove $inferior_spawn_id from the list
  as soon as we got the inferior output we're expecting, so that the
  "eof" is left unprocessed until we reach test_server_exit.

[1] I changed GDB in a way that should have made the test fail, but it
    didn't.

gdb/testsuite/ChangeLog:
2017-12-03  Pedro Alves  <palves@redhat.com>

	* gdb.threads/process-dies-while-detaching.c: Include <errno.h>
	and <string.h>.
	(parent_function): Print distinct messages when waitpid fails, or
	the child exits with a signal, or the child exits for an unhandled
	reason.
	* gdb.threads/process-dies-while-detaching.exp
	(detach_and_expect_exit): New 'inf_output_re' parameter and use
	it.  Wait for both inferior output and GDB's prompt.  Use an
	indirect spawn id list.
	(do_detach): New parameter 'child_exit'.  Use it to compute
	expected inferior output.
	(test_detach, test_detach_watch, test_detach_killed_outside):
	Adjust to pass down the expected child exit kind.

3 files changed, 71 insertions, 22 deletions

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 779fd0a..fa096b3 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,19 @@
+2017-12-03  Pedro Alves  <palves@redhat.com>
+
+	* gdb.threads/process-dies-while-detaching.c: Include <errno.h>
+	and <string.h>.
+	(parent_function): Print distinct messages when waitpid fails, or
+	the child exits with a signal, or the child exits for an unhandled
+	reason.
+	* gdb.threads/process-dies-while-detaching.exp
+	(detach_and_expect_exit): New 'inf_output_re' parameter and use
+	it.  Wait for both inferior output and GDB's prompt.  Use an
+	indirect spawn id list.
+	(do_detach): New parameter 'child_exit'.  Use it to compute
+	expected inferior output.
+	(test_detach, test_detach_watch, test_detach_killed_outside):
+	Adjust to pass down the expected child exit kind.
+
 2017-12-01  Joel Brobecker  <brobecker@adacore.com>
 	    Sergio Durigan Junior  <sergiodj@redhat.com>
 	    Pedro Alves  <palves@redhat.com>
diff --git a/gdb/testsuite/gdb.threads/process-dies-while-detaching.c b/gdb/testsuite/gdb.threads/process-dies-while-detaching.c
index eecaaed..4ba50d4 100644
--- a/gdb/testsuite/gdb.threads/process-dies-while-detaching.c
+++ b/gdb/testsuite/gdb.threads/process-dies-while-detaching.c
@@ -22,6 +22,8 @@
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <assert.h>
+#include <errno.h>
+#include <string.h>
 
 /* This barrier ensures we only reach the initial breakpoint after all
    threads have started.  */
@@ -78,15 +80,27 @@ parent_function (pid_t child)
   alarm (300);
 
   ret = waitpid (child, &status, 0);
+
   if (ret == -1)
-    exit (1);
-  else if (!WIFEXITED (status))
-    exit (2);
-  else
+    {
+      printf ("waitpid, errno=%d (%s)\n", errno, strerror (errno));
+      exit (1);
+    }
+  else if (WIFEXITED (status))
     {
       printf ("exited, status=%d\n", WEXITSTATUS (status));
       exit (0);
     }
+  else if (WIFSIGNALED (status))
+    {
+      printf ("signaled, sig=%d\n", WTERMSIG (status));
+      exit (2);
+    }
+  else
+    {
+      printf ("unexpected, status=%x\n", status);
+      exit (3);
+    }
 }
 
 #endif
diff --git a/gdb/testsuite/gdb.threads/process-dies-while-detaching.exp b/gdb/testsuite/gdb.threads/process-dies-while-detaching.exp
index 4cba80c..910e786 100644
--- a/gdb/testsuite/gdb.threads/process-dies-while-detaching.exp
+++ b/gdb/testsuite/gdb.threads/process-dies-while-detaching.exp
@@ -72,9 +72,10 @@ proc return_if_fail { result } {
 }
 
 # Detach from a process, and ensure that it exits after detaching.
-# This relies on inferior I/O.
+# This relies on inferior I/O.  INF_OUTPUT_RE is the pattern that
+# matches the expected inferior output.
 
-proc detach_and_expect_exit {test} {
+proc detach_and_expect_exit {inf_output_re test} {
     global decimal
     global gdb_spawn_id
     global inferior_spawn_id
@@ -85,9 +86,17 @@ proc detach_and_expect_exit {test} {
 	}
     }]
 
+    # Use an indirect spawn id list, and remove inferior spawn id from
+    # the expected output as soon as it matches, so that if
+    # $inf_inferior_spawn_id is $server_spawn_id and we're testing in
+    # "target remote" mode, the eof caused by gdbserver exiting is
+    # left for the caller to handle.
+    global daee_spawn_id_list
+    set daee_spawn_id_list "$inferior_spawn_id $gdb_spawn_id"
+
     set saw_prompt 0
     set saw_inf_exit 0
-    while { !$saw_prompt && ! $saw_inf_exit } {
+    while { !$saw_prompt || ! $saw_inf_exit } {
 	# We don't know what order the interesting things will arrive in.
 	# Using a pattern of the form 'x|y|z' instead of -re x ... -re y
 	# ... -re z ensures that expect always chooses the match that
@@ -95,14 +104,16 @@ proc detach_and_expect_exit {test} {
 	# first in the script that occurs anywhere in the input, so that
 	# we don't skip anything.
 	return_if_fail [gdb_test_multiple "" $test {
-	    -i "$inferior_spawn_id $gdb_spawn_id"
-	    -re "(exited, status=0)|($gdb_prompt )" {
+	    -i daee_spawn_id_list
+	    -re "($inf_output_re)|($gdb_prompt )" {
 		if {[info exists expect_out(1,string)]} {
 		    verbose -log "saw inferior exit"
 		    set saw_inf_exit 1
+		    set daee_spawn_id_list "$gdb_spawn_id"
 		} elseif {[info exists expect_out(2,string)]} {
 		    verbose -log "saw prompt"
 		    set saw_prompt 1
+		    set daee_spawn_id_list "$inferior_spawn_id"
 		}
 		array unset expect_out
 	    }
@@ -130,15 +141,28 @@ proc continue_to_exit_bp {} {
 #
 # CMD indicates what to do with the parent after detaching the child.
 # Can be either "detach" to detach, or "continue", to continue to
-# exit.  If "continue", then CONTINUE_RE is the regexp to expect.
-# Defaults to normal exit output.
+# exit.
+#
+# CHILD_EXIT indicates how is the child expected to exit.  Can be
+# either "normal" for normal exit, or "signal" for killed with signal
+# SIGKILL.
 #
-proc do_detach {multi_process cmd {continue_re ""}} {
+proc do_detach {multi_process cmd child_exit} {
     global decimal
     global server_spawn_id
 
-    if {$continue_re == ""} {
+    if {$child_exit == "normal"} {
 	set continue_re "exited normally.*"
+	set inf_output_re "exited, status=0"
+    } elseif {$child_exit == "signal"} {
+	if {$multi_process} {
+	    set continue_re "exited with code 02.*"
+	} else {
+	    set continue_re "terminated with signal SIGKILL.*"
+	}
+	set inf_output_re "signaled, sig=9"
+    } else {
+	error "unhandled \$child_exit: $child_exit"
     }
 
     set is_remote [expr {[target_info exists gdb_protocol]
@@ -154,7 +178,7 @@ proc do_detach {multi_process cmd {continue_re ""}} {
 	if {$cmd == "detach"} {
 	    # Make sure that detach works and that the parent process
 	    # exits cleanly.
-	    detach_and_expect_exit "detach parent"
+	    detach_and_expect_exit $inf_output_re "detach parent"
 	} elseif {$cmd == "continue"} {
 	    # Make sure that continuing works and that the parent process
 	    # exits cleanly.
@@ -205,7 +229,7 @@ proc test_detach {multi_process cmd} {
 	# Run to _exit in the child.
 	continue_to_exit_bp
 
-	do_detach $multi_process $cmd
+	do_detach $multi_process $cmd "normal"
     }
 }
 
@@ -240,7 +264,7 @@ proc test_detach_watch {multi_process cmd} {
 	# thread individually).
 	continue_to_exit_bp
 
-	do_detach $multi_process $cmd
+	do_detach $multi_process $cmd "normal"
     }
 }
 
@@ -279,12 +303,7 @@ proc test_detach_killed_outside {multi_process cmd} {
 	# Give it some time to die.
 	sleep 2
 
-	if {$multi_process} {
-	    set continue_re "exited with code 02.*"
-	} else {
-	    set continue_re "terminated with signal SIGKILL.*"
-	}
-	do_detach $multi_process $cmd $continue_re
+	do_detach $multi_process $cmd "signal"
     }
 }