Do not send queries on secondary UIs

This is a follow-up to

  https://sourceware.org/ml/gdb-patches/2017-02/msg00261.html

This patch restricts queries to the main UI, which allows to avoid two
different problems.

The first one is that GDB is issuing queries on secondary MI channels
for which a TTY is allocated.  The second one is that GDB is not able to
handle queries on two (CLI) UIs simultaneously.  Restricting queries to
the main UI allows to bypass these two problems.

More details on how/why these two problems happen:

1. Queries on secondary MI UI

  The current criterion to decide if we should query the user is whether
  the input stream is a TTY.  The original way to start GDB in MI mode
  from a front-end was to create a subprocess with pipes to its
  stdin/stdout.  In this case, the input was considered non-interactive
  and queries were auto-answered.  Now that front-ends can create the MI
  channel as a separate UI connected to a dedicated TTY, GDB now
  considers this input stream as interactive and sends queries to it.
  By restricting queries to the main UI, we make sure we never query on
  the secondary MI UI.

2. Simultaneous queries

  As Pedro stated it, when you have two queries on two different CLI UIs
  at the same time, you end up with the following pseudo stack:

  #0 gdb_readline_wrapper
  #1 defaulted_query                 // for UI #2
  #2 handle_command
  #3 execute_command ("handle SIGTRAP" ....
  #4 stdin_event_handler             // input on UI #2
  #5 gdb_do_one_event
  #7 gdb_readline_wrapper
  #8 defaulted_query                 // for UI #1
  #9 handle_command
  #10 execute_command ("handle SIGINT" ....
  #11 stdin_event_handler            // input on UI #1
  #12 gdb_do_one_event
  #13 gdb_readline_wrapper

  trying to answer the query on UI #1 will therefore answer for UI #2.

  By restricting the queries to the main UI, we ensure that there will
  never be more than one pending query, since you can't have two queries
  on a UI at the same time.

I added a snippet to gdb.base/new-ui.exp to verify that we get a query
on the main UI, but that we don't on the secondary one (or, more
precisely, that it gets auto-answered).

gdb/ChangeLog:

	* utils.c (defaulted_query): Don't query on secondary UIs.

gdb/testsuite/ChangeLog:

	* gdb.base/new-ui.exp (do_test): Test queries behavior on main
	and extra UIs.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index dbee02a3fc2826fc82216f22669423aaf852680d..dcd047a04640d136161e9fb8071ed2ba4f815543 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,7 @@
+2017-02-10  Simon Marchi  <simon.marchi@ericsson.com>
+
+       * utils.c (defaulted_query): Don't query on secondary UIs.
+
 2017-02-10  Tom Tromey  <tom@tromey.com>
 
        * rust-lang.c (rust_get_disr_info): Remove unused variable.

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 3274b405165527922bca3ca5575219ce17bc78d2..c1e53b77a0fa792e099d6f9f2471bd730a0aaf78 100644 (file)
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2017-02-10  Simon Marchi  <simon.marchi@ericsson.com>
+
+       * gdb.base/new-ui.exp (do_test): Test queries behavior on main
+       and extra UIs.
+
 2017-02-10  Simon Marchi  <simon.marchi@ericsson.com>
 
        * gdb.base/new-ui.exp (do_test, do_test_invalid_args): Use

diff --git a/gdb/testsuite/gdb.base/new-ui.exp b/gdb/testsuite/gdb.base/new-ui.exp
index 8224b7d6154a5276b099f81e83a027f859e0b361..b84f4de712c3a99db55e3e62a7a1eae3d596977a 100644 (file)
--- a/gdb/testsuite/gdb.base/new-ui.exp
+++ b/gdb/testsuite/gdb.base/new-ui.exp
@@ -128,6 +128,18 @@ proc_with_prefix do_test {} {
        gdb_test "print 2" "^print 2\r\n\\\$2 = 2" "print on extra console"
     }
 
+    # Verify that we get proper queries on the main UI, but that they are
+    # auto-answered on secondary UIs.
+    with_spawn_id $gdb_main_spawn_id {
+       gdb_test "delete" "" "delete all breakpoint on main console" \
+                "Delete all breakpoints. .y or n. $" "n"
+    }
+    with_spawn_id $extra_spawn_id {
+       gdb_test "delete" \
+                "Delete all breakpoints. .y or n. .answered Y; input not from terminal." \
+                "delete all breakpoints on extra console"
+    }
+
     # Run a few execution tests with the main console as the driver
     # console.
     with_test_prefix "main console" {

diff --git a/gdb/utils.c b/gdb/utils.c
index 3dc2f03d61dd0e02aa16685f77dc048e1b00ff55..27021a1d458329c4552aef3b1a7951198d8c27e1 100644 (file)
--- a/gdb/utils.c
+++ b/gdb/utils.c
@@ -1175,7 +1175,9 @@ defaulted_query (const char *ctlstr, const char defchar, va_list args)
      way, important error messages don't get lost when talking to GDB
      over a pipe.  */
   if (current_ui->instream != current_ui->stdin_stream
-      || !input_interactive_p (current_ui))
+      || !input_interactive_p (current_ui)
+      /* Restrict queries to the main UI.  */
+      || current_ui != main_ui)
     {
       old_chain = make_cleanup_restore_target_terminal ();