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[Bug gdb/20494] User input stops being echoed in CLI


https://sourceware.org/bugzilla/show_bug.cgi?id=20494

--- Comment #10 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Pedro Alves <palves@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=d9de1fe3d5607f96491e8f16f474b9441cbec849

commit d9de1fe3d5607f96491e8f16f474b9441cbec849
Author: Pedro Alves <palves@redhat.com>
Date:   Tue Aug 23 16:03:28 2016 +0100

    Fix PR20494 - User input stops being echoed in CLI

    This patch fixes a problem that problem triggers if you start an
    inferior, e.g., with the "start" command, in a UI created with the
    new-ui command, and then run a foreground execution command in the
    main UI.  Once the program stops for the latter command, typing in the
    main UI no longer echoes back to the user.

    The problem revolves around this:

    - gdb_has_a_terminal computes its result lazily, on first call.

      that is what saves gdb's initial main UI terminal state (the UI
      associated with stdin):

              our_terminal_info.ttystate = serial_get_tty_state (stdin_serial);

      This is the state that target_terminal_ours() restores.

    - In this scenario, the gdb_has_a_terminal function happens to be
      first ever called from within the target_terminal_init call in
      startup_inferior:

          (top-gdb) bt
          #0  gdb_has_a_terminal () at src/gdb/inflow.c:157
          #1  0x000000000079db22 in child_terminal_init_with_pgrp () at
src/gdb/inflow.c:217
           [...]
          #4  0x000000000065bacb in target_terminal_init () at
src/gdb/target.c:456
          #5  0x00000000004676d2 in startup_inferior () at
src/gdb/fork-child.c:531
           [...]
          #7  0x000000000046b168 in linux_nat_create_inferior () at
src/gdb/linux-nat.c:1112
           [...]
          #9  0x00000000005f20c9 in start_command (args=0x0, from_tty=1) at
src/gdb/infcmd.c:657

    If the command to start the inferior is issued on the main UI, then
    readline will have deprepped the terminal when we reach the above, and
    the problem doesn't appear.

    If however the command is issued on a non-main UI, then when we reach
    that gdb_has_a_terminal call, the main UI's terminal state is still
    set to whatever readline has sets it to in rl_prep_terminal, which
    happens to have echo disabled.  Later, when the following synchronous
    execution command finishes, we'll call target_terminal_ours to restore
    gdb's the main UI's terminal settings, and that restores the terminal
    state with echo disabled...

    Conceptually, the fix is to move the gdb_has_a_terminal call earlier,
    to someplace during GDB initialization, before readline/ncurses have
    had a chance to change terminal settings.  Turns out that
    "set_initial_gdb_ttystate" is exactly such a place.

    I say conceptually, because the fix actually inlines the
    gdb_has_a_terminal part that saves the terminal state in
    set_initial_gdb_ttystate and then simplifies gdb_has_a_terminal, since
    there's no point in making gdb_has_a_terminal do lazy computation.

    gdb/ChangeLog:
    2016-08-23  Pedro Alves  <palves@redhat.com>

        PR gdb/20494
        * inflow.c (our_terminal_info, initial_gdb_ttystate): Update
        comments.
        (enum gdb_has_a_terminal_flag_enum, gdb_has_a_terminal_flag):
        Delete.
        (set_initial_gdb_ttystate): Record our_terminal_info here too,
        instead of ...
        (gdb_has_a_terminal): ... here.  Reimplement in terms of
        initial_gdb_ttystate.  Make static.
        * terminal.h (gdb_has_a_terminal): Delete declaration.
        (set_initial_gdb_ttystate): Add comment.
        * top.c (show_interactive_mode): Use input_interactive_p instead
        of gdb_has_a_terminal.

    gdb/testsuite/ChangeLog:
    2016-08-23  Pedro Alves  <palves@redhat.com>

        PR gdb/20494
        * gdb.base/new-ui-echo.c: New file.
        * gdb.base/new-ui-echo.exp: New file.

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