Fix crash on "quit" + TUI + remote + async

[Pedro Alves]

Ahem, EWRONGPATCH.

Here is the correct one.  OK?

On Monday 28 July 2008 16:33:40, Pedro Alves wrote:
> I was debugging against a remote stub in async mode, using the TUI, and I
> issued "quit" while still connected, in the hopes of bailing out of GDB
> without much fuss, but, I ran into this SEGV:
>
> Program received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 0x7fcf597fb6e0 (LWP 13869)]
> 0x0000000000552f5e in serial_can_async_p (scb=0x0) at
> ../../src/gdb/serial.c:504 504       return (scb->ops->async != NULL);
> (top-gdb) bt
> #0  0x0000000000552f5e in serial_can_async_p (scb=0x0) at
> ../../src/gdb/serial.c:504 During symbol reading, unsupported tag:
> 'DW_TAG_const_type'.
> #1  0x000000000042ffa3 in remote_can_async_p () at
> ../../src/gdb/remote.c:8207 During symbol reading, DW_AT_type missing from
> DW_TAG_subrange_type. #2  0x000000000040d740 in execute_command
> (p=0x7fff618212a0 "set width 118", from_tty=0) at ../../src/gdb/top.c:382
> #3  0x0000000000457d1c in tui_update_gdb_sizes () at
> ../../src/gdb/tui/tui-win.c:468 #4  0x0000000000452002 in tui_disable () at
> ../../src/gdb/tui/tui.c:455 #5  0x0000000000452581 in tui_exit () at
> ../../src/gdb/tui/tui-interp.c:45 #6  0x00007fcf589e0110 in exit () from
> /lib/libc.so.6
> #7  0x000000000040edeb in quit_force (args=0x0, from_tty=1) at
> ../../src/gdb/top.c:1292 #8  0x0000000000443f20 in quit_command (args=0x0,
> from_tty=1) at ../../src/gdb/cli/cli-cmds.c:315 #9  0x000000000043e660 in
> do_cfunc (c=0xa344b0, args=0x0, from_tty=1) at
> ../../src/gdb/cli/cli-decode.c:60 #10 0x00000000004412a3 in cmd_func
> (cmd=0xa344b0, args=0x0, from_tty=1) at ../../src/gdb/cli/cli-decode.c:1680
> #11 0x000000000040d9df in execute_command (p=0x9e81c1 "", from_tty=1) at
> ../../src/gdb/top.c:465 #12 0x00000000004c19ea in command_handler
> (command=0x9e81c0 "q") at ../../src/gdb/event-top.c:514
>
> As you can see from from #2, disabling the tui ends up
> executing a command.  At this point, the remote target was still
> pushed on the stack, but it had already been closed, hence the remote
> connection was closed, and remote_desc was == NULL.
>
> There are target_can_async_p call around every command invocation,
> and since the remote target was still on the stack, remote_can_async_p
> was called, but it isn't expecting to be reached with remote_desc == NULL,
> as most of remote's code:
>
>  static int
>  remote_can_async_p (void)
>  {
>    if (!remote_async_permitted)
>      /* We only enable async when the user specifically asks for it.  */
>      return 0;
>
>    /* We're async whenever the serial device is.  */
>    return remote_async_mask_value && serial_can_async_p (remote_desc);
>  }
>
> The issue is that quit_target closes the current target, but doesn't
> pop it:
>
>  static int
>  quit_target (void *arg)
>  {
>    struct qt_args *qt = (struct qt_args *)arg;
>
>    if (! ptid_equal (inferior_ptid, null_ptid) && target_has_execution)
>      {
>        if (attach_flag)
>          target_detach (qt->args, qt->from_tty);
>        else
>          target_kill ();
>      }
>
>    /* UDI wants this, to kill the TIP.  */
>    target_close (&current_target, 1);
>
>    /* Save the history information if it is appropriate to do so.  */
>    if (write_history_p && history_filename)
>      write_history (history_filename);
>
>    do_final_cleanups (ALL_CLEANUPS);	/* Do any final cleanups before
> exiting */
>
>    return 0;
>  }
>
>
> The UDI target seems to be gone from the sources, but, even if it's still
> here and I missed it, this is broken.  It should at best be a pop_target. 
> But, while I'm at it, if the current target is of stratum >
> process_stratum, this will still leave the process_stratum target open,
> which is much
> more likelly to need closing.  So, I've come up with a new
> pop_all_targets method and used it instead.
>
> Tested against x86_64-unknown-linux-gnu native and gdbserver.
>
> OK?

-- 
Pedro Alves
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