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72994b6028
PR26056 reports that when GDB is connected to non-TTY stdin/stdout, it
crashes when it receives a SIGWINCH signal.
This can be reproduced as follows:
$ gdb/gdb -nx -batch -ex 'run' --args sleep 60 </dev/null 2>&1 | cat
# from another terminal:
$ kill -WINCH %(pidof gdb)
When doing so, the process crashes in a call to rl_resize_terminal:
void
rl_resize_terminal (void)
{
_rl_get_screen_size (fileno (rl_instream), 1);
...
}
The problem is that at this point rl_instream has the value NULL.
The rl_instream variable is supposed to be initialized during a call to
readline_initialize_everything, which in a normal startup sequence is
called under this call chain:
tui_interp::init
tui_ensure_readline_initialized
rl_initialize
readline_initialize_everything
In tui_interp::init, we have the following sequence:
tui_initialize_io ();
tui_initialize_win (); // <- Installs SIGWINCH
if (gdb_stdout->isatty ())
tui_ensure_readline_initialized (); // <- Initializes rl_instream
This function unconditionally installs the SIGWINCH signal handler (this
is done by tui_initialize_win), and then if gdb_stdout is a TTY it
initializes readline. Therefore, if stdout is not a TTY, SIGWINCH is
installed but readline is not initialized. In such situation
rl_instream stays NULL, and when GDB receives a SIGWINCH it calls its
handler and in fine tries to access rl_instream leading to the crash.
This patch proposes to fix this issue by installing the SIGWINCH signal
handler only if GDB is connected to a TTY. Given that this
initialization it the only task of tui_initialize_win, this patch moves
tui_initialize_win just after the call to
tui_ensure_readline_initialized.
Tested on x86_64-linux.
Co-authored-by: Pedro Alves <pedro@palves.net>
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=26056
Change-Id: I6458acef7b0d9beda2a10715d0345f02361076d9
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