From 84eda397bcf3ebea00383e4a6a864af59723dafd Mon Sep 17 00:00:00 2001 From: Pedro Alves Date: Wed, 29 Oct 2014 14:23:57 +0000 Subject: [PATCH] PR tui/16138, PR tui/17519, and misc failures to initialize the terminal PR tui/16138 is about failure to initialize curses resulting in GDB exiting instead of throwing an error. E.g.: $ TERM=foo gdb (gdb) layout asm Error opening terminal: foo. $ The problem is that we're calling initscr to initialize the screen. As mentioned in http://pubs.opengroup.org/onlinepubs/7908799/xcurses/initscr.html: If errors occur, initscr() writes an appropriate error message to standard error and exits. ^^^^^ Instead, we should use newterm: "A program that needs an indication of error conditions, so it can continue to run in a line-oriented mode if the terminal cannot support a screen-oriented program, would also use this function." After the patch: $ TERM=foo gdb -q -nx (gdb) layout asm Cannot enable the TUI: error opening terminal [TERM=foo] (gdb) And then PR tui/17519 is about GDB not validating whether the terminal has the necessary capabilities when enabling the TUI. If one tries to enable the TUI with TERM=dumb (and e.g., from a shell within emacs), GDB ends up with a clear screen, the cursor is placed at the bottom/right corner of the screen, there's no prompt, typing shows no echo, and there's no indication of what's going on. c-x,a gets you out of the TUI, but it's completely non-obvious. After the patch, we get: $ TERM=dumb gdb -q -nx (gdb) layout asm Cannot enable the TUI: terminal doesn't support cursor addressing [TERM=dumb] (gdb) While at it, I've moved all the tui_allowed_p validation to tui_enable, and expanded the error messages. Previously we'd get: $ gdb -q -nx -i=mi (gdb) layout asm &"layout asm\n" &"TUI mode not allowed\n" ^error,msg="TUI mode not allowed" and: $ gdb -q -nx -ex "layout asm" > foo TUI mode not allowed While now we get: $ gdb -q -nx -i=mi (gdb) layout asm &"layout asm\n" &"Cannot enable the TUI when the interpreter is 'mi'\n" ^error,msg="Cannot enable the TUI when the interpreter is 'mi'" (gdb) and: $ gdb -q -nx -ex "layout asm" > foo Cannot enable the TUI when output is not a terminal Tested on x86_64 Fedora 20. gdb/ 2014-10-29 Pedro Alves PR tui/16138 PR tui/17519 * tui/tui-interp.c (tui_is_toplevel): Delete global. (tui_allowed_p): Delete function. * tui/tui.c: Include "interps.h". (tui_enable): Don't use tui_allowed_p. Error out here with detailed error messages if the TUI is the top level interpreter, or if output is not a terminal. Use newterm instead of initscr, and error out if initializing the terminal fails. Also error out if the terminal doesn't support cursor addressing. * tui/tui.h (tui_allowed_p): Delete declaration. --- gdb/tui/tui-interp.c | 17 -------------- gdb/tui/tui.c | 53 ++++++++++++++++++++++++++++++++++++++++---- gdb/tui/tui.h | 4 ---- 3 files changed, 49 insertions(+), 25 deletions(-) diff --git a/gdb/tui/tui-interp.c b/gdb/tui/tui-interp.c index 24cb5a3941..b377db25a2 100644 --- a/gdb/tui/tui-interp.c +++ b/gdb/tui/tui-interp.c @@ -51,9 +51,6 @@ tui_exit (void) tui_disable (); } -/* True if TUI is the top-level interpreter. */ -static int tui_is_toplevel = 0; - /* Observers for several run control events. If the interpreter is quiet (i.e., another interpreter is being run with interpreter-exec), print nothing. */ @@ -126,8 +123,6 @@ tui_on_command_error (void) static void * tui_init (struct interp *self, int top_level) { - tui_is_toplevel = top_level; - /* Install exit handler to leave the screen in a good shape. */ atexit (tui_exit); @@ -150,18 +145,6 @@ tui_init (struct interp *self, int top_level) return NULL; } -/* True if enabling the TUI is allowed. Example, if the top level - interpreter is MI, enabling curses will certainly lose. */ - -int -tui_allowed_p (void) -{ - /* Only if TUI is the top level interpreter. Also don't try to - setup curses (and print funny control characters) if we're not - outputting to a terminal. */ - return tui_is_toplevel && ui_file_isatty (gdb_stdout); -} - static int tui_resume (void *data) { diff --git a/gdb/tui/tui.c b/gdb/tui/tui.c index a02c85563a..ca66ccd0f4 100644 --- a/gdb/tui/tui.c +++ b/gdb/tui/tui.c @@ -48,6 +48,7 @@ #include #include "gdb_curses.h" +#include "interps.h" /* This redefines CTRL if it is not already defined, so it must come after terminal state releated include files like and @@ -361,6 +362,20 @@ tui_initialize_readline (void) rl_bind_key_in_map ('s', tui_rl_next_keymap, tui_ctlx_keymap); } +/* Return the TERM variable from the environment, or "" + if not set. */ + +static const char * +gdb_getenv_term (void) +{ + const char *term; + + term = getenv ("TERM"); + if (term != NULL) + return term; + return ""; +} + /* Enter in the tui mode (curses). When in normal mode, it installs the tui hooks in gdb, redirects the gdb output, configures the readline to work in tui mode. @@ -368,8 +383,7 @@ tui_initialize_readline (void) void tui_enable (void) { - if (!tui_allowed_p ()) - error (_("TUI mode not allowed")); + struct interp *interp; if (tui_active) return; @@ -380,9 +394,40 @@ tui_enable (void) if (tui_finish_init) { WINDOW *w; + SCREEN *s; + const char *cap; + const char *interp; + + /* If the top level interpreter is not the console/tui (e.g., + MI), enabling curses will certainly lose. */ + interp = interp_name (top_level_interpreter ()); + if (strcmp (interp, INTERP_TUI) != 0) + error (_("Cannot enable the TUI when the interpreter is '%s'"), interp); + + /* Don't try to setup curses (and print funny control + characters) if we're not outputting to a terminal. */ + if (!ui_file_isatty (gdb_stdout)) + error (_("Cannot enable the TUI when output is not a terminal")); + + s = newterm (NULL, NULL, NULL); + if (s == NULL) + { + error (_("Cannot enable the TUI: error opening terminal [TERM=%s]"), + gdb_getenv_term ()); + } + w = stdscr; + + /* Check required terminal capabilities. */ + cap = tigetstr ("cup"); + if (cap == NULL || cap == (char *) -1 || *cap == '\0') + { + endwin (); + delscreen (s); + error (_("Cannot enable the TUI: " + "terminal doesn't support cursor addressing [TERM=%s]"), + gdb_getenv_term ()); + } - w = initscr (); - cbreak (); noecho (); /* timeout (1); */ diff --git a/gdb/tui/tui.h b/gdb/tui/tui.h index 9afadb20c1..b1dddc0c3b 100644 --- a/gdb/tui/tui.h +++ b/gdb/tui/tui.h @@ -64,10 +64,6 @@ extern int tui_get_command_dimension (unsigned int *width, key shortcut. */ extern void tui_initialize_readline (void); -/* True if enabling the TUI is allowed. Example, if the top level - interpreter is MI, enabling curses will certainly lose. */ -extern int tui_allowed_p (void); - /* Enter in the tui mode (curses). */ extern void tui_enable (void);