ash: fix bad interaction of "stty -echo" + ASK_TERMINAL

function                                             old     new   delta
read_line_input                                     4820    4886     +66
put_prompt                                           108      47     -61
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 1/1 up/down: 66/-61)              Total: 5 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

diff --git a/libbb/lineedit.c b/libbb/lineedit.c
index a9972576e3aa84efbd667a2b9a2de66934eeaef3..7bb3f2e356489bfd083e45efd20f3a7f7199c657 100644 (file)
--- a/libbb/lineedit.c
+++ b/libbb/lineedit.c
@@ -372,55 +372,14 @@ static void input_backward(unsigned num)
 
 static void put_prompt(void)
 {
+       unsigned w;
+
        out1str(cmdedit_prompt);
        fflush_all();
-#if ENABLE_FEATURE_EDITING_ASK_TERMINAL
-       {
-               /* Ask terminal where is the cursor now.
-                * lineedit_read_key handles response and corrects
-                * our idea of current cursor position.
-                * Testcase: run "echo -n long_line_long_line_long_line",
-                * then type in a long, wrapping command and try to
-                * delete it using backspace key.
-                * Note: we print it _after_ prompt, because
-                * prompt may contain CR. Example: PS1='\[\r\n\]\w '
-                */
-               /* Problem: if there is buffered input on stdin,
-                * the response will be delivered later,
-                * possibly to an unsuspecting application.
-                * Testcase: "sleep 1; busybox ash" + press and hold [Enter].
-                * Result:
-                * ~/srcdevel/bbox/fix/busybox.t4 #
-                * ~/srcdevel/bbox/fix/busybox.t4 #
-                * ^[[59;34~/srcdevel/bbox/fix/busybox.t4 #  <-- garbage
-                * ~/srcdevel/bbox/fix/busybox.t4 #
-                *
-                * Checking for input with poll only makes the race narrower,
-                * I still can trigger it. Strace:
-                *
-                * write(1, "~/srcdevel/bbox/fix/busybox.t4 # ", 33) = 33
-                * poll([{fd=0, events=POLLIN}], 1, 0) = 0 (Timeout)  <-- no input exists
-                * write(1, "\33[6n", 4) = 4  <-- send the ESC sequence, quick!
-                * poll([{fd=0, events=POLLIN}], 1, 4294967295) = 1 ([{fd=0, revents=POLLIN}])
-                * read(0, "\n", 1)      = 1  <-- oh crap, user's input got in first
-                */
-               struct pollfd pfd;
-
-               pfd.fd = STDIN_FILENO;
-               pfd.events = POLLIN;
-               if (safe_poll(&pfd, 1, 0) == 0) {
-                       S.sent_ESC_br6n = 1;
-                       out1str("\033" "[6n");
-                       fflush_all(); /* make terminal see it ASAP! */
-               }
-       }
-#endif
        cursor = 0;
-       {
-               unsigned w = cmdedit_termw; /* volatile var */
-               cmdedit_y = cmdedit_prmt_len / w; /* new quasireal y */
-               cmdedit_x = cmdedit_prmt_len % w;
-       }
+       w = cmdedit_termw; /* read volatile var once */
+       cmdedit_y = cmdedit_prmt_len / w; /* new quasireal y */
+       cmdedit_x = cmdedit_prmt_len % w;
 }
 
 /* draw prompt, editor line, and clear tail */
@@ -1503,6 +1462,51 @@ static void ctrl_right(void)
  * read_line_input and its helpers
  */
 
+#if ENABLE_FEATURE_EDITING_ASK_TERMINAL
+static void ask_terminal(void)
+{
+       /* Ask terminal where is the cursor now.
+        * lineedit_read_key handles response and corrects
+        * our idea of current cursor position.
+        * Testcase: run "echo -n long_line_long_line_long_line",
+        * then type in a long, wrapping command and try to
+        * delete it using backspace key.
+        * Note: we print it _after_ prompt, because
+        * prompt may contain CR. Example: PS1='\[\r\n\]\w '
+        */
+       /* Problem: if there is buffered input on stdin,
+        * the response will be delivered later,
+        * possibly to an unsuspecting application.
+        * Testcase: "sleep 1; busybox ash" + press and hold [Enter].
+        * Result:
+        * ~/srcdevel/bbox/fix/busybox.t4 #
+        * ~/srcdevel/bbox/fix/busybox.t4 #
+        * ^[[59;34~/srcdevel/bbox/fix/busybox.t4 #  <-- garbage
+        * ~/srcdevel/bbox/fix/busybox.t4 #
+        *
+        * Checking for input with poll only makes the race narrower,
+        * I still can trigger it. Strace:
+        *
+        * write(1, "~/srcdevel/bbox/fix/busybox.t4 # ", 33) = 33
+        * poll([{fd=0, events=POLLIN}], 1, 0) = 0 (Timeout)  <-- no input exists
+        * write(1, "\33[6n", 4) = 4  <-- send the ESC sequence, quick!
+        * poll([{fd=0, events=POLLIN}], 1, 4294967295) = 1 ([{fd=0, revents=POLLIN}])
+        * read(0, "\n", 1)      = 1  <-- oh crap, user's input got in first
+        */
+       struct pollfd pfd;
+
+       pfd.fd = STDIN_FILENO;
+       pfd.events = POLLIN;
+       if (safe_poll(&pfd, 1, 0) == 0) {
+               S.sent_ESC_br6n = 1;
+               out1str("\033" "[6n");
+               fflush_all(); /* make terminal see it ASAP! */
+       }
+}
+#else
+#define ask_terminal() ((void)0)
+#endif
+
 #if !ENABLE_FEATURE_EDITING_FANCY_PROMPT
 static void parse_and_put_prompt(const char *prmt_ptr)
 {
@@ -1822,8 +1826,9 @@ int FAST_FUNC read_line_input(const char *prompt, char *command, int maxsize, li
        bb_error_msg("cur_history:%d cnt_history:%d", state->cur_history, state->cnt_history);
 #endif
 
-       /* Print out the command prompt */
+       /* Print out the command prompt, optionally ask where cursor is */
        parse_and_put_prompt(prompt);
+       ask_terminal();
 
        read_key_buffer[0] = 0;
        while (1) {