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>

1 files changed, 52 insertions, 47 deletions

diff --git a/libbb/lineedit.c b/libbb/lineedit.c
index a9972576e..7bb3f2e35 100644
--- 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) {