From dce590c29dbefea253f4034c4bde3508f205364e Mon Sep 17 00:00:00 2001
From: Yonatan Goldschmidt <yon.goldschmidt@gmail.com>
Date: Tue, 17 Dec 2019 22:40:40 +0200
Subject: [PATCH] lib/mp-readline: Add an assert() to catch buffer overflows.

During readline development, this function may receive bad `pos` values.
It's easier to understand the assert() failing error than to have a "stack
smashing detected" message.
---
 lib/mp-readline/readline.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/mp-readline/readline.c b/lib/mp-readline/readline.c
index 9d254d8cfe..1500873f69 100644
--- a/lib/mp-readline/readline.c
+++ b/lib/mp-readline/readline.c
@@ -74,6 +74,7 @@ STATIC void mp_hal_move_cursor_back(uint pos) {
         // snprintf needs space for the terminating null character
         int n = snprintf(&vt100_command[0], sizeof(vt100_command), "\x1b[%u", pos);
         if (n > 0) {
+            assert((unsigned)n < sizeof(vt100_command));
             vt100_command[n] = 'D'; // replace null char
             mp_hal_stdout_tx_strn(vt100_command, n + 1);
         }