vi: explain why reading 4 chars is unsafe

1 files changed, 5 insertions, 3 deletions

diff --git a/editors/vi.c b/editors/vi.c
index acbede359..8944f770a 100644
--- a/editors/vi.c
+++ b/editors/vi.c
@@ -2243,9 +2243,11 @@ static char readit(void)	// read (maybe cursor) key from stdin
 
         n = chars_to_parse;
         if (n == 0) {
-                // If no data, block waiting for input
-                // (can't read more than minimal ESC sequence -
-                // see "n = 0" below).
+                // If no data, block waiting for input.
+                // Can't read more than minimal ESC sequence size -
+                // see "n = 0" below. Example of mishandled
+                // sequence if we read 4 chars here: "ESC O A ESC O A".
+                // We'll read "ESC O A ESC" and lose second ESC!
                 n = safe_read(0, readbuffer, 3);
                 if (n <= 0) {
  error: