From bff1674c746edc0b71b022a8d48f739d76b89641 Mon Sep 17 00:00:00 2001
From: Luke Bratch <luke@bratch.co.uk>
Date: Sat, 18 May 2019 19:03:48 +0100
Subject: Add underflow safety check in appendcrlf().

---
 functions.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/functions.c b/functions.c
index ffd94f1..bc4680d 100644
--- a/functions.c
+++ b/functions.c
@@ -78,8 +78,11 @@ int getstdin(char *prompt, char *buff, size_t sz) {
 // Append CR-LF to the end of a string (after cleaning up any existing trailing CR or LF)
 void appendcrlf(char *string) {
   // Make sure it doesn't already end with CR or LF
-  while (string[strlen(string) - 1] == '\r' || string[strlen(string) - 1] == '\n') {
-    string[strlen(string) - 1] = '\0';
+  // (But only if string is at least two characters long already)
+  if (strlen(string) >= 2) {
+    while (string[strlen(string) - 1] == '\r' || string[strlen(string) - 1] == '\n') {
+      string[strlen(string) - 1] = '\0';
+    }
   }
 
   int startlen = strlen(string);
-- 
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