From 1e0ec182c166da505ad1404fcbf80240a3797ae4 Mon Sep 17 00:00:00 2001
From: Maxime Coste <frrrwww@gmail.com>
Date: Mon, 26 Sep 2016 23:24:04 +0100
Subject: [PATCH] Assert substr from parameter is within the string

Should catch #756 earlier if it happens again.
---
 src/string.hh | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/string.hh b/src/string.hh
index 74fbb51a..be140888 100644
--- a/src/string.hh
+++ b/src/string.hh
@@ -231,7 +231,9 @@ inline StringView StringOps<Type, CharType>::substr(ByteCount from, ByteCount le
 {
     if (length < 0)
         length = INT_MAX;
-    return StringView{ type().data() + (int)from, std::min(type().length() - from, length) };
+    const auto str_len = type().length();
+    kak_assert(from >= 0 and from <= str_len);
+    return StringView{ type().data() + (int)from, std::min(str_len - from, length) };
 }
 
 template<typename Type, typename CharType>