From d29419bcd69432aded1df73cb74853db86daf20d Mon Sep 17 00:00:00 2001
From: Maxime Coste <frrrwww@gmail.com>
Date: Tue, 28 Oct 2014 21:55:08 +0000
Subject: [PATCH] Fix invalid memory access when applying modifications on an
 empty buffer

That can happen when undoing/redoing accross a buffer reload
boundary.
---
 src/buffer.cc     | 4 +++-
 src/buffer.inl.hh | 8 ++++----
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/src/buffer.cc b/src/buffer.cc
index 81804c79..0b0dca1e 100644
--- a/src/buffer.cc
+++ b/src/buffer.cc
@@ -351,7 +351,9 @@ void Buffer::apply_modification(const Modification& modification)
 
     kak_assert(is_valid(coord));
     // in modifications, end coords should be {line_count(), 0}
-    kak_assert(coord != ByteCoord(line_count()-1, m_lines.back().length()));
+    kak_assert((m_lines.empty() and coord == ByteCoord{0,0} ) or
+               coord != ByteCoord(line_count()-1, m_lines.back().length()));
+
     switch (modification.type)
     {
     case Modification::Insert:
diff --git a/src/buffer.inl.hh b/src/buffer.inl.hh
index 0e82b7a9..7b09f1a4 100644
--- a/src/buffer.inl.hh
+++ b/src/buffer.inl.hh
@@ -68,7 +68,7 @@ inline bool Buffer::is_valid(ByteCoord c) const
 
 inline bool Buffer::is_end(ByteCoord c) const
 {
-    return c >= ByteCoord{line_count() - 1, m_lines.back().length()};
+    return c >= end_coord();
 }
 
 inline BufferIterator Buffer::begin() const
@@ -78,9 +78,7 @@ inline BufferIterator Buffer::begin() const
 
 inline BufferIterator Buffer::end() const
 {
-    if (m_lines.empty())
-        return BufferIterator(*this, { 0_line, 0 });
-    return BufferIterator(*this, { line_count() - 1, m_lines.back().length() });
+    return BufferIterator{*this, end_coord()};
 }
 
 [[gnu::always_inline]]
@@ -107,6 +105,8 @@ inline ByteCoord Buffer::back_coord() const
 
 inline ByteCoord Buffer::end_coord() const
 {
+    if (m_lines.empty())
+        return { 0_line, 0 };
     return { line_count() - 1, m_lines.back().length() };
 }