From fc64369f9d8d3279f73b89fdd76df2fa1468ff72 Mon Sep 17 00:00:00 2001
From: Maxime Coste <mawww@kakoune.org>
Date: Fri, 4 Aug 2017 11:39:28 +0700
Subject: [PATCH] Purge history on buffer reload when NoUndo flag is on

We were preserving the history in that case, so on fifo buffers
(that set the NoUndo flag until the fifo is closed), we still had
the history from the "previous life" of the buffer, leading crashes
when trying to apply it.

Fixes #1518
---
 src/buffer.cc                                            | 9 ++++++---
 src/buffer.hh                                            | 4 ++--
 .../1518-wrong-undo-handling-with-fifo-buffers/cmd       | 1 +
 3 files changed, 9 insertions(+), 5 deletions(-)
 create mode 100644 test/regression/1518-wrong-undo-handling-with-fifo-buffers/cmd

diff --git a/src/buffer.cc b/src/buffer.cc
index b85d01ee..147e1bbf 100644
--- a/src/buffer.cc
+++ b/src/buffer.cc
@@ -242,10 +242,13 @@ void Buffer::reload(StringView data, timespec fs_timestamp)
 
     if (not record_undo)
     {
+        // Erase history about to be invalidated history
+        m_history_cursor = &m_history;
+        m_last_save_history_cursor = &m_history;
+        m_history = HistoryNode{m_next_history_id++, nullptr};
+
         m_changes.push_back({ Change::Erase, {0,0}, line_count() });
-
         static_cast<BufferLines&>(m_lines) = std::move(parsed_lines.lines);
-
         m_changes.push_back({ Change::Insert, {0,0}, line_count() });
     }
     else
@@ -340,7 +343,7 @@ bool Buffer::redo(size_t count) noexcept
 
     while (count-- != 0 and m_history_cursor->redo_child)
     {
-        m_history_cursor = m_history_cursor->redo_child.get();
+        m_history_cursor = m_history_cursor->redo_child;
 
         for (const Modification& modification : m_history_cursor->undo_group)
             apply_modification(modification);
diff --git a/src/buffer.hh b/src/buffer.hh
index ee03c0a0..7cf2db7b 100644
--- a/src/buffer.hh
+++ b/src/buffer.hh
@@ -252,14 +252,14 @@ private:
 
     using UndoGroup = Vector<Modification, MemoryDomain::BufferMeta>;
 
-    struct HistoryNode : SafeCountable, UseMemoryDomain<MemoryDomain::BufferMeta>
+   struct HistoryNode : SafeCountable, UseMemoryDomain<MemoryDomain::BufferMeta>
     {
         HistoryNode(size_t id, HistoryNode* parent);
 
         UndoGroup undo_group;
         Vector<std::unique_ptr<HistoryNode>, MemoryDomain::BufferMeta> childs;
         SafePtr<HistoryNode> parent;
-        SafePtr<HistoryNode> redo_child;
+        HistoryNode* redo_child = nullptr; // not a SafePtr to avoid lifetime issues between this and childs
         size_t id;
         TimePoint timepoint;
     };
diff --git a/test/regression/1518-wrong-undo-handling-with-fifo-buffers/cmd b/test/regression/1518-wrong-undo-handling-with-fifo-buffers/cmd
new file mode 100644
index 00000000..a8902d2d
--- /dev/null
+++ b/test/regression/1518-wrong-undo-handling-with-fifo-buffers/cmd
@@ -0,0 +1 @@
+<a-O>ifoo<c-u><esc>:edit -fifo /dev/null <c-r>%<ret>u