From a9a04e81b0c1e62e1554dfc89806955c98fcd7d8 Mon Sep 17 00:00:00 2001
From: Maxime Coste <mawww@kakoune.org>
Date: Mon, 18 Sep 2017 11:30:01 +0900
Subject: [PATCH] Regex: Ensure we only ever have a single thread on a given
 instruction

---
 src/regex_impl.cc | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/regex_impl.cc b/src/regex_impl.cc
index 6fc513d7..1378fcd2 100644
--- a/src/regex_impl.cc
+++ b/src/regex_impl.cc
@@ -311,10 +311,13 @@ struct ThreadedExecutor
                     return { StepResult::Consumed, inst };
                 case RegexProgram::Jump:
                     inst = m_program.begin() + *reinterpret_cast<const RegexProgram::Offset*>(inst);
+                    // if instruction is already going to be executed, drop this thread
+                    if (std::find(m_threads.begin(), m_threads.end(), inst) != m_threads.end())
+                        return { StepResult::Failed };
                     break;
                 case RegexProgram::Split:
                 {
-                    m_threads.push_back(m_program.begin() + *reinterpret_cast<const RegexProgram::Offset*>(inst));
+                    add_thread(*reinterpret_cast<const RegexProgram::Offset*>(inst));
                     inst += sizeof(RegexProgram::Offset);
                     break;
                 }
@@ -362,6 +365,13 @@ struct ThreadedExecutor
         return false;
     }
 
+    void add_thread(RegexProgram::Offset pos)
+    {
+        const char* inst = m_program.begin() + pos;
+        if (std::find(m_threads.begin(), m_threads.end(), inst) == m_threads.end())
+            m_threads.push_back(inst);
+    }
+
     bool is_line_start() const
     {
         return m_pos == m_subject.begin() or *(m_pos-1) == '\n';