From 749c7adb1315e5d84161353e99e2dde20a8de2a6 Mon Sep 17 00:00:00 2001
From: Prateek Machiraju <prateek.machiraju@gmail.com>
Date: Thu, 31 Dec 2020 23:35:17 -0500
Subject: [PATCH] [command] Fix use-after-free in CommandScheduler (#3024)

---
 .../src/main/native/cpp/frc2/command/CommandScheduler.cpp   | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/wpilibNewCommands/src/main/native/cpp/frc2/command/CommandScheduler.cpp b/wpilibNewCommands/src/main/native/cpp/frc2/command/CommandScheduler.cpp
index f13c53fbe9..3acd9b5fdd 100644
--- a/wpilibNewCommands/src/main/native/cpp/frc2/command/CommandScheduler.cpp
+++ b/wpilibNewCommands/src/main/native/cpp/frc2/command/CommandScheduler.cpp
@@ -84,6 +84,8 @@ CommandScheduler::~CommandScheduler() {
   auto scheduler = frc::LiveWindow::GetInstance();
   scheduler->enabled = nullptr;
   scheduler->disabled = nullptr;
+
+  std::unique_ptr<Impl>().swap(m_impl);
 }
 
 CommandScheduler& CommandScheduler::GetInstance() {
@@ -312,6 +314,10 @@ Command* CommandScheduler::GetDefaultCommand(const Subsystem* subsystem) const {
 }
 
 void CommandScheduler::Cancel(Command* command) {
+  if (!m_impl) {
+    return;
+  }
+
   if (m_impl->inRunLoop) {
     m_impl->toCancel.emplace_back(command);
     return;