From ffdea773fff2fa13ea576e76213d92d553bac26a Mon Sep 17 00:00:00 2001
From: Oz Amram <oamram1@jhu.edu>
Date: Tue, 14 Sep 2021 14:39:26 -0500
Subject: [PATCH 1/3] copy_to_buffer return right away if range empty

---
 .../SiPixelClusterizer/plugins/PixelThresholdClusterizer.cc  | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/RecoLocalTracker/SiPixelClusterizer/plugins/PixelThresholdClusterizer.cc b/RecoLocalTracker/SiPixelClusterizer/plugins/PixelThresholdClusterizer.cc
index 26b9a64ea3a52..433eefe720030 100644
--- a/RecoLocalTracker/SiPixelClusterizer/plugins/PixelThresholdClusterizer.cc
+++ b/RecoLocalTracker/SiPixelClusterizer/plugins/PixelThresholdClusterizer.cc
@@ -222,6 +222,11 @@ void PixelThresholdClusterizer::copy_to_buffer(DigiIterator begin, DigiIterator
     // std::cout << (doMissCalibrate ? "VI from db" : "VI linear") << std::endl;
   }
 #endif
+
+  //avoid undefined behavior
+  if (end <= begin)
+    return;
+
   int electron[end - begin];  // pixel charge in electrons
   memset(electron, 0, (end - begin) * sizeof(int));
 

From f8f2afc821bfba3dc0d2f5cee4ff7845beec7e7a Mon Sep 17 00:00:00 2001
From: Oz Amram <oamram1@jhu.edu>
Date: Mon, 20 Sep 2021 10:10:56 -0500
Subject: [PATCH 2/3] Check range before calling copy_to_buffer, add LogWarning

---
 .../plugins/PixelThresholdClusterizer.cc                 | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/RecoLocalTracker/SiPixelClusterizer/plugins/PixelThresholdClusterizer.cc b/RecoLocalTracker/SiPixelClusterizer/plugins/PixelThresholdClusterizer.cc
index 433eefe720030..e1ba455a249ac 100644
--- a/RecoLocalTracker/SiPixelClusterizer/plugins/PixelThresholdClusterizer.cc
+++ b/RecoLocalTracker/SiPixelClusterizer/plugins/PixelThresholdClusterizer.cc
@@ -148,7 +148,8 @@ void PixelThresholdClusterizer::clusterizeDetUnitT(const T& input,
 
   //  Copy PixelDigis to the buffer array; select the seed pixels
   //  on the way, and store them in theSeeds.
-  copy_to_buffer(begin, end);
+  if (end > begin)
+    copy_to_buffer(begin, end);
 
   assert(output.empty());
   //  Loop over all seeds.  TO DO: wouldn't using iterators be faster?
@@ -223,9 +224,11 @@ void PixelThresholdClusterizer::copy_to_buffer(DigiIterator begin, DigiIterator
   }
 #endif
 
-  //avoid undefined behavior
-  if (end <= begin)
+  //If called with empty / invalid DetSet, warn the user
+  if (end <= begin) {
+    edm::LogWarning("PixelThresholdClusterizer") << " copy_to_buffer called with empty or invalid range" << std::endl;
     return;
+  }
 
   int electron[end - begin];  // pixel charge in electrons
   memset(electron, 0, (end - begin) * sizeof(int));

From 866cfe791c3256b9f6354523dd9ff43620c631fa Mon Sep 17 00:00:00 2001
From: Malik Shahzad Muzaffar <shahzad.malik.muzaffar@cern.ch>
Date: Tue, 28 Sep 2021 08:08:37 +0200
Subject: [PATCH 3/3] force dummy commit to change the commit as bot has
 reached max commit status for this

---
 .../SiPixelClusterizer/plugins/PixelThresholdClusterizer.cc     | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/RecoLocalTracker/SiPixelClusterizer/plugins/PixelThresholdClusterizer.cc b/RecoLocalTracker/SiPixelClusterizer/plugins/PixelThresholdClusterizer.cc
index e1ba455a249ac..5aac76529ab0a 100644
--- a/RecoLocalTracker/SiPixelClusterizer/plugins/PixelThresholdClusterizer.cc
+++ b/RecoLocalTracker/SiPixelClusterizer/plugins/PixelThresholdClusterizer.cc
@@ -224,7 +224,7 @@ void PixelThresholdClusterizer::copy_to_buffer(DigiIterator begin, DigiIterator
   }
 #endif
 
-  //If called with empty / invalid DetSet, warn the user
+  //If called with empty/invalid DetSet, warn the user
   if (end <= begin) {
     edm::LogWarning("PixelThresholdClusterizer") << " copy_to_buffer called with empty or invalid range" << std::endl;
     return;