diff --git a/src/ccstruct/polyblk.cpp b/src/ccstruct/polyblk.cpp
index 67021c0c..9d152c6a 100644
--- a/src/ccstruct/polyblk.cpp
+++ b/src/ccstruct/polyblk.cpp
@@ -1,8 +1,6 @@
 /**********************************************************************
  * File:        polyblk.cpp  (Formerly poly_block.c)
  * Description: Polygonal blocks
- * Author:          Sheelagh Lloyd?
- * Created:
  *
  * (C) Copyright 1993, Hewlett-Packard Ltd.
  ** Licensed under the Apache License, Version 2.0 (the "License");
@@ -45,14 +43,14 @@ POLY_BLOCK::POLY_BLOCK(ICOORDELT_LIST *points, PolyBlockType t) {
 }
 
 // Initialize from box coordinates.
-POLY_BLOCK::POLY_BLOCK(const TBOX& box, PolyBlockType t) {
+POLY_BLOCK::POLY_BLOCK(const TBOX& tbox, PolyBlockType t) {
   vertices.clear();
   ICOORDELT_IT v = &vertices;
   v.move_to_first();
-  v.add_to_end(new ICOORDELT(box.left(), box.top()));
-  v.add_to_end(new ICOORDELT(box.left(), box.bottom()));
-  v.add_to_end(new ICOORDELT(box.right(), box.bottom()));
-  v.add_to_end(new ICOORDELT(box.right(), box.top()));
+  v.add_to_end(new ICOORDELT(tbox.left(), tbox.top()));
+  v.add_to_end(new ICOORDELT(tbox.left(), tbox.bottom()));
+  v.add_to_end(new ICOORDELT(tbox.right(), tbox.bottom()));
+  v.add_to_end(new ICOORDELT(tbox.right(), tbox.top()));
   compute_bb();
   type = t;
 }
diff --git a/src/ccstruct/polyblk.h b/src/ccstruct/polyblk.h
index 08703722..62baa222 100644
--- a/src/ccstruct/polyblk.h
+++ b/src/ccstruct/polyblk.h
@@ -28,7 +28,7 @@ class DLLSYM POLY_BLOCK {
  public:
   POLY_BLOCK() = default;
   // Initialize from box coordinates.
-  POLY_BLOCK(const TBOX& box, PolyBlockType type);
+  POLY_BLOCK(const TBOX& tbox, PolyBlockType type);
   POLY_BLOCK(ICOORDELT_LIST *points, PolyBlockType type);
   ~POLY_BLOCK () = default;
 
diff --git a/src/lstm/lstmrecognizer.cpp b/src/lstm/lstmrecognizer.cpp
index c3ae7a40..060cf261 100644
--- a/src/lstm/lstmrecognizer.cpp
+++ b/src/lstm/lstmrecognizer.cpp
@@ -408,6 +408,7 @@ void LSTMRecognizer::DebugActivationRange(const NetworkIO& outputs,
 // Helper returns true if the null_char is the winner at t, and it beats the
 // null_threshold, or the next choice is space, in which case we will use the
 // null anyway.
+#if 0 // TODO: unused, remove if still unused after 2020.
 static bool NullIsBest(const NetworkIO& output, float null_thr,
                        int null_char, int t) {
   if (output.f(t)[null_char] >= null_thr) return true;
@@ -415,6 +416,7 @@ static bool NullIsBest(const NetworkIO& output, float null_thr,
     return false;
   return output.f(t)[null_char] > output.f(t)[UNICHAR_SPACE];
 }
+#endif
 
 // Converts the network output to a sequence of labels. Outputs labels, scores
 // and start xcoords of each char, and each null_char_, with an additional
diff --git a/src/lstm/network.cpp b/src/lstm/network.cpp
index db0c7078..3dc28229 100644
--- a/src/lstm/network.cpp
+++ b/src/lstm/network.cpp
@@ -244,7 +244,6 @@ Network* Network::CreateFromFile(TFile* fp) {
       network = new TFNetwork(stub.name_);
 #else
       tprintf("TensorFlow not compiled in! -DINCLUDE_TENSORFLOW\n");
-      return nullptr;
 #endif
       break;
     // All variants of FullyConnected.
@@ -259,15 +258,16 @@ Network* Network::CreateFromFile(TFile* fp) {
       network = new FullyConnected(stub.name_, stub.ni_, stub.no_, stub.type_);
       break;
     default:
-      return nullptr;
   }
-  network->training_ = stub.training_;
-  network->needs_to_backprop_ = stub.needs_to_backprop_;
-  network->network_flags_ = stub.network_flags_;
-  network->num_weights_ = stub.num_weights_;
-  if (!network->DeSerialize(fp)) {
-    delete network;
-    return nullptr;
+  if (network) {
+    network->training_ = stub.training_;
+    network->needs_to_backprop_ = stub.needs_to_backprop_;
+    network->network_flags_ = stub.network_flags_;
+    network->num_weights_ = stub.num_weights_;
+    if (!network->DeSerialize(fp)) {
+      delete network;
+      network =‌ nullptr;
+    }
   }
   return network;
 }
diff --git a/src/lstm/networkio.cpp b/src/lstm/networkio.cpp
index 405977e9..88f3f409 100644
--- a/src/lstm/networkio.cpp
+++ b/src/lstm/networkio.cpp
@@ -50,10 +50,9 @@ void NetworkIO::Resize2d(bool int_mode, int width, int num_features) {
 // Resizes to a specific stride_map.
 void NetworkIO::ResizeToMap(bool int_mode, const StrideMap& stride_map,
                             int num_features) {
-  // If this assert fails, it most likely got here through an uninitialized
-  // scratch element, ie call NetworkScratch::IO::Resizexxx() not
-  // NetworkIO::Resizexxx()!!
-  ASSERT_HOST(this != nullptr);
+  // If this method crashes with this == nullptr,
+  // it most likely got here through an uninitialized scratch element,
+  // ie call NetworkScratch::IO::Resizexxx() not NetworkIO::Resizexxx()!!
   stride_map_ = stride_map;
   int_mode_ = int_mode;
   if (int_mode_) {