From: Wolfgang Bangerth <bangerth@colostate.edu>
Date: Thu, 1 Nov 2018 14:22:40 +0000 (-0600)
Subject: Fix (Dynamic)?SparsityPattern::begin() for empty sparsity patterns.
X-Git-Tag: v9.1.0-rc1~583^2~3
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e4b5322c8fb33e007001b3d151d5ac0f7f0c8002;p=dealii.git

Fix (Dynamic)?SparsityPattern::begin() for empty sparsity patterns.
---

diff --git a/include/deal.II/lac/dynamic_sparsity_pattern.h b/include/deal.II/lac/dynamic_sparsity_pattern.h
index 4e21e2a9e4..d05dac7efa 100644
--- a/include/deal.II/lac/dynamic_sparsity_pattern.h
+++ b/include/deal.II/lac/dynamic_sparsity_pattern.h
@@ -1037,7 +1037,10 @@ DynamicSparsityPattern::column_number(const size_type row,
 inline DynamicSparsityPattern::iterator
 DynamicSparsityPattern::begin() const
 {
-  return begin(0);
+  if (n_rows() > 0)
+    return begin(0);
+  else
+    return end();
 }
 
 
diff --git a/include/deal.II/lac/sparsity_pattern.h b/include/deal.II/lac/sparsity_pattern.h
index 3caaa9d4a7..12c729bc7c 100644
--- a/include/deal.II/lac/sparsity_pattern.h
+++ b/include/deal.II/lac/sparsity_pattern.h
@@ -1254,7 +1254,10 @@ namespace SparsityPatternIterators
 inline SparsityPattern::iterator
 SparsityPattern::begin() const
 {
-  return iterator(this, rowstart[0]);
+  if (n_rows() > 0)
+    return iterator(this, rowstart[0]);
+  else
+    return end();
 }
 
 
@@ -1262,7 +1265,10 @@ SparsityPattern::begin() const
 inline SparsityPattern::iterator
 SparsityPattern::end() const
 {
-  return iterator(this, rowstart[rows]);
+  if (n_rows() > 0)
+    return iterator(this, rowstart[rows]);
+  else
+    return iterator(nullptr, 0);
 }