From: Wolfgang Bangerth <bangerth@colostate.edu>
Date: Wed, 21 Mar 2018 20:09:12 +0000 (-0600)
Subject: Ensure we get no segmentation faults for empty matrices.
X-Git-Tag: v9.0.0-rc1~287^2~1
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=586c3b03f8664ad2ef69167e95cd0cba8c54640b;p=dealii.git

Ensure we get no segmentation faults for empty matrices.
---

diff --git a/source/lac/sparsity_pattern.cc b/source/lac/sparsity_pattern.cc
index c71504eee0..5c0a2f04b9 100644
--- a/source/lac/sparsity_pattern.cc
+++ b/source/lac/sparsity_pattern.cc
@@ -572,8 +572,12 @@ void SparsityPattern::copy_from (const FullMatrix<number> &matrix)
   // but there are cases where it matters -- so we may as well be
   // gentler and hand over a whole row of entries at a time
   std::vector<size_type> column_indices;
-  column_indices.reserve (*std::max_element (entries_per_row.begin(),
-                                             entries_per_row.end()));
+  column_indices.reserve (entries_per_row.size() > 0
+                          ?
+                          *std::max_element (entries_per_row.begin(),
+                                             entries_per_row.end())
+                          :
+                          0);
   for (size_type row=0; row<matrix.m(); ++row)
     {
       column_indices.resize(entries_per_row[row]);