From 2d96ddcf623f6977d6aad3c7ce1cedf801800c47 Mon Sep 17 00:00:00 2001
From: Axel Kohlmeyer <akohlmey@gmail.com>
Date: Fri, 24 Jun 2016 18:59:58 -0400
Subject: [PATCH] teach read_data to handle empty XXX Coeffs sections and
 write_data to not generate them.

---
 src/read_data.cpp  | 8 ++++++++
 src/write_data.cpp | 8 ++++----
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/src/read_data.cpp b/src/read_data.cpp
index 39afcfbcf8..ed9544ade7 100644
--- a/src/read_data.cpp
+++ b/src/read_data.cpp
@@ -1701,6 +1701,8 @@ void ReadData::pairIJcoeffs()
 
 void ReadData::bondcoeffs()
 {
+  if (!nbondtypes) return;
+
   char *next;
   char *buf = new char[nbondtypes*MAXLINE];
 
@@ -1723,6 +1725,8 @@ void ReadData::bondcoeffs()
 
 void ReadData::anglecoeffs(int which)
 {
+  if (!nangletypes) return;
+
   char *next;
   char *buf = new char[nangletypes*MAXLINE];
 
@@ -1747,6 +1751,8 @@ void ReadData::anglecoeffs(int which)
 
 void ReadData::dihedralcoeffs(int which)
 {
+  if (!ndihedraltypes) return;
+
   char *next;
   char *buf = new char[ndihedraltypes*MAXLINE];
 
@@ -1774,6 +1780,8 @@ void ReadData::dihedralcoeffs(int which)
 
 void ReadData::impropercoeffs(int which)
 {
+  if (!nimpropertypes) return;
+
   char *next;
   char *buf = new char[nimpropertypes*MAXLINE];
 
diff --git a/src/write_data.cpp b/src/write_data.cpp
index 5a67c1081e..d8b951dd8c 100644
--- a/src/write_data.cpp
+++ b/src/write_data.cpp
@@ -286,19 +286,19 @@ void WriteData::force_fields()
       force->pair->write_data_all(fp);
     }
   }
-  if (force->bond && force->bond->writedata) {
+  if (force->bond && force->bond->writedata && atom->nbondtypes) {
     fprintf(fp,"\nBond Coeffs # %s\n\n", force->bond_style);
     force->bond->write_data(fp);
   }
-  if (force->angle && force->angle->writedata) {
+  if (force->angle && force->angle->writedata && atom->nangletypes) {
     fprintf(fp,"\nAngle Coeffs # %s\n\n", force->angle_style);
     force->angle->write_data(fp);
   }
-  if (force->dihedral && force->dihedral->writedata) {
+  if (force->dihedral && force->dihedral->writedata && atom->ndihedraltypes) {
     fprintf(fp,"\nDihedral Coeffs # %s\n\n", force->dihedral_style);
     force->dihedral->write_data(fp);
   }
-  if (force->improper && force->improper->writedata) {
+  if (force->improper && force->improper->writedata && atom->nimpropertypes) {
     fprintf(fp,"\nImproper Coeffs # %s\n\n", force->improper_style);
     force->improper->write_data(fp);
   }