Don't store group if initial assignment failed

src/group.cpp

@@ -30,6 +30,7 @@
 #include "region.h"
 #include "tokenizer.h"
 #include "variable.h"
+#include "exceptions.h"
 
 #include <cmath>
 #include <cstring>
@@ -152,12 +153,14 @@ void Group::assign(int narg, char **arg)
   // add a new group if igroup = -1
 
   int igroup = find(arg[0]);
+  bool created = false;
 
   if (igroup == -1) {
     if (ngroup == MAX_GROUP) error->all(FLERR,"Too many groups");
     igroup = find_unused();
     names[igroup] = utils::strdup(arg[0]);
     ngroup++;
+    created = true;
   }
 
   double **x = atom->x;
@@ -165,6 +168,7 @@ void Group::assign(int narg, char **arg)
   int nlocal = atom->nlocal;
   int bit = bitmask[igroup];
 
+  try {
     // style = region
     // add to group if atom is in region
 
@@ -509,6 +513,16 @@ void Group::assign(int narg, char **arg)
 
     } else error->all(FLERR,"Illegal group command");
 
+  } catch (LAMMPSException & e) {
+    // undo created group in case of an error
+    if (created) {
+      delete [] names[igroup];
+      names[igroup] = nullptr;
+      ngroup--;
+    }
+    throw e;
+  }
+
   // print stats for changed group
 
   int n;

unittest/commands/test_groups.cpp

@@ -297,7 +297,7 @@ TEST_F(GroupTest, Dynamic)
     command("group grow delete");
     command("variable ramp equal step");
     END_HIDE_OUTPUT();
-    ASSERT_EQ(group->ngroup, 4);
+    ASSERT_EQ(group->ngroup, 3);
 
     TEST_FAILURE(".*ERROR: Group dynamic cannot reference itself.*",
                  command("group half dynamic half region top"););