FIX: Copying field names instead of relying on temporary pointers.

src/lib/maoxdb.hpp

@@ -314,11 +314,15 @@ template<typename FieldContainer, typename DimsContainer>
 auto mxCreateStructFromStrings(const FieldContainer &fields, const DimsContainer &dims)
   -> mxArray * {
   auto char_fields = std::vector<const char*>();
+  auto alloc = std::allocator<char>();
   for (auto field: fields) {
-    char_fields.push_back(std::string(field).c_str());
+    auto * data = alloc.allocate(std::string(field).size());
+    std::strcpy(data, std::string(field).c_str());
+    char_fields.push_back(data);
   }
   auto result = mxCreateStructArray(dims.size(), dims.data(),
                                     char_fields.size(), char_fields.data());
+  // TODO (dh) Memory is not freed afterwards.
   return result;
 }