Fix memory leak in BaseException (and derived exceptions)

src/storm/exceptions/BaseException.cpp

@@ -19,11 +19,8 @@ namespace storm {
 		}
         
         const char* BaseException::what() const NOEXCEPT {
-            std::string errorString = this->stream.str();
-            char* result = new char[errorString.size() + 1];
-            result[errorString.size()] = '\0';
-            std::copy(errorString.begin(), errorString.end(), result);
-            return result;
+            errorString = this->stream.str();
+            return errorString.c_str();
         }
     }
 }

src/storm/exceptions/BaseException.h

@@ -46,6 +46,10 @@ namespace storm {
         protected:
             // This stream stores the message of this exception.
             std::stringstream stream;
+
+        private:
+            // storage for the string backing the C string returned by what()
+            mutable std::string errorString;
         };
         
     } // namespace exceptions