Question

In my header file I declare a variable within the scope of a class:

    FaultModel<double>   *fm_req_set_odom_px;

…which is conditionally initialised in the class constructor, depending on the value of a configuration file:

    const char *configModel = ConfigReader->ReadString("FaultModel");
    if (strcmp(configModel, "cyclic") == 0)
        fm_req_set_odom_px = new CyclicFaultModel<double>();

My question is: do I need to wrap the delete with a conditional to check if the model was initialised or not, or is it safe to just delete it in either case?

   if (fm_req_set_odom_px != NULL) // Is this necessary?
       delete fm_req_set_odom_px;

Answer 1

delete NULL; is guaranteed to be a no-op, so a manual check is not necessary. However, an unitialized pointer variable is not NULL, so you must explicitly set it to NULL if the condition fails:

if (strcmp(configModel, "cyclic") == 0)
    fm_req_set_odom_px = new CyclicFaultModel<double>();
else
    fm_req_set_odom_px = NULL;

Alternatively, you can set the pointer variable to NULL unconditionally before the if statement:

fm_req_set_odom_px = NULL;
if (strcmp(configModel, "cyclic") == 0)
    fm_req_set_odom_px = new CyclicFaultModel<double>();