How to know whether the TStringList was newed

Question

I am using C++ Builder XE4 on Windows7 Professional (32bit).

I have a question on TStringList;

What I would like to do is to know whether the TStringList variable was newed or not, to prevent Add() method to non-newed TStringList;

I thought checking NULL might work, but it didn't.

TStringList *list;
// list = new TStringList();  // someone commented out by mistakes

if (list == NULL) {
    ShowMessage(L"NULL");
} else {
    ShowMessage(L"not empty");
}
return;

The above code shows "not empty" dialog.

What is a standard way to check the newed or non-newed TStringList?

Answer 1

It is very commonplace is c/c++ to initialize pointers to NULL, and have them be null whenever they aren't pointing at something valid.

As such, your if statement is a very commonplace and appropriate piece of code.

However, this does require initializing your variable.

Unless declared at global/file scope, the line: TStringList *list; does not initialize the variable to any specific value - this leaves it pointing at random crap.

You need to change it to TStringList *list = NULL; (or similar, some people dont like "NULL")