On a semi-large project (~5000 lines of code)...

I have a class with a pointer as one of its fields. The pointer was declared but not initialized:

Apple *apple;

In the class's constructor, I initialized the pointer if it was NULL:

if (apple == NULL) {
    apple = new Apple();
}

Further down in the project's code, I did:

apple->color = "red";

The program worked fine for months, until today it gave me a EXC_BAD_ACCESS error, because the apple pointer was not explicitly initialized to NULL and started out with some garbage value - so the NULL check failed, and dereferencing it gave a EXC_BAD_ACCESS.

So my question is - how did the program work fine for months? Was the pointer set to NULL previously by pure luck?

Note: I made no changes to the code here, only changes elsewhere in the project that didn't touch this/seem irrelevant.

CodePudding user response：

1. In a constructor, you don't need to check for "previous" state of the variables, just set it to what you need, unconditionally.

2. Are you sure you want a pointer to Apple and not that object itself? If you had in your class

   Apple apple;

it would be default-constructed for you, and you won't need to explicitly delete it (that you may forget, leaking memory).

CodePudding user response：

It's hard to tell decisively, but probably yes, the program worked by sheer luck.

If you don't explicitly initialize a pointer you can't assume anything about it, and TBH, it's not surprising that the program started crashing, but that it worked up until now.