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c++pointersnullexc-bad-access

Setting pointer to NULL fixes project

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.

Solution

  • 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.