读取向量迭代器访问错误

Question

I have a vector<int> called pitches . I'm getting periodic bad access on the last line below:

int play = 0;
bool didFind = 0;
vector<int>::const_iterator iterator;

for (iterator = pitches.begin(); iterator != pitches.end(); ++iterator) {
    if (*iterator > lastpitch) { // lastpitch is an int
        didFind = 1;
        play = *iterator;
        break;
    }
}

if (!didFind) play = *(pitches.begin()); // this line gives me bad access

I had previously tried *pitches.begin() on the last line but that always provided bad access and I understand that now. But while I get it less often now, this play=*(pitches.begin()); is still doing the same occasionally. I cannot see anything in the above that would cause that, any suggestions appreciated.

Answer 1

If pitches vector has size 0 , the things inside

      for (iterator=pitches.begin();iterator!=pitches.end();++iterator)

doesn't get executed and therefore didFind=0 .

The statement inside if is evaluated. Yet pitches is empty means pitches.begin()==pitches.end() . Dereferencing a pitches.end() is to access out of bound and therefore gives bad access .