Memory Allocation Exception in Constructor

Question

I have a constructor that allocates several blocks of memory using the new operator.

X::X() {
    a = new int[100];
    b = new char[100];
    c = new float[100];
}

My question is, if the allocation of c fails, and the constructor throws an exception, will the memory for a and b be automatically freed?

Answer 1

The memory to which a and b point would not be automatically freed. Every new[] must be balanced explicitly with a delete[].

Even if your destructor performed the deletion (assuming a, b, and c are class members), then you'd still leak memory. That's because the destructor wouldn't be called in this case since the object failed to construct.

Using std::vectors would obviate these problems.

Answer 2

a, b, and c will all be destroyed. Depending on what types they are, that might or might not release the memory. If they are pointers their destructors don't do anything, and the memory leaks. If they are some sort of smart pointer, presumably their destructors will release the memory.