How Does `delete[]` Know How Many Elements to Delete from an Array?

How does delete[] Decipher an Array

The code in question:

void deleteForMe(int* pointer)
{
     delete[] pointer;
}

has undefined behavior if the pointer is not pointing to an array, as it blindly performs a delete[] operation. However, when the pointer references an array, as in:

int main()
{
     int* arr = new int[5];
     deleteForMe(arr);
     return 0;
}

the OS somehow knows to only delete the specified array elements and not proceed beyond them.

The key to this behavior lies in C 's historical roots as a C-compatible language. To avoid burdening programmers who do not use arrays with unnecessary overhead, the delete[] syntax was introduced.

When a non-array allocation is made, such as:

Foo* foo = new Foo;

no extra overhead is incurred for array support. However, for array allocations, this overhead does exist. To indicate that the runtime libraries should use this information, the programmer must specify delete[] for array pointers.

Thus, the choice between delete and delete[] is based on the specific allocation being deleted. This allows for finer-grained memory management and aligns with C 's philosophy of minimalism.

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