How do you fix buffer overflow?

Answer 1

The problem with buffers is that you need to keep track of the amount of memory physically allocated to the buffer. This means a buffer has at least two variables: a reference to the allocation and its size. If the buffer size is constant it is obviously easier to keep track of its length but if it is variable you must ensure the size variable is kept in sync with the actual buffer length. The easiest way to keep track of buffer lengths is to store the buffer and its length in a structure:

struct data {

char * buffer;

int length;

};

You still have to ensure the length is kept in sync with the buffer, but now the two can be treated as being a single entity, making it much easier to pass buffers into and out of functions.

However, a better approach is to use object-oriented programming to encapsulate the buffer and its length, thus hiding the details of the representation:

std::vector<char> buffer;

You no longer have to keep track of the length because that is encapsulated within the vector. Every time you push/pop values, the size is incremented or decremented accordingly. All memory management is also handled by the vector, so new memory is allocated as and when required, and the size is adjusted accordingly. All you have to do is rewrite your functions to make use of a vector rather than a buffer.