The central concept.
WHAT A POINTER IS
A variable holding a memory address.
WHY THEY EXIST
To access memory directly, pass large structures cheaply, and build dynamic data structures.
WHAT THE STACK IS
Memory for local variables, allocated and released automatically as functions are entered and left.
WHAT THE HEAP IS
Memory allocated explicitly, released explicitly.
WHAT GOES WRONG
Allocating and never freeing, leaking memory Freeing and then using, producing undefined behaviour Freeing twice Writing beyond an allocation, corrupting adjacent memory Returning a pointer to a local variable, which no longer exists
WHY UNDEFINED BEHAVIOUR IS DANGEROUS
The program may appear to work, and fail unpredictably later.
WHAT DISCIPLINE HELPS
Every allocation paired with its release Setting pointers to null after freeing Checking every allocation succeeded Bounds checked explicitly, always
WHAT TOOLS FIND
Leaks, invalid access and undefined behaviour, at runtime.
WHAT TO ALWAYS RUN
Those tools, during development.
WHAT TO NEVER ASSUME
That code without warnings is correct.
