Dynamic Memory Management
Allocate a runtime-sized array and release it safely.
What is Dynamic Memory Management?
Dynamic storage is needed when an object's size or lifetime cannot be fixed at compile time.
Important points
- Every pointer must refer to a live compatible object or be null.
- Pair each owned allocation with exactly one release.
- Prefer clear ownership and const-correct interfaces.
C and C++ code examples
main.c
#include <stdio.h>
#include <stdlib.h>
int main(void) {
size_t count = 5;
int *values = calloc(count, sizeof *values);
if (!values) return 1;
for (size_t i = 0; i < count; ++i) values[i] = (int)(i * i);
printf("last=%d\n", values[count - 1]);
free(values);
return 0;
}
last=16C++
main.cpp
#include <iostream>
#include <vector>
int main() {
std::vector<int> values(5);
for (std::size_t i = 0; i < values.size(); ++i) values[i] = static_cast<int>(i * i);
std::cout << "last=" << values.back() << '\n';
}
last=16C and C++ comparison
C requires matching calloc or malloc with free and checking allocation failure. A C++ vector owns its memory, releases it automatically, and remains safe if an exception occurs.
C
Ownership and cleanup are conventions enforced by the programmer.
C++
Containers and RAII types can encode ownership and cleanup in object lifetimes.
Practice exercises
Run both versions, then modify them to observe the different language guarantees.
- Test null and allocation-failure paths.
- Run with AddressSanitizer and UndefinedBehaviorSanitizer.
- Document whether every pointer owns or only observes its object.
Practice with a challenge
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