Locate Memory Leaks in C/C++ Development on Mac OS

Introduction

Memory leaks can significantly impact the performance of C++ applications. In this article, we will explore the process of identifying and fixing memory leaks in C++ development on Mac OS. We'll start with a simple C++ program containing a memory leak, demonstrate how to use the "leaks" tool to identify and fix the issue and introduce the usage of smart pointers for more robust memory management.

By following this guide, you will gain practical insights into detecting, resolving, and preventing memory leaks in your C++ code, ultimately improving the reliability and performance of your software applications on Mac OS.

Intentional Memory Leak Example

// memory_leak_example.cpp
#include <iostream>

int main() {
    int* p = new int[99];

    // Filling the array
    for(auto i = 0; i < 99; ++i) {
        p[i] = i * 10;
    }
    // Printing all elements
    for(auto i = 0; i < 99; ++i) {
        std::cout << p[i] << '\n';
    }
    // Intentional memory leak
}

In this example we are allocating memory dynamically for array of 99 integers inside main(). But we are not releasing or deallocating those memory. Which leads to memory leak.

How To Identify leak in MAC OS

Use leaks tool present in MAC OS. It helps identifying the spot which makes memory leak. But it needs debug binary. So we should build our binary using debug flag.

Debugging with the "leaks" Tool

On Mac OS, the "leaks" tool is a powerful utility for detecting memory leaks in C++ programs. To use the "leaks" tool, follow these steps:

1. Compile the program with debugging symbols enabled:

   clang++ -g -o memory_leak_example memory_leak_example.cpp

1. Run the program with the "leaks" tool:

leaks --atExit --list -- ./memory_leak_example

1. Output:

2.    leaks Report Version: 3.0
      Process 7298: 189 nodes malloced for 15 KB
      Process 7298: 1 leak for 416 total leaked bytes.
   
      Leak: 0x12c7040f0  size=416  zone: MallocStackLoggingLiteZone_0x1006d0000   malloc in main  C  memory_leak_example
              Call stack: 0x18be910e0 (dyld) start | 0x10011b208 (memory_leak_example) 
      main  memory_leak_example.cpp:5 | 0x18c1c6528 (libc++abi.dylib) operator new(unsigned long) | 0x18c04ea44 (libsystem_malloc.dylib) _malloc_zone_malloc_instrumented_or_legacy
   

From the above output it is clear that there is 0ne memory leak by looking into following log. Process 7298: 1 leak for 416 total leaked bytes. Also the line number can be identified from looking following log. main memory_leak_example.cpp:5

The "leaks" tool provides information about the memory leaks in the program, including the size of the leaked memory and other relevant details.

Fixing the Memory Leak

Use delete[] in main() to fix this issue and recheck with leaks tool.

// memory_leak_example.cpp
#include <iostream>

int main() {
    int* p = new int[99];

    // Filling the array
    for(auto i = 0; i < 99; ++i) {
        p[i] = i * 10;
    }
    // Printing all elements
    for(auto i = 0; i < 99; ++i) {
        std::cout << p[i] << '\n';
    }

    delete[] p;
}

Now run build using -g flag and then run the leaks tool. Below is the commandline output which shows there is no memory leak.

----

leaks Report Version: 3.0
Process 7588: 188 nodes malloced for 14 KB
Process 7588: 0 leaks for 0 total leaked bytes.

ASSIGNMENT:

Use smart_pointer and check.

Happy learning and coding!