EECS 280 Tutorials

Leaking Checking

This tutorial explains how to check for memory leaks in C/C++ programs. We’ll use the address sanitizer on WSL and Linux and the leaks tool on macOS.

Quick start

WSL or Linux: Add the compiler flag -fsanitize=address in the Makefile. Compile and run.

CXXFLAGS ?= -Wall -Werror -pedantic -g --std=c++17 -Wno-sign-compare -Wno-comment
# primer-spec-highlight-start
CXXFLAGS += -fsanitize=address
# primer-spec-highlight-end
$ make main.exe
$ ./main.exe

macOS: Compile and run with the leaks tool. Not compatible with the address sanitizer (remove compiler flag -fsanitize=address).

$ make main.exe
$ MallocStackLogging=1 leaks -quiet -atExit -- ./main.exe


This tutorial relies on command line tools. If you haven’t installed CLI tools on your machine yet, follow one of these tutorials first.

macOS Windows Linux

We’re also assuming you are familiar with a text editor or IDE. If you haven’t already done so, follow one of these tutorials.

VS Code (recommended) Visual Studio Xcode

Finally, you’ll need to be familiar with the command line interface (CLI). If you haven’t seen it yet, take a look at the Command Line Tutorial.

Example program

We’ll work in a directory called leakcheck just for this tutorial.

$ mkdir leakcheck

Create a file called main.cpp and copy-paste this leaky Hello World program.

#include <iostream>
using namespace std;

int main() {
  new int;  // Memory leak!
  cout << "Hello Leaks!\n";

Create a file called Makefile and copy-paste this code.

CXX ?= g++
CXXFLAGS ?= -Wall -Werror -pedantic -g --std=c++17 -Wno-sign-compare -Wno-comment

# Run regression test
test: main.exe

# Compile the main executable
main.exe: main.cpp
	$(CXX) $(CXXFLAGS) main.cpp -o main.exe

# Remove automatically generated files
clean :
	rm -rvf *.exe *~ *.out *.dSYM *.stackdump

Your directory should look like this:

$ tree
├── Makefile
└── main.cpp

The program should compile and run.

$ make main.exe
$ ./main.exe
Hello Leaks!


Verify that your Makefile does not enable the address sanitizer.

CXXFLAGS ?= -Wall -Werror -pedantic -g --std=c++17 -Wno-sign-compare -Wno-comment
# primer-spec-highlight-start
# Should *not* see -fsanitize=address
# primer-spec-highlight-end

Compile and run with the leaks program.

$ make main.exe
$ MallocStackLogging=1 leaks -quiet -atExit -- ./main.exe
main.exe(14025) MallocStackLogging: could not tag MSL-related memory as no_footprint, so those pages will be included in process footprint - (null)
main.exe(14025) MallocStackLogging: recording malloc and VM allocation stacks using lite mode
Hello Leaks!
Process 14025 is not debuggable. Due to security restrictions, leaks can only show or save contents of readonly memory of restricted processes.

leaks Report Version: 4.0, multi-line stacks
Process 14025: 226 nodes malloced for 17 KB
Process 14025: 1 leak for 16 total leaked bytes.

STACK OF 1 INSTANCE OF 'ROOT LEAK: <malloc in main>':
3   dyld                                  0x1aea9be50 start + 2544
2   main.exe                              0x1001bf220 main + 16  main.cpp:0
1   libc++abi.dylib                       0x1aed808b0 operator new(unsigned long) + 32
0   libsystem_malloc.dylib                0x1aec2ec20 _malloc_zone_malloc_instrumented_or_legacy + 128 
    1 (16 bytes) ROOT LEAK: <malloc in main 0x12e7040f0> [16]

WSL and Linux

Edit your Makefile and enable the address sanitizer by adding -fsanitize=address.

CXXFLAGS ?= -Wall -Werror -pedantic -g --std=c++17 -Wno-sign-compare -Wno-comment
# primer-spec-highlight-start
CXXFLAGS += -fsanitize=address
# primer-spec-highlight-end

Compile and run.

$ make main.exe
$ ./main.exe
Hello Leaks!

==1905936==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 4 byte(s) in 1 object(s) allocated from:
    #0 0x7f54a90ae7b0 in operator new(unsigned long) (/lib64/
    #1 0x400a73 in main /home/awdeorio/leakcheck/main.cpp:6
    #2 0x7f54a8303cf2 in __libc_start_main (/lib64/

SUMMARY: AddressSanitizer: 4 byte(s) leaked in 1 allocation(s).

CAEN Linux Pitfall On Michigan Engineering CAEN Linux, you may need to load a full-featured GCC with the module tool. You’ll need to do this each time you log in.

$ module load gcc/9


Original document written by Andrew DeOrio

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