How do I use Valgrind to find memory leaks?

Valgrind includes an option to check for memory leaks. With no option given, it will list a heap summary where it will say if there is any memory that has been allocated but not freed. If you use the option –leak-check=full it will give more information.

How do you read Valgrind?

Valgrind is a program that checks for both memory leaks and runtime errors. A memory leak occurs whenever you allocate memory using keywords like new or malloc, without subsequently deleting or freeing that memory before the program exits.

What is leak summary in Valgrind?

The Leak Summary tells you what memory your program might have leaked. Anything lost means that some heap allocated memory can no longer be reached by your program. In general, you do not want to lose track of any memory. The Error Summary tells you how many errors occurred during the execution of your program.

Why is Valgrind so slow?

According to Valgrind Manual, Valgrind will very noticeably slow down your application: The amount of instrumentation code added varies widely between tools. At one end of the scale, Memcheck adds code to check every memory access and every value computed, making it run 10-50 times slower than natively.

Can Valgrind be wrong?

Yes, there are false positives with Valgrind, that’s why it has suppression files for particular glibc and gcc versions, for example. The false positives may arise if you are using older valgrind with newer gcc and glibc, i.e., valgrind 3.3 with glibc 2.9.

How do I set up Valgrind?

You can do this by following the instructions at DebuggingProgramCrash.

Make sure Valgrind is installed. sudo apt-get install valgrind.
Remove any old Valgrind logs: rm valgrind.log*
Start the program under control of memcheck:

What are valgrind errors?

Valgrind reports two types of issues: memory errors and memory leaks. When a program dynamically allocates memory and forgets to later free it, it creates a leak. A memory leak generally won’t cause a program to misbehave, crash, or give wrong answers, and is not an urgent situation.