How to install valgrind on windows

How to build and run Valgrind for Windows from a command prompt

  1. Check out the source code.
  2. Open a Windows command prompt (cmd.exe)
  3. cd to the source code directory.
  4. run: sh ./autogen.sh.
  5. configure either for the 32 bit or 64 bit version. …
  6. build the source by running: make.
  7. build tests by running: make check.
  1. Can you run Valgrind on Windows?
  2. How do you set up a Valgrind window?
  3. Where can I find Valgrind executable?
  4. How do I run Valgrind locally?
  5. Can we attach Valgrind to a running process?
  6. How do I run Valgrind on WSL?
  7. What is the difference between valgrind and GDB?
  8. What is valgrind C++?
  9. Why does valgrind not work on Mac?
  10. Does Valgrind work on WSL?
  11. How do I use Dr memory in Windows?
  12. How do you detect a memory leak in CLion?

Can you run Valgrind on Windows?

Valgrind is a developer tool for C++ developers used to find memory issues including C++ memory leak detection. … Valgrind heavy relies on Linux internals, that’s why Valgrind does not support Windows.

How do you set up a Valgrind window?

press win+s to open Cortana. search for windows features , open Turn Windows features On or Off. find Windows Subsystem for Linux (Beta) , click to turn it on. After a restart you could now open your windows command line and input bash , then enter.

Where can I find Valgrind executable?

SOLVED Valgrind executable? There is a field of settings of Analizer > Generic Settings > Valgrind executable.

How do I run Valgrind locally?

To run Valgrind, pass the executable as an argument (along with any parameters to the program). The flags are, in short: —leak-check=full : «each individual leak will be shown in detail» —show-leak-kinds=all : Show all of «definite, indirect, possible, reachable» leak kinds in the «full» report.

Can we attach Valgrind to a running process?

Therefore Memcheck does not support eager checking at this time. 5.4. Is it possible to attach Valgrind to a program that is already running? No.

How do I run Valgrind on WSL?

Make: simply launch make while in the valgrind-3.12. 0 folder. Check the dependencies: launch make check to see whether all the dependencies necessary for the installation are satisfied (e.g: you’ll have to install g++, just launch sudo apt install g++ ) Install valgrind: type sudo make install to install it.

What is the difference between valgrind and GDB?

The GNU Debugger (GDB) allows you to pause a running program and inspect its state. Valgrind’s memcheck monitors a program’s memory accesses and prints warnings if the program accesses invalid locations or attempts to read values that the program never set (initialized).

What is valgrind C++?

valgrind is a tool for finding memory access errors to heap memory (memory that is dynamically allocated with new or malloc) in C and C++ programs. … Tools like valgrind can save you days worth of debugging time by quickly pointing you to the source and type of memory access errors in your code.

Why does valgrind not work on Mac?

However, the sad news is, even the most recent version of Valgrind is not very usable on Mac OS Sierra. The reason is that Apple has not released the part of the source code that makes Valgrind crash, without which, the Valgrind maintainers can hardly do anything.

Does Valgrind work on WSL?

Now that everything is ready you must configure CLion in order to be able to use the CMake of WSL and then valgrind. In File > Settings > Toolchains, click on Add (+) and select WSL.

How do I use Dr memory in Windows?

Invoking Dr.

Run your application as you normally would from a command prompt (on Windows, either the cmd shell or a Cygwin prompt), with drmemory and «—» prefixed to the command line (the «—» separates any arguments to Dr. Memory from the application being run).

How do you detect a memory leak in CLion?

On Linux and macOS platforms CLion integrates with Valgrind Memcheck to help you detect memory errors. It lets you run targets with Valgrind Memcheck and then get the results in a special tab in the Run tool window. Users can run both regular targets and unit tests targets with Memcheck.

Valgrind is a famous tool to debug your memory leak, but what sad is it only supports Linux, yeah, not a perfect support even on Mac. But with the new Windows 10 Anniversary update, it’s happening. And works way much better than Mac with OS X. Let’s rock!

1. What, Linux in a Windows?

It is easy since in the new update, windows has Ubuntu as a subsystem. And it is neither a virtual machine nor some kind of a container. It is a subsystem, roughly speaking, all the functions will finally invoked by Windows sys-call. So this is a 1st class, blazing fast solution. But the prerequisite is you need a new Windows 10 version 1607 (Build 14393.187) or above.

2. How to install and use it?

When you search online, you will find that you need to join the Windows Insider program and open the developer mode. But no, you don’t need to.

  1. press win+s to open Cortana.
  2. search for windows features, open Turn Windows features On or Off.
  3. find Windows Subsystem for Linux (Beta), click to turn it on.
  4. After a restart you could now open your windows command line and input bash, then enter.
  5. It will first download and install Ubuntu 14.04 from Windows store.
  6. Then you need to configure your default user and password to the system. This is just for this built-in Ubuntu, not Windows
  7. Afterwards, every time you need bash, you just open CLI then bash and enter, splendid!

3. Try it first time.

It is a Ubuntu, so you might simply use the command. sudo apt-get install valgrind. Yes, it will work as a charm. But only for this part. If you want to use it, it will totally not work.

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--1791:0:aspacem -1: ANON 0038000000-00383d5fff 4022272 r-x-- SmFixed d=0x000 i=205168 o=0 (0) m=0 /usr/lib/valgrind/memcheck-amd64-linux
--1791:0:aspacem Valgrind: FATAL: aspacem assertion failed:
--1791:0:aspacem segment_is_sane
--1791:0:aspacem at m_aspacemgr/aspacemgr-linux.c:1502 (add_segment)
--1791:0:aspacem Exiting now.

You may abort at this stage, since it is a beta feature, and the translation in the Sys-call level may seems a big deal. And after googling, you decide to abort. But, the story never ends like this :)

4.How to deal with it?

A brief first:

You just need to compile Valgrind by yourself on your own machine.”

The idea is simple, the procedures is still easy but take a little bit longer than expected. But I will cover all the commands :)

  1. Open bash in Windows.
  2. Update your Ubuntu package lists by sudo apt-get update
  3. Install SVN first via this command: sudo apt-get install svn
  4. Install subversion next: sudo apt-get install subversion (Thanks to Ran Lottem)
  5. Find a folder you want to put the valgrind, anywhere is OK, we just need to compile.
  6. Download source code of Valgrind via SVN svn co svn://svn.valgrind.org/valgrind/trunk valgrind. It will download the codes and put them into a new folder called valgrind right under then folder you create or locate in step 3.
  7. Install the library used when compiling by sudo apt-get install automake
  8. Ran Lottem confirmed that you need to sudo apt-get install build-essential
  9. Go to the folder of Valgrind via cd valgrind/
  10. Running the official bash script first by using ./autogen.sh
  11. Configure via ./configure.
  12. From now on, things will get much more normal. first, install make via sudo apt-get install make.
  13. Then make, this command will build the files from many modules. Add sudo if failed (Thanks Waleed Mahmoud).
  14. make install, it will copy compiled files into appropriate locations. Add sudo if failed (Thanks Waleed Mahmoud).
  15. It’s done already, but feel free to use make clean, it will delete all the temporary files generated while compiling.
  16. A make distclean will make things much better.
  17. Use valgrind as you wish.

5.Happily ever after

I have built a linked list to test the leak, it works exactly the same way as linux, even better than Mac, OS X, yes, I mean it. The valgrind on OS X will tell you have some leak problems while there is no leak.

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camus@ALBERTSURFACEB:/mnt/d/github/C_Playground$ valgrind ./main
==2529== Memcheck, a memory error detector
==2529== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==2529== Using Valgrind-3.12.0.SVN and LibVEX; rerun with -h for copyright info
==2529== Command: ./main
==2529==

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==2529==
==2529== HEAP SUMMARY:
==2529== in use at exit: 0 bytes in 0 blocks
==2529== total heap usage: 6 allocs, 6 frees, 104 bytes allocated
==2529==
==2529== All heap blocks were freed -- no leaks are possible
==2529==
==2529== For counts of detected and suppressed errors, rerun with: -v
==2529== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)
camus@ALBERTSURFACEB:/mnt/d/github/C_Playground$

And if you have a leak, it will tell you.

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==2539== HEAP SUMMARY:
==2539== in use at exit: 80 bytes in 5 blocks
==2539== total heap usage: 6 allocs, 1 frees, 104 bytes allocated
==2539==
==2539== LEAK SUMMARY:
==2539== definitely lost: 16 bytes in 1 blocks
==2539== indirectly lost: 64 bytes in 4 blocks
==2539== possibly lost: 0 bytes in 0 blocks
==2539== still reachable: 0 bytes in 0 blocks
==2539== suppressed: 0 bytes in 0 blocks
==2539== Rerun with --leak-check=full to see details of leaked memory
==2539==
==2539== For counts of detected and suppressed errors, rerun with: -v
==2539== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

Furthermore, running valgrind --leak-check=full ./main will give the information of your stack. WOW! Fantastic! After I suffered so much from day 1 for the stupid Surface Book, this is the only time I feel Microsoft is a company you could rely on, haha xD

6. One more thing

Mr Artem reached out to me recently about his awesome software for debugging memory issues. He built Deleaker, which is a modern substitution of
Valgrind. Deleaker supports C as well as C++/Delphi/.Net etc. In general, it doesn’t matter what language is used to write code as it works at lower level, hooking allocation/deallocation functions and storing call stacks.

And having a nice GUI to work with just seems much more efficient to me, which is why I love jetBrains’ products.

  • Check this blog for a comparison between Deleaker and Valgrind, why it is better.
  • Check the Deleaker official site for more information.

Thanks for reading!

Follow me (albertgao) on twitter, if you want to hear more about my interesting ideas.

We’ll be programming the language C. In particular, we’re using the C compiler clang, and the memory debugging tool valgrind. The preferred approach for doing this is to use Repl.it. You don’t have to install anything locally on your own computer to do so. Most importantly, Repl.it allows you to pair program remotely simultaneously with others, and also share your code with us in real-time so that we can help you diagnose problems as you are working on them.

However, if you find that you wish to also install C / Valgrind locally on your computer, you might be able to. Using C is generally straightforward on most of the operating systems we’re using. Valgrind, unfortunately, isn’t practically usable on Macs for purposes of this course. I have instructions below for various operating systems. I want to again emphasize that Repl.it is the primary approach that we’re using, and it will be much more difficult for us to support you remotely if you only install it locally. But I also understand that you may experience connection issues which may push you towards a local install.

Ubuntu Linux

The following instructions are for Ubuntu; if you are using an alternative Linux distribution, you’ll need to figure out how to adapt accordingly. At a terminal prompt, enter the following:

sudo apt update && sudo apt upgrade
sudo apt install clang
sudo apt install valgrind

Windows

clang and Valgrind on Windows are supported via Windows Subsystem for Linux (WSL). If you haven’t already installed WSL on your computer, see the instructions at the Microsoft WSL installation site. If you are doing this for the first time, select Ubuntu 20.04 LTS. Once it has been installed, start WSL by typing Ubuntu into the Windows search bar. This will give you a terminal window. To install C and Valgrind within, follow the instructions in the Ubuntu Linux section above.

Macs

Sadly, Macs are more cumbersome to get working properly than the other operating systems above, for a variety of reasons that I’m happy to discuss if people want to follow up with questions. clang is straightforward enough; Valgrind is a problem.

Installing clang, which is the C compiler

clang is included within Apple’s Command Line Tools. Here are instructions on how to install. Once this process is done, open a terminal window, and type clang and hit enter. If you see something like:

$ clang
clang: error: no input files

… then clang is installed and working correctly.

Installing Valgrind, which is the memory diagnostic and debugging tool

Valgrind is a critical tool that we’ll be using. It tells us if there are invisible memory errors in your code that you might not know about, which cause unpredictable behavior in your code. There are two problems with installing Valgrind on Macs.

  1. The Valgrind team is slow to adapt it to current versions of OS X, and it’s never quite clear which versions of the operating system it will work for.

  2. It tells you that there are memory bugs in perfectly acceptable programs, for a complicated set of reasons. Professional developers who use Valgrind on Macs work hard over time to curate a suppressions file with a list of memory bugs that are spurious and thus ignorable for their own code. This supppresions file doesn’t stay consistent for different versions of OS X. Maintaining such a suppressions file sadly isn’t practical for this course.

So in short, don’t do it. You might succeed at getting Valgrind to install via Homebrew; that depends on which version of OS X you have. But see #2 above: you won’t get output from it that’s believable. A number of students in past versions of this class have tried to make this work, and every time they walk away frustrated.

So how do you proceed? If you must work locally on a Mac, don’t use Valgrind locally. Instead, I will have the GitHub auto tests set up to run Valgrind tests. You’ll get reliable Valgrind testing done on GitHub’s Linux testing servers. Unfortunately, the process is slow. You’ve already been watching the auto-testing process; you’ll have to wait for the tests to complete before you can see where the errors are happening. But it’s better than nothing.

But I want to say directly two things, which are frustratingly nearly inconsistent with each other:

  • Using Valgrind is critical for this course, and to be correct you must run Valgrind tests on your code.
  • Installing Valgrind locally on a Mac is something of a disaster, and something you should avoid.

So if you’re on a Mac, use Repl.it for Valgrind testing if you at all can. If you can’t, then use the results from GitHub autotesting.

And feel free to follow up on the Moodle Q&A if you want more info as to why Macs are such a problem for Valgrind.

Valgrind on Windows: A Powerful Tool for Debugging and Memory Management

Valgrind, a powerful open-source tool for memory leak detection, memory error detection, and performance profiling, is commonly associated with Linux environments. However, it’s possible to harness its benefits on Windows, thanks to a project known as «Valgrind for Windows». This article will guide you through the process of setting up and using Valgrind on Windows to enhance your software development workflow.

Why Valgrind Matters

Memory leaks and other memory-related errors can be a developer’s worst nightmare. They can cause crashes, unpredictable program behavior, and security vulnerabilities. Valgrind excels at identifying these issues early in the development cycle, preventing them from impacting your users. Here’s why Valgrind is a valuable tool for any Windows developer:

  • Memory Leak Detection: Valgrind’s Memcheck tool meticulously tracks memory allocations and deallocations. It flags potential memory leaks, where memory is allocated but never released, potentially leading to resource depletion and system instability.
  • Memory Error Detection: Valgrind’s Memcheck also detects other memory-related errors like invalid memory accesses (reading or writing to memory locations you shouldn’t) and use-after-free errors, where you attempt to access a memory region that has been freed.
  • Performance Profiling: Valgrind’s Callgrind tool profiles your code’s performance, identifying bottlenecks and areas where optimization can significantly improve execution speed.

Getting Started with Valgrind on Windows

1. Installing the Valgrind for Windows Package

The easiest way to get Valgrind running on Windows is by downloading the «Valgrind for Windows» package from the Valgrind for Windows website. This package includes Valgrind itself, along with the required dependencies and tools for a smooth integration.

2. Choosing the Right Version

Several Valgrind versions are available for different architectures and operating systems. Select the version that aligns with your project’s requirements and Windows environment. The «Valgrind for Windows» package typically provides a 32-bit and 64-bit version, so you’ll need to choose the correct version for your project.

3. Integrating Valgrind into Your Development Environment

Once installed, you can integrate Valgrind into your favorite development environment, like Visual Studio or CodeBlocks. Here’s a simple example using Visual Studio:

  1. Create a new project or open an existing one.
  2. Set the path to Valgrind: In your project’s build settings, specify the directory containing the Valgrind executable.
  3. Add a pre-build step: This step should invoke Valgrind to run your application with the desired analysis.

4. Running Your Application with Valgrind

After setup, run your application through Valgrind by using the Valgrind command-line tool. For example, if your executable is called «myprogram.exe»:

valgrind --tool=memcheck --leak-check=full myprogram.exe

This command instructs Valgrind to use the Memcheck tool with full leak checking for your «myprogram.exe» executable.

Understanding Valgrind’s Output

Valgrind’s output can be detailed and comprehensive. It provides specific information about potential memory leaks, invalid memory accesses, and other errors. Here’s a breakdown:

  • Error messages: Valgrind will highlight the error type, its location in your code, and the specific memory address involved.
  • Memory leak reports: If leaks are detected, Valgrind provides a summary of leaked memory blocks, including their size and the function where they were allocated.
  • Performance reports: Valgrind’s performance tools, like Callgrind, provide information on the execution time of different functions, identifying bottlenecks and potential optimization areas.

Valgrind for Specific Programming Languages

While Valgrind works well with C and C++, it can also be used with other languages, including:

  • Python: The PyValgrind project provides Valgrind support for Python applications.
  • Java: Valgrind can be used to analyze Java applications with the help of a JVM-specific profiling tool.
  • C#: Valgrind can be used indirectly to analyze C# applications through the use of a tool like Valgrind for .NET.

Optimizing for Performance

While Valgrind is a powerful tool, it comes with some performance overhead. Your program’s execution will slow down when running under Valgrind. For this reason, it is typically used during development and testing, rather than in production environments.

Conclusion

Valgrind on Windows empowers developers with a powerful tool to find memory-related errors and optimize their code. By integrating Valgrind into your development workflow, you can catch bugs early, improve code quality, and release more stable and performant applications. Remember to carefully analyze Valgrind’s output, understanding the reported errors and their impact on your code. This process will help you write more robust, reliable, and high-quality software.

Installing GCC and Valgrind

  • Software And Compiler Setup
    • Setting Up Your Editing Environment
      • Recommended Text Editors
      • Honorable Mentions
      • Common Questions
    • Setting Up GCC
      • Installing GCC On Linux
      • Installing GCC On Windows
    • Setting Up Valgrind
      • Installing Valgrind On Linux
      • Installing Valgrind On Windows
    • Other Software Recommendations
      • Get A Good Console
        • Consoles For Windows
  • Using GCC And Valgrind
    • General Use Instructions
      • Compile With GCC
      • Memory Test With Valgrind
      • Basic Valgrind Output
    • Advanced Valgrind Usage
      • Debugging Segmentation Faults
      • Pinpointing Memory Leaks
  • Using Input and Output Files

Software And Compiler Setup

Setting Up Your Editing Environment

To setup your coding environment, the first thing you will need is a text editor.

Recommended Text Editors

  • Atom — Windows, Linux, Mac

    • Like Sublime, But Free, And Better
  • Notepad++ — Windows

    • Excellent Editor That Proves Looks Aren’t Everything, Only For Windows
  • Code::Blocks — Windows, Linux, Mac

    • An IDE Style, Free, Open Source Editor
  • Visual Studio Code — Windows, Linux, Mac

    • Another IDE Style, Free, Open Source Editor

Honorable Mentions

  • Sublime Text Editor — Windows, Linux, Mac

    • A Well Respected Choice, But Costs $$$
  • Eclipse — Windows, Linux, Mac

    • A Good Choice, But Far To Heavy For This Applciation
But, My Editor Isn’t Here…

  • That doesnt mean your editor is bad, it just means that some of the stuff described here might not apply to you.
What About [Insert Editor Here]

  • What about it?

Setting Up GCC

GCC is a GNU compiler for C, C++, Objective-C, Fortran, Ada, and Go.

Installing On Linux

Debian Based (Ubuntu and Derivatives)

sudo apt-get install gcc

OR

sudo apt install build-essential

Fedora 22+

dnf group install 'Development Tools'

Other

I Have No Idea - CONTRIBUTION APPRECIATED

Now Test To Make Sure It’s Working

  • Open a terminal and type in gcc -v
  • GCC should announce it’s version along with some other info
  • If GCC responded, you’re golden.

Installing On Windows

Windows 7 to 10

The easiest way to install GCC on Windows is to install MinGW, which includes GCC along with a handful of other small utilities.

Download The Latest Version of MinGW From Their Website

When running the installer for MinGW, it will install into the default folder of C:\MinGW

To make GCC work in the command line, we will need to add it to the %PATH% system variable.

To Add GCC To Your System Path:

  • Press The Windows Key On Your Keyboard
  • Type In ‘System Properties’
  • Select The Item Called SystemPropertiesAdvanced.exe
  • A Window Will Appear, At The Bottom Of This Window, Click The Button That Says Environmental Variables
  • A New Window Will Appear
  • Select ‘Path’ In The Top Portion Of The Window, Then Click Edit.
  • Yet Another Window Will Appear
  • If You Don’t See An Entry Labeled C:\MinGW\bin, Click The Add Button, And Type C:\MinGW\bin Into The Input Field That Appeared.
  • Now Test To Make Sure It’s Working
    • Open cmd and type in gcc -v
    • GCC should announce it’s version along with some other info
    • If GCC responded, you’re golden.

Windows XP

Good Luck Brave Soul - CONTRIBUTION APPRECIATED

Setting Up GCC

Installing Valgrind On Linux

Debian Based (Ubuntu and Derivatives)

sudo apt-get install valgrind

Fedora 22+

sudo dnf install valgrind

Other

I Have No Idea - CONTRIBUTION APPRECIATED

Now Test To Make Sure It’s Working

  • Open a terminal and type in valgrind --version
  • Valgrind should announce it’s version
  • If Valgrind responded, you’re golden.

Installing On Windows

Windows 10

Valgrind Cannot Be Installed Directly On Windows To The Best Of My Knowledge. That does not mean that valgrind cannot be used though Windows:

Valgrind Can Be Used On Windows Machine Using The New «Linux in a Windows» Method:

  • Linux in a Windows (Windows 10 ONLY)
    • Follow This Guide To Install The Linux Subsystem For Windows
    • Now Open The Subsystem Console And Follow The Linux Valgrind and GCC Instructions (When Using The Subsystem Console, You Will Need To Follow Linux Instructions)

Windows 7 to 8.1

  • VM Method Using VirtualBox
    • With Enough Requests I Will Write A Tutorial For This

Other Software

Get A Good Console

You will be interacting with the console a lot, so you should have one that you like.

Recommended Consoles For Windows

  • cmder
    • Built on ConEmu, offering a facelift and extra functionality.
  • ConEmu
    • Like cmder, but ugly.

Using GCC and Valgrind

General Use Instructions

Compile With GCC

GCC Command Format

Windows: gcc .\fileNameToCompile.c -o .\outputNameYouWant.exe

Linux: gcc ./fileNameToCompile.c -o ./outputNameYouWant.out

Notes On How These Are Different

  • Linux and Windows Have Different Directory Separator Characters.
    • On Windows we use \ and on Linux we use /
  • Linux and Windows Have Different output extensions.
    • On Windows we use .exe and on Linux we use .out
GCC Use On Windows

  • Open a console window
  • Use cd to get to where your .c code is How To Use cd
  • Run gcc using the format specified above
  • then enter .\outputNameYouGaveToGCCEarlier.exe, your program should start.
GCC Use On Linux (or Linux in A Windows)

  • Open a terminal window
  • Use cd to get to where your .c code is How To Use cd
  • Run gcc using the format specified above
  • then enter ./outputNameYouGaveToGCCEarlier.out, your program should start.

Memory Test With Valgrind

Once you have compiled the program with GCC, you can use valgrind to find any memory leaks. (and much more)

Valgrind Command Format

Windows: Must Use A VM or Subsystem Running Linux

Linux: valgrind ./outputNameYouGaveToGCCEarlier.out

Understanding Basic Valgrind Output

The Parts Of A Valgrind Output:

HEAP SUMMARY:

Gives an overview of the program’s memory usage during runtime.

HEAP SUMMARY:
in use at exit: 48 bytes in 3 blocks
total heap usage: 4 allocs, 1 frees, 560 bytes allocated

The Heap Summary Describes Two Parts:

  • in use at exit — Memory in use when the program exited
  • total heap usage — Total memory usage during the program run
LEAK SUMMARY:

Only appears if the program had a memory leak

LEAK SUMMARY:
definitely lost: 0 bytes in 0 blocks
indirectly lost: 0 bytes in 0 blocks
possibly lost: 0 bytes in 0 blocks
still reachable: 48 bytes in 3 blocks
suppressed: 0 bytes in 0 blocks

The Leak Summary Describes:
This List Is From The Offical Valgrind Documentation

  • definitely lost means your program is leaking memory — fix those leaks!

  • indirectly lost means your program is leaking memory in a pointer-based structure. (E.g. if the root node of a binary tree is definitely lost, all the children will be indirectly lost.) If you fix the definitely lost leaks, the indirectly lost leaks should go away.

  • possibly lost means your program is leaking memory, unless you’re doing unusual things with pointers that could cause them to point into the middle of an allocated block.

  • still reachable means your program is probably ok — it didn’t free some memory it could have. This is quite common.

  • suppressed means that a leak error has been suppressed. There are some suppressions in the default suppression files. You can ignore suppressed errors.

Advanced Valgrind Usage

Valgrind is much more than just a basic tool to test for memory leaks.

Valgrind can be used to find Segmentation Faults and Actually Locate Memory Leaks

Debugging Segfaults (SIGSEGV) (signal 11) With Valgrind

Valgrind can help find segfaults in your c code, the procedure is simple.

  • Compile your source code with the -g flag Example: gcc -g ./sourceCode.c -o ./fileName.out
  • Valgrind as described above.
This procedure links the line numbers during the compile phase. Allowing Valgrind to show the specific line number a failure occurs on.

Here’s an example:

==13268== Invalid write of size 8
==13268==    at 0x1086A8: thisFunctionDoesCauseAnIssue (valgrindtutorial.c:44)
==13268==    by 0x108625: main (valgrindtutorial.c:21)
==13268==  Address 0x0 is not stack'd, malloc'd or (recently) free'd

Suddenly, Valgrind can explain which file, function, and line an error occurred on.

Dissecting This Output:

==13268==    at 0x1086A8: thisFunctionDoesCauseAnIssue (valgrindtutorial.c:44)

==[PID]==    at [Memory Address]: [Function Name] ([Source File Name]:[Line Number])

Taking A Look At The Code:

function blamed by valgrind for segfault

Line 44 is definitely a problem, nSum->contents dereferences NULL.

Pinpoint Memory Leaks With Valgrind

Valgrind can also be used to find the source of a memory leak.

To Find The Source Of Memory Leaks With Valgrind:

  • Compile with GCC using the -g flag
  • Run Valgrind with the --tool=memcheck --leak-check=full flags.

So The Commands Would Look Like This:

Compile With GCC: gcc -g ./sourceCode.c -o ./fileName.out
Check With Valgrind: valgrind --tool=memcheck --leak-check=full ./fileName.out

This output is less strait forward than segfault recognition.
Lets Take A Look At A Sample Output:

==13422== 708 (16 direct, 692 indirect) bytes in 1 blocks are definitely lost in loss record 7 of 7
==13422==    at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==13422==    by 0x108846: createLossyNode (valgrindMemoryLeaks.c:42)
==13422==    by 0x10876B: main (valgrindMemoryLeaks.c:26)

To Better Understand This, We Can Break It Down Into Lines:

1 | ==13422== 708 (16 direct, 692 indirect) bytes in...
Line one describes the type and amount of memory loss experienced.
2 | ==13422== at 0x4C2FB0F: malloc (in...
Line two describes the memory address and allocation function used to reserve the lost block.
3 | ==13422== by 0x108846: createLossyNode (valgrindMemoryLeaks.c:42)
Line three describes the memory address, function, source code file, and line number where the allocation occured.
4 and Beyond
Lines four and beyond are a stack trace.

Valgrind Does Not Know HOW The Program Lost The Memory, Only That The Memory Was Lost

Because Valgrind does not know where the memory was lost, it announces the only thing it does know, where the memory was allocated.

This is still useful information. By understanding what was lost, debugging can be narrowed to only follow the relevant data.

Using Input and Output Files (Redirection)

Master The < and > Symbols

< is called a left-chevron
> is called a right-chevron

< Means

[into this thing] < [read the contents of this file]

Example:
Windows: .\outputNameYouGaveToGCCEarlier.exe < .\inputFile.in
Linux: ./outputNameYouGaveToGCCEarlier.out < ./inputFile.in

> Means

[write the output from this] > [into this file]

Example:
Windows: .\outputNameYouGaveToGCCEarlier.exe > .\outputFile.txt
Linux: ./outputNameYouGaveToGCCEarlier.out > ./outputFile.txt

Note:
The output file will be created if it does not already exist.

Using Both

[Input To This File & Output From This File] < [from this file] > [into this file]

Example:
Windows: .\outputNameYouGaveToGCCEarlier.exe < .\inputFile.in > .\outputFile.txt
Linux: ./outputNameYouGaveToGCCEarlier.out < ./inputFile.in > ./outputFile.txt

That’s how it’s done. No, seriously, it’s that simple.

Yes, You Can Use Redirection Along With Other Commands

These sorts of things also work:
valgrind ./outputNameYouGaveToGCCEarlier.out < ./inputFile.in > ./outputFile.txt
time ./outputNameYouGaveToGCCEarlier.out < ./inputFile.in > ./outputFile.txt

Write Your Own Inputs

  • Open a text editor
  • Type the input you would normally type into the command line
    • Include the enters and don’t worry about the output at all
  • Save the file
  • You can use that as an input file with the < symbol
Don’t Want The Output?

In Linux you can dump unwanted output into the void using output redirection into /dev/null

Like This:
[command] > /dev/null

This will redirect the output of [command] into the void.

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