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GMNG 4312 –Game Engines

Unit 02:Tools of the Trade

Alireza Tavakkoli, Ph.D.

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Objectives

Tools of the Trade Version Control Visual Studio 2010 Profiling Tools Memory Leaks and Corruption Detection Tools Other Tools

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Version Control

What is Version Control? Multiple users to work on a project

Trace changes Keep track of multiple modifications Share the latest code Avoid unintentional code corruptions

Even for one user Keep a copy of the latest files on the repository

On multiple machines! Version control keeps track of the history of the

files! Also called source control.

Can be used to keep track of text files and binaries as well.

Invaluable in Gaming Industry! 3

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Why Using Version Control?

Reasons to use version control Central repository Keeping history of changes Tagging specific code versions for retrieval Branching off from main development for patches

and updates

As mentioned source control is also useful in single engineer projects!

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Common Version Control Systems SCCS and RCS

Source Code Control System and Revision Control System Oldest version control systems Use command line interface

CVS Concurrent Version System

Heavy-duty professional grade version control Command-line based Mostly in UNIX bases systems CVSSNT (WinCVS) is the windows counterpart

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Common Version Control Systems

Subversion Open source version control system Popular for individual, student, small studio

projects We use this!

Git Open source revision control

Used for linux kernel Make changes to files Commit to branches Git can roll the diff(erences) and reapply them to

new bases revisions rebasing.

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Common Version Control Systems

Perforce A Professional grade source control system Change lists:

A collection of source files that have been modified as a logical unit.

Useful as a transaction processing unit Either all changes within the list are submitted or

none will.

NxN Alienbrain A source control system for the game industry Support very large databases

Specially for binary assets like movies, 3D models, etc.

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Common Version Control Systems

ClearCase Very large scale software production

A Unique UI that extends the windows explorer functionality

Expensive!

Microsoft Visual SourceSafe Light-weight source control package

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Subversion and TortoiseSVN We use Subversion

It’s free It’s nice and reliable Easy to setup

Actually we use GoogleCode! A number of windows and mac subversion clients

We use TortoiseSVN Client-Server Architecture

Server contains the repository Client connect to server to update the repository

Commits, Updates, Tags, Revisions, Branches, etc.

Let’s see how to set up our Source Version Control system.

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Setting Up Version Control

Code.Google.Com http://code.google.com

Setup an account Sign in Go to project hosting Create a project for Google Code (or Eclipse Labs).

Set up administrative options and users. 4GB with 200MB upload size limit

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Setting Up Version Control

Download and install TortoiseSVN: http://tortoisesvn.tigris.org Using TortoiseSVN

Create folders in your local machine Right-click and from context menu

Check out project Use “https://” URL for checkout with commit

functionality Uset “http://” URL for read-only checkouts

URLs can be found under your “profile” after signing-in to GoogleCode

To commit you need GoogleCode password Differenet than your google account password

Go to project source GoogleCode password

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Using SVN

File Versions, Updating, Committing Multiple programmer – Multiple files

Keep track of changes Use a master version of all files

This is your repository!

All versions will remain in the repository! Even deletes You can track every thing in the repository Even commits that “break” the build!

Each programmer has a local copy After updating with repository Work on your local copy

Commit the changes you made when you are absolutely certain you would want to do so!

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Using SVN

Diffs During a commit operation a diff is created

Changes between the repository and local version Line by line comparison Double click in the commit dialog to see the diffs

Can check it out on google code as well.

Non Versioned files New files that don’t exist in the repository

Missing The files that are deleted Will not be removed from repository!

Are tagged as deleted.

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Using SVN

Multiple Check Outs Exclusive checkout

Locking items that are checked out Ensure no simultaneous edits!

Subversion does not explicitly asks this! Multiple checkouts The first committed files become the latest on the

repository! Other commits must be merged with the latest version! More than one set of diffs is generated!

Most conflicts can be resolved automatically Editing different parts by different users!

In other cases a three-way merge is necessary

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Using SVN

Three-way Merge When programmers made changes to similar

contents

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Version 1

checkout (A)

Version 1

checkout (A) Version 2

Version 1

Checkout (A) Version 2

Version 3

checkout (B)

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Using SVN

Deleting Files Deleted files are not really gone! They are merely tagged as deleted.

The users will no longer see files in their local directory.

Use “Show Log” to see and access the deleted files.

Un-deleting the files Recommit the latest version

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Microsoft Visual Studio

There are many compilers for C++ What is a compiler How are C++ files used?

Compile + Link

MS Visual Studio Professional Express

http://www.microsoft.com/express/download

Visual Studio is an IDE Source code + Machine code + debugger

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Different Files

Source, header and translation units Source code contains the course files. C++, C,

CPP, etc. Translation Units

Compiler translates into machine code Header files

Contain type declaration, function prototypes, etc. Share between translation units Compiler doesn’t see header files

Preprocessor! Use #include statement Distinct from programmer’s point of view!

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Libraries, Executables, DLLs Object File

The translated version of a translation unit (.obj or .O) Relocatable

Code memory addresses not determined. Unilked

External references (to functions, etc.) have not been resolved.

Libraries Groups of object files! A convenience

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Libraries, Executables, DLLs Executables

Objects and libraries have to be “linked” into executable files.

Contain fully resolved machine code

Linkers operations To calculate final relative addresses of all machine

code Ensure all external references are resolved properly

Global data Reference functions

Executable is relocateable The addresses are still relative to the base address

It is finalized when the executable is in RAM!

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Dynamic Linked Library (DLL) What is a DLL?

Hybrid between (static) library and executable Acts like a library

Contains functions that can be called Acts like an executable

Can be loaded by the OS independently Contains startup and shutdown code!

Executables that use DLLs contain partially linked machine code The references and data to the DLL remain

unlinked! Upon running the OS resolves the unlinked

information from the DLL. Load the DLLs in the memory and patch in the

addresses! Look for them in the bin folder .

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Projects and Solutions

Projects Collection of source files that compile into

Executables, libraries or DLLs Stored in .vcproj Are XML files

Human readable

Solutions are the collections of Projects

Solution Explorer Solution is the root

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Build Configurations

Variety of Options in MSVS Command line C:\> cl /c function.cpp /Fo Function.obj /Wall /Od /Zi

Compile all warnings on no optimization generate debugging information

This is too complicated and impractical Use build configurations

What is a build configuration A collection of options for preprocessor, compiler,

linker, etc. Can make different configurations for different

translation units. Two most important configurations

Debug and Release

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Common Build Options

Preprocessor Settings Handles

the header expansions Type definitions

Can define preprocessor macros Macros act like code! Are replaced in code! Very Efficient!

Example _DEBUG

#ifdef _DEBUG Some debug lines

#endif

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Compiler Settings

Controlling debugging information Makes executable file larger

Runs less efficiently Can walk through your code and see values Can reverse-engineer a project

Inline function Expansion For optimization

How does it work? Off Once in memory Why is it useful? Is inlining good?

Speed vs. Debugging

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Compiler Settings (Continued) Optimizations

E.G. Inline Expansion Reorder statements Variable manipulations Less debuggability

In debug mode Turn off all optimizations

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Linker Settings

Linker is what makes the external references resolve. Define type of output files

Executable or DLL Which external libraries to link

Paths to find them Common practice

Link debug libraries with debug builds and release with release builds Debug libraries are less optimized

Controlling things like stack size, etc.

See MSVS 2010 Express

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Typical Build Settings

Debug Slow version Good for debugging

Additional information, less optimization

Release Faster version Debugging and assertions still on

Production Final game files

Tools Used for conditionally build shared code to use by

other tools Ex. Expose code that’s not used by the game, and use

#ifdef _TOOLS_BUILD directive.

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Build Configurations and Testability

The more build configuration the more difficult the testing Usually testing not done in debug Some builds may show up some bugs that are not

in other builds Test betas and alpha!

Advantage Keep build configurations to a minimum

Ship release build after thorough tests!

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Project Configuration

Project properties General Debugging C++ Linker

Configuration dropdown combo box

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Project Configuration

The General Tab

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Project Configuration

The General Tab Macros

Benefits Can relocate

See a complete list

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Project Configuration

The Debugging Tab

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Project Configuration

The C/C++ Tab

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Project Configuration

The C/C++ Tab

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Project Configuration

The Linker Tab

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Project Configuration

The Linker Tab

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Creating A New C++ Project Setup and Empty Project

OGRE Make the modifications and configurations settings

Use A Wizard

Copy A Working Project May need to make modifications to the

CML .vcproj file $(OutDIr)\MyGame.exe $(OutDir)\(ProjectName).exe

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Debugging Your Code

The startup project Breakpoints Stepping through your code The call stack The watch window Data breakpoints Conditional breakpoints

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The Startup Project

A Solution may contain more than one project Only one project can be debugged at a time

The Startup Project Setting

The Startup Project Bold face in the solution explorer

“F5” debugs the startup executable!

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Break Points

Invaluable for debugging Stop the execution of the project for you to see all

sorts of things. “F9” toggles a break point in code

To step through your code F10

Single-step-over F11

Single-step-in

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The Call Stack

Shows the stack (and order) of functions

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The Watch Window

Inspect variable values

Type any expression Call functions Define suffixes

,d ,x ,n

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Data Break Points

Trigger whenever a memory address is changed Also called hardware breakpoints.

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Conditional Breakpoint

Evaluate a condition and if true stop for debugging E.g. have 20 tanks but want to see the values of

the 4th one! Call conditional on the value of a class!

Or when running a loop you want to see what happens after 400 iterations Press F5 400 times! Or set up a hit count

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Debugging optimization builds

Learn disassembly Use registers to deduce variables Inspect variables and object contents by

address Use static and global variables Modify the code

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Profiling Tools

Most of the time is spend by the least part of the code!

Statistical Profilers Use CPU information for percentage of function

CPU use Instrumenting Profilers

Comprehensive profiling data At the expense of the execution time!

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Memory Leaks and Corruption Detection

What’s great about C++ Pointers

What can be the source of evil in C++ Pointers

Allocation/deallocation inconsistency Dangling pointers Memory leaks

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Other Tools

Difference tools

Three way merge tools

Hex Editors

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Questions?

Game Engine Architecture Chapter 2

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