How to Avoid Bugs? Educate developers about common bugs. Use tools to look for bugs automatically.

1. Game Engine Code Quality:
Is Everything Really That Bad?

2. About Me:
George Gribkov
A C++ developer and developer of the PVS-
Studio static code analyzer.
I write articles on finding bugs in games
(Vangers, VVVVVV) and other open-source
projects.
gribkov@viva64.com
2

3. Unreal Engine 4
3

4. Unreal Engine 4
4

5. Assassins Creed: Unity
5

6. The Witcher 3: Wild Hunt
6

7. The Sims
7

8. BUGS EVERYWHERE
=))))))))))))))
8

9.  Educate developers about common bugs
 Use tools to look for bugs automatically
How to Avoid Bugs?
9

10.  Show typical error patterns
 Show how to use static code analysis
correctly
This Talk Aims To:
10

11. What Errors in Game Engines Look Like
11

12. Copy-Pasting and
the Last Line Effect
12

13. Unreal Engine 4 (C++)
13

14. PVS-Studio warns: V501 There are identical sub-expressions
'Position.Y >= Control.Center.Y — BoxSize.Y * 0.5f' to the left and to
the right of the '&&' operator.
Unreal Engine 4 (C++)
14

15. Using an Invalid
Address
15

16. Amazon Lumberyard (C++)
16

17. PVS-Studio warns: V557 CWE-119 Array overrun is possible.
The 'id' index is pointing beyond array bound.
Amazon Lumberyard (C++)
17

18. Unreal Engine 4
18

19. Unreal Engine 4
19
PVS-Studio warns: V522
Dereferencing of the
null pointer
'LevelStreamingObject'
might take place.

20. Evil Thrives in
Conditional
Expressions
20

21. Unity (C#)
21

22. PVS-Studio warns: V3063 A part of conditional expression is
always true if it is evaluated: pageSize <= 1000.
Unity (C#)
22

23. Bullet – Red Dead Redemption’s Engine (C++)
23

24. PVS-Studio warns:
V709 Suspicious
comparison found:
'f0 == f1 ==
m_fractureBodies.size()’.
Remember that
'a == b == c’
is not equal to
'a == b && b == c'.
Bullet –Red Dead Redemption’s Engine (C++)
24

25. Operator
Precedence
25

26. CryEngine (C++)
26

27. PVS-Studio warns: V502 Perhaps the '?:' operator works in a
different way than it was expected. The '?:' operator has a lower
priority than the '+' operator.
CryEngine (C++)
27

28. Amazon Lumberyard (C++)
28

29. PVS-Studio warns: V502 Perhaps the '?:' operator works in a
different way than it was expected. The '?:' operator has a
lower priority than the '-' operator.
Amazon Lumberyard (C++)
29

30. And Oh-So Many
Elusive Typos…
30

31. CryEngine V (C++)
31

32. PVS-Studio warns: V529 Odd semicolon ';' after 'for' operator.
CryEngine V (C++)
32

33. Amazon Lumberyard
33

34. PVS-Studio warns: V549 CWE-688 The first argument of
'memcmp' function is equal to the second argument.
Amazon Lumberyard
34

35. And Here’s What We Get
35

36. 36

37. What to Do
37

38. Do Trust the Engines
38
 All these errors are already fixed
 Developers actively work on preventing new
ones

39. Fight Bugs
39

40.  Unit tests
 Code review
 Functional, regression testing
Fight Bugs
40

41.  Unit tests
 Code review
 Functional, regression testing
 Dynamic analysis
 Static analysis
Fight Bugs
41

42.  Unit tests
 Code review
 Functional, regression testing
 Dynamic analysis
 Static analysis
Fight Bugs
42

43. Static analysis – is an automatic code
review procedure.
What Is Static Analysis?
43

44. What Is Static Analysis?
44

45. Static Analysis Advantages
45

46. id Software
Wargaming
Epic Games
Playrix
Warner Brothers
Who Uses Static Analysis…
46
Oculus
Codemasters
Rocksteady
ZeniMax Media
And others…

47. Modern Static Analyzers
47
• PVS-Studio
• ReSharper
• Coverity
• SonarQube
• Klocwork
• Clang Static Analyzer
• IntelliJ IDEA
• ...
• A details list of static
analyzers:

48. Analysis: How and Where
48

49.  Locally on developers’ computers (plugins for IDE,
compilation monitoring systems)
Analysis: How and Where
49

50.  In continuous integration systems (command-line tools,
plugins for CI systems, monitoring systems)
Analysis: How and Where
50

51. A Typical Scenario
51

52. A Typical Scenario
52

53. A Typical Scenario
53

54. A Typical Scenario
54

55. Классический сценарий
55

56. A Typical Scenario
56

57. A Typical Scenario
57

58. A Typical Scenario
58

59.  Errors are fixed the moment they appear
 Many errors are fixed before testing and do not
get to that stage
 Those that made it are detected at night
Recap
59

60. Static Analysis Advantages
60

61.  Errors are fixed the moment they appear
 Many errors are fixed before testing and do not
get to that stage
 Those that made it are detected at night
 The cost to fix bugs is almost zero
Recap
61

62.  Of course! Static analysis does not find all bugs
 Static analysis – is an answer to the "how else can I improve code
quality?" question
 An example of a great combination: static + dynamic analysis
Should You Use Other Approaches?
62

63. Conclusion
63

64.  Everyone makes mistakes. Even experts.
 This is normal, you can use special tools to
fix them.
Conclusion
64

65. Typical error patterns:
 Copy-pasting and the last line effect
 Using an incorrect address
 Errors in conditional operators
 Operation precedence issues
 Elusive typos
Conclusion
65

66.  You can save a lot of resources, if you set up
continuous static analysis
Conclusion
66

67. 67
Use this QR code to get a one-
month PVS-Studio free trial

68. 68
Use this QR code to get a one-
month PVS-Studio free trial
Q&A