Objectives of this webinar How we detected error patterns Patterns themselves and how to avoid them: 3.1 Copy-paste and last line effect 3.2 if (A) {...} else if (A) 3.3 Errors in checks 3.4 Array index out of bounds 3.5 Operator precedence 3.6 Typos that are hard to spot How to use static analysis properly Conclusion Q&A

1. Typical errors in code on the example of
C++, C#, and Java
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2. Георгий Грибков
About the speaker
Information Technology Video Developer Network http://itvdn.com
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C++ developer of the PVS-Studio static code analyzer
• Develops the analyzer core, new diagnostics, supports users.
• Introduced PVS-Studio in the godbolt.org online compiler.
• Wrote articles for the Habr website and gave talks at IT conferences,
related to searching for bugs in code.
Typical errors in code on the example of C++, C#, and Java

3. Agenda
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1. Objectives of this webinar
2. How we detected error patterns
3. Patterns themselves and how to avoid them:
3.1 Copy-paste and last line effect
3.2 if (A) {...} else if (A)
3.3 Errors in checks
3.4 Array index out of bounds
3.5 Operator precedence
3.6 Typos that are hard to spot
4. How to use static analysis properly
5. Conclusion
6. Q&A
Заключение
Typical errors in code on the example of C++, C#, and Java

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Typical errors in code on the example of C++, C#, and Java

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Typical errors in code on the example of C++, C#, and Java

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Typical errors in code on the example of C++, C#, and Java

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Typical errors in code on the example of C++, C#, and Java

11. Information Technology Video Developer Network http://itvdn.com
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Typical errors in code on the example of C++, C#, and Java

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Typical errors in code on the example of C++, C#, and Java

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Typical errors in code on the example of C++, C#, and Java

14. Information Technology Video Developer Network http://itvdn.com
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Typical errors in code on the example of C++, C#, and Java

15. Information Technology Video Developer Network http://itvdn.com
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Typical errors in code on the example of C++, C#, and Java

16. Information Technology Video Developer Network http://itvdn.com
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Typical errors in code on the example of C++, C#, and Java

17. Information Technology Video Developer Network http://itvdn.com
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Typical errors in code on the example of C++, C#, and Java

18. Information Technology Video Developer Network http://itvdn.com
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*
Typical errors in code on the example of C++, C#, and Java

19. Information Technology Video Developer Network http://itvdn.com
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BUGS ARE EVERYWHERE!
Typical errors in code on the example of C++, C#, and Java

20. How to avoid errors
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• Warn developers of typical problems
• Use tools to automatically search for errors
Typical errors in code on the example of C++, C#, and Java

21. Objectives of this webinar
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• Demonstrate typical error patterns in code
• Show how to use static analysis properly
Typical errors in code on the example of C++, C#, and Java

22. 2. How we detected error patterns
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Typical errors in code on the example of C++, C#, and Java

23. What is static analysis
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Static analysis is automated code review.
Typical errors in code on the example of C++, C#, and Java

24. What is static analysis
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Typical errors in code on the example of C++, C#, and Java

25. Examples of static analyzers
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• PVS-Studio
• Cppcheck
• Infer
• IntelliJ IDEA
• Clang Static Analyzer
• FindBugs
• ...
Long list of static analyzers:
Typical errors in code on the example of C++, C#, and Java

26. How we detected error patterns
Information Technology Video Developer Network http://itvdn.com
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Typical errors in code on the example of C++, C#, and Java
Found errors
380 13747
Checked
projects
Detected
errors

27. Check out the base of errors we found:
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Typical errors in code on the example of C++, C#, and Java

28. 3. Patterns themselves and how to avoid them
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Typical errors in code on the example of C++, C#, and Java

29. Pattern № 1:
Copy-paste and last line effect
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Typical errors in code on the example of C++, C#, and Java

30. Elasticsearch (Java)
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Typical errors in code on the example of C++, C#, and Java

31. Elasticsearch (Java)
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PVS-Studio warning:
V6039 There are two 'if' statements with identical
conditional expressions. The first 'if' statement
contains method return. This means that the
second 'if' statement is senseless.
Typical errors in code on the example of C++, C#, and Java

32. Information Technology Video Developer Network http://itvdn.com
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Clang (C++)
Typical errors in code on the example of C++, C#, and Java

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Clang (C++)
PVS-Studio warning: V501 There are identical sub-expressions
SM.getExpansionColumnNumber(ContainerREnd)' to the left and to the right of the '>=' operator.
Typical errors in code on the example of C++, C#, and Java

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Clang (C++)
PVS-Studio warning: V501 There are identical sub-expressions
SM.getExpansionColumnNumber(ContainerREnd)' to the left and to the right of the '>=' operator.
Typical errors in code on the example of C++, C#, and Java

35. Xenko Game Engine (C#)
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Typical errors in code on the example of C++, C#, and Java

36. Xenko Game Engine (C#)
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PVS-Studio warning: V3001 There are
identical sub-expressions 'box.Maximum.X
- box.Minimum.X > sphere.Radius' to the
left and to the right of the '&&' operator.
Typical errors in code on the example of C++, C#, and Java

37. Pattern № 1: Copy-paste and last line effect
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• We selected 84 examples of erroneous code
written with copy-paste
• 43 of them had an error in the last line!
• It is more than 50%!
Typical errors in code on the example of C++, C#, and Java

38. Information Technology Video Developer Network http://itvdn.com
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• Stop copy-pasting
• Copy-pasting in programming is pure evil!
• If you dare to – be extremely attentive
How to avoid
Typical errors in code on the example of C++, C#, and Java

39. Pattern № 2.
if (A) {...} else if (A)
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Typical errors in code on the example of C++, C#, and Java

40. Elasticsearch (Java)
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Typical errors in code on the example of C++, C#, and Java

41. Elasticsearch (Java)
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PVS-Studio warning:
V6003 The use of 'if (A) {....} else if (A)
{....}' pattern was detected. There is a
probability of logical error presence.
Typical errors in code on the example of C++, C#, and Java

42. Chromium (C++)
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Typical errors in code on the example of C++, C#, and Java

43. Chromium (C++)
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PVS-Studio warning:
V517 The use of 'if (A) {...} else if (A)
{...}' pattern was detected. There is a
probability of logical error presence.
Check lines: 61, 63.
Typical errors in code on the example of C++, C#, and Java

44. CryEngine V (C++)
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Typical errors in code on the example of C++, C#, and Java

45. CryEngine V (C++)
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PVS-Studio warning:
V517 The use of 'if (A) {...} else if (A)
{...}' pattern was detected. There is a
probability of logical error presence.
Check lines: 266, 268.
Typical errors in code on the example of C++, C#, and Java

46. CryEngine V (C++)
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PVS-Studio warning:
V517 The use of 'if (A) {...} else if (A)
{...}' pattern was detected. There is a
probability of logical error presence.
Check lines: 266, 268.
Typical errors in code on the example of C++, C#, and Java

47. MonoDevelop (C#)
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Typical errors in code on the example of C++, C#, and Java

48. MonoDevelop (C#)
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Typical errors in code on the example of C++, C#, and Java

49. MonoDevelop (C#)
Information Technology Video Developer Network http://itvdn.com
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Typical errors in code on the example of C++, C#, and Java

50. MonoDevelop (C#)
Information Technology Video Developer Network http://itvdn.com
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Typical errors in code on the example of C++, C#, and Java

51. MonoDevelop (C#)
Information Technology Video Developer Network http://itvdn.com
ITVDN
Typical errors in code on the example of C++, C#, and Java

52. MonoDevelop (C#)
Information Technology Video Developer Network http://itvdn.com
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PVS-Studio warning:
V3021 There are two 'if' statements
with identical conditional
expressions. The first 'if' statement
contains method return. This means
that the second 'if' statement is
senseless.
Typical errors in code on the example of C++, C#, and Java

53. Information Technology Video Developer Network http://itvdn.com
ITVDN
• Try to do best not to copy-paste
• If you’re still going to copy-paste, copy non-compiled constructions.
• Example:
if (value == _)
return _;
How to avoid?
Typical errors in code on the example of C++, C#, and Java

54. Pattern № 3.
Errors in checks
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Typical errors in code on the example of C++, C#, and Java

55. Unity (C#)
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Typical errors in code on the example of C++, C#, and Java

56. Unity (C#)
Information Technology Video Developer Network http://itvdn.com
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PVS-Studio warning:
V3063 A part of conditional
expression is always true if it is
evaluated: pageSize <= 1000.
Typical errors in code on the example of C++, C#, and Java

57. Bullet - the engine of Red Dead Redemption (C++)
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Typical errors in code on the example of C++, C#, and Java

58. Bullet - the engine of Red Dead Redemption (C++)
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PVS-Studio warning:
V709 Suspicious comparison found:
'f0 == f1 == m_fractureBodies.size()’.
Remember that
'a == b == c’
is not equal to
'a == b && b == c'.
Typical errors in code on the example of C++, C#, and Java

59. Apache Hive (Java)
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Typical errors in code on the example of C++, C#, and Java

60. Apache Hive (Java)
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PVS-Studio warning: V6030 The method located to the right of the '|' operator will be called regardless of
the value of the left operand. Perhaps, it is better to use '||'.
Typical errors in code on the example of C++, C#, and Java

61. Chromium (C++)
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Typical errors in code on the example of C++, C#, and Java

62. Chromium (C++)
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Typical errors in code on the example of C++, C#, and Java

63. Chromium (C++)
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PVS-Studio warnings:
 V547 Expression
'time.month <=
kDaysInMonth[time.month] + 1' is
always true.
 V547 Expression
'time.month <=
kDaysInMonth[time.month]’
is always true.
Typical errors in code on the example of C++, C#, and Java

64. Information Technology Video Developer Network http://itvdn.com
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• «Pay attention!» won’t work every time 
• Try backup tools
How to avoid
Typical errors in code on the example of C++, C#, and Java

65. Pattern № 4.
Array index out of bounds
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Typical errors in code on the example of C++, C#, and Java

66. Stickies (C++)
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Typical errors in code on the example of C++, C#, and Java

67. Stickies (C++)
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PVS-Studio warning:
V557 Array overrun is possible. The
'64' index is pointing beyond array
bound. stickies stickies.cpp
Typical errors in code on the example of C++, C#, and Java

68. Elasticsearch (Java)
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Typical errors in code on the example of C++, C#, and Java

69. Elasticsearch (Java)
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PVS-Studio warning: V6025 Possibly index '(int) x' is out of bounds.
Typical errors in code on the example of C++, C#, and Java

70. Elasticsearch (Java)
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PVS-Studio warning: V6025 Possibly index '(int) x' is out of bounds.
Typical errors in code on the example of C++, C#, and Java

71. IPP Samples (C++)
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Typical errors in code on the example of C++, C#, and Java

72. IPP Samples (C++)
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Typical errors in code on the example of C++, C#, and Java

73. IPP Samples (C++)
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Typical errors in code on the example of C++, C#, and Java

74. IPP Samples (C++)
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Typical errors in code on the example of C++, C#, and Java

75. IPP Samples (C++)
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PVS-Studio warning:
V557 Array overrun is possible. The '30'
index is pointing beyond array bound.
Typical errors in code on the example of C++, C#, and Java

76. FastReport (C#)
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Typical errors in code on the example of C++, C#, and Java

77. FastReport (C#)
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PVS-Studio warning:
V3106 Possible negative index value. The value
of 'idx' index could reach -1.
Typical errors in code on the example of C++, C#, and Java

78. Information Technology Video Developer Network http://itvdn.com
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• Be careful when you add '0’ to the end of the string
• Do you get an external index? Make sure you check it!
• Don’t mix up '>' ('<‘) and '>=' ('<=‘) when comparing the index with the array size
How to avoid
Typical errors in code on the example of C++, C#, and Java

79. 4. How to use static analysis properly
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Typical errors in code on the example of C++, C#, and Java

80. When you should perform static analysis
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Typical errors in code on the example of C++, C#, and Java

81. When you should perform static analysis
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Static analysis
Typical errors in code on the example of C++, C#, and Java

82. How to make the most of static analysis
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• Apply static analysis at early stages
• Analyze regularly
Typical errors in code on the example of C++, C#, and Java

83. Proprietary development
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Typical errors in code on the example of C++, C#, and Java

84. Proprietary development
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Typical errors in code on the example of C++, C#, and Java

85. Proprietary development
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Typical errors in code on the example of C++, C#, and Java

86. Proprietary development
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Typical errors in code on the example of C++, C#, and Java

87. Proprietary development
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Typical errors in code on the example of C++, C#, and Java

88. Corporate development
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Typical errors in code on the example of C++, C#, and Java

89. Corporate development
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Typical errors in code on the example of C++, C#, and Java

90. Corporate development
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Typical errors in code on the example of C++, C#, and Java

91. Corporate development
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Typical errors in code on the example of C++, C#, and Java

92. Corporate development
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Typical errors in code on the example of C++, C#, and Java

93. Corporate development
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Typical errors in code on the example of C++, C#, and Java

94. Corporate development
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Typical errors in code on the example of C++, C#, and Java

95. Open-source development
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Typical errors in code on the example of C++, C#, and Java

96. Open-source development
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Typical errors in code on the example of C++, C#, and Java

97. Open-source development
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ITVDN
Typical errors in code on the example of C++, C#, and Java

98. Open-source development
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Typical errors in code on the example of C++, C#, and Java

99. More about analysis of commits and pull-requests
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Typical errors in code on the example of C++, C#, and Java

100. 5. Conclusion
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Typical errors in code on the example of C++, C#, and Java

101. Typical error patterns in code
Information Technology Video Developer Network http://itvdn.com
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• Copy-paste and last line effect
• if (A) {...} else if (A)
• Errors in checks
• Array index out of bounds
• … (the list gradually expands)
Typical errors in code on the example of C++, C#, and Java

102. How to avoid typical errors
Information Technology Video Developer Network http://itvdn.com
ITVDN
• Stop copy-pasting!
• Seriously, stop copy-pasting!
• Pay attention to checks, even small and short ones.
• Carefully check array indexes.
• Regularly use static analysis.
Typical errors in code on the example of C++, C#, and Java

103. Free PVS-Studio license for students
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ITVDN
https://bit.ly/pvs-student
Typical errors in code on the example of C++, C#, and Java

104. Information Technology Video Developer Network http://itvdn.com
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Q&A
Typical errors in code on the example of C++, C#, and Java

105. Information Technology Video Developer Network http://itvdn.com
ITVDN
Watch our video lessons on C++
At ITVDN you’ll find a collection of video courses and webinars for C++ developers.
Go to ITVDN.com and watch our video lessons right now!

106. IT VIDEO DEVELOPERS NETWORK
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