The Last Line Effect

The Last Line Effect

Moritz Beller@Inventitech

Andy Zaidman

Andrey Karpov

https://twitter.com/Inventitech

TrinityCore ExampleLast Line Effect



Chromium ExampleLast Statement Effect





Chromium Example

Chromium Example

Chromium Example

Chromium Example

Chromium Example

Chromium Example

Chromium Example

Clone Class

Chromium Example

Clone Class

AST-Node1

Chromium Example

Clone Class

AST-Node

1

1

Chromium Example

Clone Class

AST-Node

1 2

1

Chromium Example

Clone Class

AST-Node

1 2 3

1

Chromium Example

Clone Class

AST-Node

1 2 3 4

1

Chromium Example

Clone Class

AST-Node

1 2 3 4 5

1

Chromium Example

Clone Class

AST-Node

1 2 3 4 5

1

Chromium Example

Clone Class

AST-Node

1 2 3 4 5

1

Type 2 Clone: “syntactically identical cop[ies]; only variable, type, or function identifiers have […] changed.” Koschke, 2007.

Chromium Example

Clone Class

AST-Node

1 2 3 4 5

1

Type 2 Clone: “syntactically identical cop[ies]; only variable, type, or function identifiers have […] changed.” Koschke, 2007.

Very Short Type 2-Clone: Micro-Clone

Very Short Clones: Micro-Clones

Shortcut: Identical Subexpressions






Shortcut to Faulty Micro-Clones

PVS-Studio

PVS-Studio

208 OSS projectsPVS-Studio




202 Faulty Micro-Clones


202 Faulty Micro-Clones

Error Distribution for Micro-Clones> 1 Line

Error Distribution for Micro-ClonesWithin 1 Line

What We Do Not Know (Yet) ...

● Why did we find so few faulty micro-clones?








● Are faulty micro-clones common among micro-clones?










● How are micro-clones created and evolved?




● How are micro-clones created and evolved?

@InventitechMoritz Beller, TU Delft


https://twitter.com/Inventitech







> code.|

Software

The Last Line Effect