Cousot_MIT_2005_Course_02_4-1

Cousot_MIT_2005_Course_02_4-1 - Software verication Patrick...

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« Software verification » Patrick Cousot Jerome C. Hunsaker Visiting Professor Massachusetts Institute of Technology Department of Aeronautics and Astronautics cousot mit edu www.mit.edu/ ~ cousot Course 16.399: “Abstract interpretation” http://web.mit.edu/afs/athena.mit.edu/course/16/16.399/www/ Course 16.399: “Abstract interpretation”, Tuesday, February 15, 2005 1 ľ P. Cousot , 2005 The Long-Standing Software Safety and Security Problem § x Course 16.399: “Abstract interpretation”, Tuesday, February 15, 2005 2 ľ P. Cousot , 2005 What is (or should be) the essential preoccupation of computer scientists? The production of reliable software, its mainte- nance and safe evolution year after year (up to 20 even 30 years). Course 16.399: “Abstract interpretation”, Tuesday, February 15, 2005 3 ľ P. Cousot , 2005 Computer hardware change of scale The 25 last years, computer hardware has seen its per- formances multiplied by 10 4 to 10 6 = 10 9 ; ENIAC (5000 flops) Intel/Sandia Teraflops System (10 12 flops) Course 16.399: “Abstract interpretation”, Tuesday, February 15, 2005 4 ľ P. Cousot , 2005
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The information processing revolution A scale of 10 6 is typical of a significant revolution : - Energy : nuclear power station / Roman slave; - Transportation : distance Earth — Mars / Boston — Washington Course 16.399: “Abstract interpretation”, Tuesday, February 15, 2005 5 ľ P. Cousot , 2005 Computer software change of scale The size of the programs executed by these computers has grown up in similar proportions ; Example 1 (modern text editor for the general public): - > 1 700 000 lines of C 1 ; - 20 000 procedures; - 400 files; - > 15 years of development. 1 full-time reading of the code (35 hours/week) would take at least 3 months! Course 16.399: “Abstract interpretation”, Tuesday, February 15, 2005 5 ľ P. Cousot , 2005 Computer software change of scale (cont’d) Example 2 (professional computer system): - 30 000 000 lines of code; - 30 000 (known) bugs ! Course 16.399: “Abstract interpretation”, Tuesday, February 15, 2005 6 ľ P. Cousot , 2005 Bugs Software bugs - whether anticipated (Y2K bug) - or unforeseen (failure of the 5.01 flight of Ariane V launcher) are quite frequent ; – Bugs can be very difficult to discover in huge software; Bugs can have catastrophic consequences either very costly or inadmissible (embedded software in transportation sys- tems); Course 16.399: “Abstract interpretation”, Tuesday, February 15, 2005 7 ľ P. Cousot , 2005
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The estimated cost of an overflow 500 000 000 $ ; – Including indirect costs (delays, lost markets, etc): 2 000 000 000 $; – The financial results of Arianespace were negative in 2000, for the first time since 20 years. Course 16.399: “Abstract interpretation”, Tuesday, February 15, 2005 8 ľ P. Cousot , 2005 Who cares? No one is legally responsible for bugs : This software is distributed WITHOUT ANY WARRANTY; without even the implied war- ranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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