Integer overflow: Difference between revisions

Revision as of 21:37, 30 August 2022

Revision as of 22:47, 9 September 2022

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On 30 April 2015, the U.S. [[Federal Aviation Administration]] announced it will order [[Boeing 787]] operators to reset its electrical system periodically, to avoid an integer overflow which could lead to loss of electrical power and [[ram air turbine]] deployment, and Boeing deployed a [[software update]] in the fourth quarter.<ref>{{cite news |title= F.A.A. Orders Fix for Possible Power Loss in Boeing 787 |first=Jad |last=Mouawad |work=[[New York Times]] |date= 30 April 2015 |url= https://www.nytimes.com/2015/05/01/business/faa-orders-fix-for-possible-power-loss-in-boeing-787.html?_r=0}}</ref> The [[European Aviation Safety Agency]] followed on 4 May 2015.<ref>{{cite web |url= http://ad.easa.europa.eu/ad/US-2015-09-07 |work=Airworthiness Directives |title=US-2015-09-07: Electrical Power – Deactivation |date=4 May 2015 |publisher=[[European Aviation Safety Agency]]}}</ref> The error happens after 2³¹ hundredths of a second (about {{#expr:ceil(2^31/100/3600/24)}} days), indicating a 32-bit [[Signed number representations|signed]] [[Integer (computer science)|integer]].

Overflow bugs are evident in some computer games. In ''[[Super Mario Bros.]]'' for the [[NES]], the stored number of lives is a signed byte (ranging from −128 to 127) meaning the player can safely have 127 lives, but when the player reaches their 128th life, the counter rolls over to zero lives (although the number counter is glitched before this happens). This is caused by a data overflow, as the developers may not have thought said number of lives could be earned. In the arcade game ''[[Donkey Kong (video game)|Donkey Kong]]'', it is impossible to advance past level 22 due to an integer overflow in its time/bonus. The game calculates the time/bonus by taking the level number a user is on, multiplying it by 10, and adding 40. When they reach level 22, the time/bonus number is 260, which is too large for its 8-bit 256 value register, so it overflows to a value of 4 – too short to finish the level. In ''[[Donkey Kong Jr. Math]]'', when trying to calculate a number over 10,000, it shows only the first 4 digits. Overflow is the cause of the famous [[kill screen|"split-screen" level]] in ''[[Pac-Man]]''.<ref>{{cite web |url=http://home.comcast.net/~jpittman2/pacman/pacmandossier.html |title=The Pac-Man Dossier |last=Pittman |first=Jamey}}</ref> The notorious [[Nuclear Gandhi]] bug in [[Civilization (video game)|Civilization]] was purportedly caused by an integer underflow which occurred when the game attempted to subtract 2 from Gandhi's default aggression level of 1, setting it to 255, nearly 26 times higher than the normal maximum of 10. ([[Sid Meier]] claimed in an interview that this was, in fact, intentional.) Such a bug also caused the ''Far Lands'' in ''[[Minecraft]]'' which existed from the Infdev development period to Beta 1.7.3; it was later fixed in Beta 1.8 but still exists in ''Minecraft'' Pocket Edition and Windows 10 Edition.<ref>{{cite web |url=http://minecraft.gamepedia.com/Far_Lands |title=Minecraft Gamepedia Page |website=Minecraft Gamepedia}}</ref> In the [[Super Nintendo Entertainment System]] (SNES) game [[Lamborghini American Challenge]], the player can cause their amount of money to drop below $0 during a race by being fined over the limit of remaining money after paying the fee for a race, which glitches the integer and grants the player $65,535,000 more than it would have had after going negative.<ref>Archived at [https://ghostarchive.org/varchive/youtube/20211205/aNQdQPi0xMo Ghostarchive]{{cbignore}} and the [https://web.archive.org/web/20190726012137/https://www.youtube.com/watch?v=aNQdQPi0xMo&t=17m55s Wayback Machine]{{cbignore}}: {{cite web |url=https://www.youtube.com/watch?v=aNQdQPi0xMo&t=17m55s |title=Lamborghini American Challenge SPEEDRUN (13:24) |website=[[YouTube]]}}{{cbignore}}</ref> A similar glitch occurs in [[S.T.A.L.K.E.R.: Clear Sky]] where the player can drop into a negative amount by fast travelling without sufficient funds, then proceeding to the event where the player gets robbed and has all of their currency taken away. After the game attempts to take the player's money away to an amount of $0, the player is granted 2147482963 in game currency.<ref>{{Cite web |url=https://steamcommunity.com/app/20510/discussions/0/1484358860942756615/ |title=Money glitch :: S.T.A.L.K.E.R.: Clear Sky General Discussions}}</ref>

[[File:Error message due to an integer signedness bug in the stack setup code of MASM 1.00.gif|thumb|An integer signedness bug in the stack setup code emitted by the [[Pascal (programming language)|Pascal]] compiler prevented IBM–[[Microsoft Macro Assembler]] (MASM) version 1.00, a [[DOS]] program from 1981, and many other programs compiled with the same compiler, to run under some configurations with more than 512 KB of memory.]]