Java-Gaming.org    
Featured games (79)
games approved by the League of Dukes
Games in Showcase (475)
Games in Android Showcase (106)
games submitted by our members
Games in WIP (530)
games currently in development
News: Read the Java Gaming Resources, or peek at the official Java tutorials
 
    Home     Help   Search   Login   Register   
Pages: [1]
  ignore  |  Print  
  Java & integer Overflow  (Read 979 times)
0 Members and 1 Guest are viewing this topic.
Offline Abuse

JGO Coder


Medals: 11


falling into the abyss of reality


« Posted 2007-03-26 20:29:05 »

Does anybody ever wish Java detected & reported integer overflow (via some kind of ArithmeticException) ?

For there to be no compile time, or runtime checking for this fail-slow error seems to me to be a serious limitation in the construction of complex systems.
The simplest assumption that many people fall foul of :-
1  
assert Math.abs(val)>=0;

The above assertion will fail when val = Integer.MIN_VALUE (as it will overflow round to itself)

A very common application of this flawed assertion would be :-

1  
Math.abs(random.nextInt())%range

Which will lead to an erroneous value being generated every 1 in ~4294967296 executions.
While the above is poor code (in both J2ME & J2SE), I have seen many examples of its usage.

Another common situation where overflow becomes a brain melter is when using FixedPoint libraries  Embarrassed

Make Elite IV:Dangerous happen! Pledge your backing at KICKSTARTER here! https://dl.dropbox.com/u/54785909/EliteIVsmaller.png
Offline t_larkworthy

Senior Member


Medals: 1
Projects: 1


Google App Engine Rocks!


« Reply #1 - Posted 2007-03-26 21:04:18 »

If all my code failed one in 4294967296 times, I would be a happy and probably rich man.

Runesketch: an Online CCG built on Google App Engine where players draw their cards and trade. Fight, draw or trade yourself to success.
Offline Riven
« League of Dukes »

JGO Overlord


Medals: 742
Projects: 4
Exp: 16 years


Hand over your head.


« Reply #2 - Posted 2007-03-26 21:15:47 »

PITA, but if you want to be sure....

1  
2  
3  
4  
5  
         int a = ...;
         int b = ...;
         int c = a * b;

         assert ( ((a >>> 31) ^ (b >>> 31)) == (c >>> 31) );



Eh... which works... for 'quite a few' cases Smiley (damn double int overflow)

Hi, appreciate more people! Σ ♥ = ¾
Learn how to award medals... and work your way up the social rankings
Pages: [1]
  ignore  |  Print  
 
 
You cannot reply to this message, because it is very, very old.

 

Add your game by posting it in the WIP section,
or publish it in Showcase.

The first screenshot will be displayed as a thumbnail.

ctomni231 (34 views)
2014-07-18 06:55:21

Zero Volt (30 views)
2014-07-17 23:47:54

danieldean (25 views)
2014-07-17 23:41:23

MustardPeter (27 views)
2014-07-16 23:30:00

Cero (42 views)
2014-07-16 00:42:17

Riven (44 views)
2014-07-14 18:02:53

OpenGLShaders (33 views)
2014-07-14 16:23:47

Riven (34 views)
2014-07-14 11:51:35

quew8 (30 views)
2014-07-13 13:57:52

SHC (66 views)
2014-07-12 17:50:04
HotSpot Options
by dleskov
2014-07-08 03:59:08

Java and Game Development Tutorials
by SwordsMiner
2014-06-14 00:58:24

Java and Game Development Tutorials
by SwordsMiner
2014-06-14 00:47:22

How do I start Java Game Development?
by ra4king
2014-05-17 11:13:37

HotSpot Options
by Roquen
2014-05-15 09:59:54

HotSpot Options
by Roquen
2014-05-06 15:03:10

Escape Analysis
by Roquen
2014-04-29 22:16:43

Experimental Toys
by Roquen
2014-04-28 13:24:22
java-gaming.org is not responsible for the content posted by its members, including references to external websites, and other references that may or may not have a relation with our primarily gaming and game production oriented community. inquiries and complaints can be sent via email to the info‑account of the company managing the website of java‑gaming.org
Powered by MySQL Powered by PHP Powered by SMF 1.1.18 | SMF © 2013, Simple Machines | Managed by Enhanced Four Valid XHTML 1.0! Valid CSS!