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Bug 958 - Timer Underflow
Summary: Timer Underflow
Status: RESOLVED INVALID
Alias: None
Product: SDL
Classification: Unclassified
Component: timer (show other bugs)
Version: HG 1.2
Hardware: All All
: P2 normal
Assignee: Ryan C. Gordon
QA Contact: Sam Lantinga
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2010-02-22 06:53 UTC by dino puller
Modified: 2010-02-24 01:15 UTC (History)
0 users

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Description dino puller 2010-02-22 06:53:55 UTC 
If you try to set a delay < 10ms a variable may got to underflow into 
void SDL_ThreadedTimerCheck(void)

I suggest to change:
		ms = t->interval - SDL_TIMESLICE;   
		next = t->next;
		if ( (int)(now - t->last_alarm) > (int)ms ) {

with:
		if ( (int)(now - t->last_alarm + SDL_TIMESLICE) > (int)ms ) {


bye,
   Dino
Comment 1 dino puller 2010-02-24 01:15:19 UTC 
(In reply to comment #0)
> If you try to set a delay < 10ms a variable may got to underflow into 
> void SDL_ThreadedTimerCheck(void)
> 
> I suggest to change:
>         ms = t->interval - SDL_TIMESLICE;   
>         next = t->next;
>         if ( (int)(now - t->last_alarm) > (int)ms ) {
> 
> with:
>         if ( (int)(now - t->last_alarm + SDL_TIMESLICE) > (int)ms ) {
> 
> 
> bye,
>    Dino


The suggested line was:
     if ( (int)(now - t->last_alarm + SDL_TIMESLICE) >  t->interval ) {

Anyway  t->interval is always rounded to be at least SDL_TIMESLICE, so no underflow will happen.