[sdcc-devel] [ sdcc-Bugs-477927 ] Un-inited variables in while loops

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Bugs item #477927, was opened at 2001-11-04 03:16
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Category: Live range problems
>Group: unreproducable
>Status: Closed
>Resolution: Out of Date
Priority: 5
Submitted By: Michael Hope (michaelh)
>Assigned to: Johan Knol (johanknol)
Summary: Un-inited variables in while loops

Initial Comment:
See the regression tests under this bug number.  Basically 
in:

int a;

do {
   b = fun();
   if (something on b) {
      a = ++array[b];
   }
} while (a != 123)

a is not initalised in all paths to the while conditional, but 
sdcc doesn't throw a warning.  What's really funky is that 
as 'a' is not inited before entering the while, 'a' only lives 
while in the do loop, and it can take on a random value 
depending on what other iTemps it shares registers with, 
causing the while condition to fail unpredictibly.

I don't know what the fix should be or if it should be fixed.


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>Comment By: Johan Knol (johanknol)
Date: 2003-03-26 13:18

Message:
Logged In: YES 
user_id=63512

This cannot be reproduced in latest cvs

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Comment By: Donald Delmar Davis (ddd7)
Date: 2002-05-26 17:58

Message:
Logged In: YES 
user_id=537284

I am finding that it doesnt bother to initialize ints in general.   
  
sdcc 2.3.0 for the 8051 takes this.  
------ snip   
TL1 = 0x88; TH1 = 0x88;  /* ~400 */  
 
/*  
 * Initialize variables for stepper movement  
 */  
rstg=0;       //unsigned int  
lstg=300;    //unsigned int  
rphase=0;   //unsigned char  
lphase=0;   //unsigned char  
------- endsnip  
And produces this  
------- snip  
;	stepper.c 100  
	mov	_TL1,#0x88  
	mov	_TH1,#0x88  
;	stepper.c 107  
	mov	_rphase,#0x00  
;	stepper.c 108  
	mov	_lphase,#0x00  
;	stepper.c 109  
---- endsnip   
  
I'D SAY THIS IS A PRETTY BIG BUG!!!  
....  
  

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