Pelles C forum
Pelles C => Bug reports => Topic started by: aj on August 27, 2008, 06:31:44 PM
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Using version 5.00.8 (Win64), on Vista SP1 x64 compiling a 64-bit DLL.
I've just spent 30 minutes looking for a bug in my program and what i found was this:
unsigned num;
num = 0;
for (i = 1; i <= some_maximum; i++) {
num++;
// other things happen here - not touching num
}
The error was that num was always set to one (1), no matter what - and it shouldn't.
The solution looked like this:
unsigned num;
num = 0;
for (i = 1; i <= some_maximum; i++) {
num = num + 1;
// other things happen here - not touching num
}Just that one line was changed, and my problem was solved.
I won't post more of the code here - but if Pelle is interested in this problem I can PM it to you.
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#include <stdio.h>
void main( void )
{
unsigned num;
int i;
num = 0;
for (i = 1; i <= 5; i++) {
printf("%d\n", num);
num++;
// other things happen here - not touching num
}
}
prints
0
1
2
3
4
What's the problem?
Robert Wishlaw
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The problem is that my code doesn't look like that.
It's a for-loop inside an if-case, all this in a function.
The solution I proposed earlier didn't solve the issue either. The reason it worked was a swprintf-call inserted in the for-loop, probably introducing a dependence that the compiler didn't think it could optimize away.
The real solution was an introduction of a variable 'temp' that just takes the value of 'num' and increases it and at a later point 'num = temp'.
I'm going to try to isolate the problem.
I know this info doesn't help very much, but as stated above the error occurs in code I'm not willing to post publicly - and I've got my hands full with other things right now.