Calculating with a variable outside of its bounds in C
- by aquanar
If I make a calculation with a variable where an intermediate part of the calculation goes higher then the bounds of that variable type, is there any hazard that some platforms may not like?
This is an example of what I'm asking:
int a, b;
a=30000;
b=(a*32000)/32767;
I have compiled this, and it does give the correct answer of 29297 (well, within truncating error, anyway). But the part that worries me is that 30,000*32,000 = 960,000,000, which is a 30-bit number, and thus cannot be stored in a 16-bit int. The end result is well within the bounds of an int, but I was expecting that whatever working part of memory would have the same size allocated as the largest source variables did, so an overflow error would occur.
This is just a small example to show my problem, I am trying to avoid using floating points by making the fraction be a fraction of the max amount able to be stored in that variable (in this case, a signed integer, so 32767 on the positive side), because the embedded system I'm using I believe does not have an FPU.
So how do most processors handle calculations out of the bounds of the source and destination variables?
