Re: Promoting unsigned long int to long int

pereges <Broli00@xxxxxxxxx> writes:
[...]
If I had to store 80-90 of structures and each had a member say
'axis'. How much of a difference would using a unsigned char over int
would make (for that member) ? For my program, space as well as
performance are important.

It depends.

If "axis" is the last member of your structure, it's likely that the
compiler will insert padding after it if it's an unsigned char anyway,
so declaring it as int would make no difference.

In the worst case (well, the worst plausible case), the cost of using
int would be 90 * (sizeof(int) - 1), which is trivial on anything
other than a small embedded system. But using int could easily save
code space, depending on the underlying architecture. And if you're
concerned about speed, it's likely (though by no means guaranteed)
that operations on int will be faster than operations on unsigned
char.

I think you're engaging in premature micro-optimization.

--
Keith Thompson (The_Other_Keith) kst-u@xxxxxxx <http://www.ghoti.net/~kst>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"
.

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