Re: An example of MACHO programming and why is wrong

jacob navia wrote:

.... snip ...

Suppose:
struct S {
unsigned n;
double d;
double data[8192];
};

I want to allocate 65520 objects of size 65 552 bytes each.

If you do that in a 32 bit system what you obtain?
i=65520, i*sizeof(*p)=4,294,967,040 as signed number = -256

WE OBTAIN A NEGATIVE NUMBER.

Very simple. We detect the 'unsigned overflow' by:

if (((n = a * b) < a || (n < b)) overflow()
else alliswell(n);

--
Merry Christmas, Happy Hanukah, Happy New Year
Joyeux Noel, Bonne Annee.
Chuck F (cbfalconer at maineline dot net)
<http://cbfalconer.home.att.net>


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