"bearophile" wrote in message news:[email protected]...
From my experience in coding in D they are far more unlikely than
sign-related bugs of array lengths.
Here's a simple program to calculate the relative size of two files, that
will not work correctly with unsigned lengths.
module sizediff
import std.file;
import std.stdio;
void main(string[] args)
{
assert(args.length == 3, "Usage: sizediff file1 file2");
auto l1 = args[1].read().length;
auto l2 = args[2].read().length;
writeln("Difference: ", l1 - l2);
}
The two ways this can fail (that I want to highlight) are:
1. If either file is too large to fit in a size_t the result will (probably)
be wrong
2. If file2 is bigger than file1 the result will be wrong
If length was signed, problem 2 would not exist, and problem 1 would be more
likely to occur. I think it's clear that signed lengths would work for more
possible realistic inputs.
While this is just an example, a similar pattern occurs in real code
whenever array/range lengths are subtracted.
