On Tuesday, 23 January 2024 at 17:54:25 UTC, bachmeier wrote:
On Tuesday, 23 January 2024 at 12:34:38 UTC, Nick Treleaven
wrote:
But I'm strongly in favour of catching any bugs at
compile-time (and have been since before I discovered D). I
just object to anyone trying to downgrade the importance of
automated memory-safety checking.
I'm not downgrading the importance of memory safety. All I'm
saying is that you can't sell D as a safe language if has bugs
like this.
Here's a reduced version of one of the most bizarre bugs I've
dealt with in any language. The only reason I didn't move on to
another language was because I was too busy at the time.
The code allows for initial values if the index is less than 0,
otherwise it returns the element.
```
import std;
double value(T)(T index, double * x) {
if (index - 5 < 0) {
return 0.0;
} else {
return x[index-5];
}
}
void main() {
double[] v = [1.1, 2.2, 3.3];
// Works
writeln(value(3, v.ptr));
// Lucky: program segfaults
writeln(value(v.length, v.ptr));
}
```
I noticed this behavior only because the program crashes. Once
I figured out what was going on, I realized that the thousands
of lines of code I had already written needed to be checked and
possibly rewritten. If only I had a compiler to do that for me.
This code seems to be doing everything it can to run into
undefined behaviour, though?
Why is `index` of a type T that has no requirements at all (when
the implementation quite clearly wants `size_t`, or at least an
unsigned numerical value)? Why is it using a pointer for x when
clearly you intend to use it as a slice? You probably have
context that I don't, but I would never expect this sort of code
to be anywhere near @safe :D
