Hi,

import std.stdio;

void main() {
	int[3] arr;
	writeln(arr);
	arr = new int[5];
	writeln(arr);
}


$ dmd static_array.d
$ ./static_array
[0, 0, 0]
core.exception.RangeError@static_array.d(6): Range violation
----------------
??:? _d_arrayboundsp [0x55e4830afcb5]
??:? _Dmain [0x55e48308f957]


$ ldc2 static_array.d
$ ./static_array
[0, 0, 0]
Illegal instruction (core dumped)

Why this code can be compiled and causing runtime error? it should be caught at compile time!

On Friday, 14 October 2022 at 18:57:44 UTC, mw wrote:

import std.stdio;

void main() {
    int[3] arr;
    writeln(arr.ptr);
    arr = new int[3];
    writeln(arr.ptr);
    writeln(typeid(arr));
}

output (e.g.):

7FFD5EBF1530
7FFD5EBF1530
int[3]

It's not a reassignment of arr, but a copying of the contents of the dynamic array, and it crashes with an oversized array as the lengths don't match, same as if you did

    int[] other = new int[5];
    foreach (i; 0 .. other.length)
        arr[i] = other[i];

On Saturday, 15 October 2022 at 10:31:16 UTC, matheus wrote:

It would be better to error on assigning a new array expression to a static array, there's no reason to allow that. A static array can be assigned a single element arr = 0 instead. Although ideally there would be some syntactical way of making it clear when assigning a slice to a static array, perhaps requiring [] at the end unless it is already a SliceExpression or an array literal. Then the syntax would tell you if the right hand side had a compile-time known length not (and hence you can rely on a compile-time error if lengths don't match).

On Friday, 14 October 2022 at 20:19:20 UTC, Ali Çehreli wrote:

 arr = new int[5];

I recently updated the docs to prefer the new E[](length) form instead:

https://dlang.org/spec/expression.html#NewExpression

At some point the T[length] form should be deprecated. Perhaps we could have a compiler switch -strict that deprecates a set of things, e.g. struct postblit. This would be used for anything which needs a long deprecation period and to avoid annoying people by adding new deprecations spread out over a number of releases. Instead they can update their code using the -strict check once in a while.

On Friday, 14 October 2022 at 18:57:44 UTC, mw wrote:

Looks like an LDC bug.

On Saturday, 15 October 2022 at 11:29:00 UTC, rassoc wrote:

It printed the arrays

[0, 0, 0]
[0, 0, 0]

... lol did it cache the results of the previous call? Somebody please explain this, is this what Timon meant by undefined behaviour getting introduced in programs whose asserts get removed from the code?