slice memory corruption on method call

[hundredwatt]

Zig Version

0.11.0-dev.251+7c527c6df

Steps to Reproduce and Observed Behavior

const std = @import("std");

fn unwrap(slice: []i32) i32 {
    // Commenting out this line fixes the output on Line 25:
    // std.debug.print("\n eval arg: {any}\n", .{slice[0]});
    return slice[0];
}

fn wrap(value: i32) []i32 {
    var arr: [1]i32 = undefined;
    arr[0] = value;

    // return arr[0..]; // same output
    return &arr;
}

pub fn main() void {
    var original: i32 = 255;
    var wrapped = wrap(original);

    std.debug.print("{}, {}\n", .{ original, wrapped[0] }); // prints '255, 255' as expected

    var unwrapped = unwrap(wrapped);

    std.debug.print("{}, {}\n", .{ original, unwrapped }); // prints '255, 3' unless Line 5 is commented out
}

$ zig run src/main.zig
255, 255
255, 3

Expected Behavior

A compiler error to prevent dangling pointer

[InKryption]

The result of wrap is a dangling pointer to arr. That is to say, after the function returns, arr is popped off the stack, and gets overwritten by other memory e.g. variables declared in later functions using the same stack. This is undefined behavior, not a bug.

[hundredwatt]

Should this have been prevented with a compiler error?

[InKryption]

There is ongoing discussion about that. There was a pull request adding such a compile error, but it wasn't merged as it is unclear how to write it into the spec for now.
Related: #5725, #11153

[hundredwatt]

Closing as dup of #5725. Thank you @InKryption