std.mem.sort deleting parts of array; Zig 0.11

[lusty mica]

Can you share your code?

[desert lotus]

fn cmp(_: void, a: []const u8, b: []const u8) bool {
    return std.mem.order(u8, a, b) == .lt;
} 

pub fn main() !void {
    var files: [][]const u8 = undefined;

    var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
    defer arena.deinit();

    var allocator = arena.allocator();
    files = try get_files(allocator, dir);        
    defer allocator.free(files);

    std.debug.print("{s}\n", .{files}); // All there

    std.mem.sort([]const u8, files, {}, cmp);

    std.debug.print("{s}\n", .{files}); // Some randomly removed
}```

[lusty mica]

Hmm, that's weird

[fierce tulip]

What does get_files look like? I can't come up with any other problem than that it allocates the array on the stack

Although it also feels unlikely since you pass an allocator to it

[desert lotus]

    var files = std.ArrayList([]const u8).init(allocator);

    var iter = (try std.fs.cwd().openIterableDir(dir, std.fs.Dir.OpenDirOptions {
        .access_sub_paths = false,
        .no_follow = true,
    })).iterate();

    while (try iter.next()) |entry| {
        try files.append(entry.name);    
    }

    return files.toOwnedSlice();
}

[wind ether]

you have to duplicate the names, they don't last past next

[desert lotus]

but why do some only some of them get deleted

[wind ether]

who cares, you are accessing invalid memory, it could contain anything even old strings

[desert lotus]

but when I print it out the first time they're all there. then they only disappear when I call sort

{ .local, .dbus, .vimrc, .w3m, .cache, .cargo, .xinitrc, .Xauthority, .zshrc, .surf, .inputrc, code, .vim, .config, .lesshst, .ssh }

{ �, .inputrc, hst, .ssh, .surf,
                                 , , , , , .Xauthority, .cache, .cargo, .vimrc, .w3m, .xini }

[wind ether]

calling any function at all whatsoever potentially clobbers this invalid memory in random ways

[fierce tulip]

The stack is not actually destroyed when you leave a scope, it's just not preserved and can be overwritten by future operations

So the names that you have on the stack are not overwritten by the print function, probably because it's considerably smaller stack-wise than your get_files