changing pointers

[emekoi]

in my code i pass a pointer to a struct to one of it's method but the pointer's address differs from the address of the actual struct by 20. the address of the actual struct also differs from the address of the struct i return in the initializer by 4 as well. the code in question is here. running the code on windows will produce 3 different values for the address of the window. an anyone tell me why the pointers are all different?

[winksaville]

Supplying an a code sample of the failure would be helpful.

…

On Sat, Oct 27, 2018 at 8:40 PM emekoi ***@***.***> wrote: in my code i pass a pointer to a struct to one of it's method but the pointer's address differs from the address of the actual struct by 20. the address of the actual struct also differs from the address of the struct i return in the initializer by 4 as well. can anyone tell me why my pointers are all different? — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#1688>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AA-hHMm2xjsVad8yHumi82t61gR89fgKks5upScXgaJpZM4X9w8a> .

[emekoi]

here's an example that's just produces different random pointer values:

const std = @import("std");

pub fn main() void {
    const opts = Window.Options.{ .title = "hello_world" };
    var window = Window.init(opts);
    std.debug.warn("main: {}\n", @ptrToInt(&window));
    window.info();
}

pub const Window = struct.{
    const Self = @This();

    pub const Options = struct.{ title: []const u8 };

    title: []const u8,

    pub fn init(options: Options) Self {
        var result = Self.{ .title = options.title };
        std.debug.warn("init: {}\n", @ptrToInt(&result));
        return result;
    }

    pub fn info(self: *Self) void {
        std.debug.warn("info: {}\n", @ptrToInt(&self));
    }

};

[tgschultz]

    pub fn init(options: Options) Self {
        var result = Self.{ .title = options.title };
        std.debug.warn("init: {}\n", @ptrToInt(&result));
        return result;
    }

copy elision isn't in yet (see #287, #1682), so the result created in this function body is copied on return.

    pub fn info(self: *Self) void {
        std.debug.warn("info: {}\n", @ptrToInt(&self));
    }

self is a pointer, so &self is a pointer to a pointer. @ptrToInt(self) should be correct (that is, it should match main:).

pub fn main() void {
    const opts = Window.Options.{ .title = "hello_world" };
    var window = Window.init(opts);
    std.debug.warn("main: {}\n", @ptrToInt(&window));
    window.info();
}

window is the instance that was copied from result created in Window.init.

[emekoi]

thanks! this was really messing me up.