regression: compiling a x86-windows app with threads with a 64-bit compiler

[llogick]

Zig Version

0.12.0-dev.3634+3d1652070

Steps to Reproduce and Observed Behavior

> zig build -freference-trace --summary all -Dtarget=x86-windows
install
└─ install zls
   └─ zig build-exe zls Debug x86-windows 2 errors
/home/rad/lab/zig/build/stage4/lib/zig/std/Thread/Pool.zig:92:39: error: @fieldParentPtr increases pointer alignment
            const closure: *@This() = @fieldParentPtr("run_node", run_node);
                                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/rad/lab/zig/build/stage4/lib/zig/std/Thread/Pool.zig:92:39: note: '*align(4) Thread.Pool.spawn__anon_10636.Closure' has alignment '4'
/home/rad/lab/zig/build/stage4/lib/zig/std/Thread/Pool.zig:92:39: note: '*Thread.Pool.spawn__anon_10636.Closure' has alignment '8'
/home/rad/lab/zig/build/stage4/lib/zig/std/Thread/Pool.zig:92:39: note: use @alignCast to assert pointer alignment
referenced by:
    spawn__anon_10636.Closure: /home/rad/lab/zig/build/stage4/lib/zig/std/Thread/Pool.zig:88:58
    runFn: /home/rad/lab/zig/build/stage4/lib/zig/std/Thread/Pool.zig:92:29
/home/rad/lab/zig/build/stage4/lib/zig/std/Thread/Pool.zig:92:39: error: @fieldParentPtr increases pointer alignment
            const closure: *@This() = @fieldParentPtr("run_node", run_node);
                                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/rad/lab/zig/build/stage4/lib/zig/std/Thread/Pool.zig:92:39: note: '*align(4) Thread.Pool.spawn__anon_10640.Closure' has alignment '4'
/home/rad/lab/zig/build/stage4/lib/zig/std/Thread/Pool.zig:92:39: note: '*Thread.Pool.spawn__anon_10640.Closure' has alignment '8'
/home/rad/lab/zig/build/stage4/lib/zig/std/Thread/Pool.zig:92:39: note: use @alignCast to assert pointer alignment
referenced by:
    spawn__anon_10640.Closure: /home/rad/lab/zig/build/stage4/lib/zig/std/Thread/Pool.zig:88:58
    runFn: /home/rad/lab/zig/build/stage4/lib/zig/std/Thread/Pool.zig:92:29
error: the following command failed with 2 compilation errors:
/home/rad/lab/zig/build/stage4/bin/zig build-exe -freference-trace=256 -ODebug -target x86-windows -mcpu baseline --dep exe_options --dep tracy --dep known-folders --dep zls -Mroot=/home/rad/lab/zls/npdm/src/main.zig -Mexe_options=/home/rad/lab/zls/npdm/zig-cache/c/cdb97d55e32f50fc9169d1029ec866c5/options.zig -ODebug -target x86-windows -mcpu baseline --dep options -Mtracy=/home/rad/lab/zls/npdm/src/tracy.zig -Mknown-folders=/home/rad/.cache/zig/p/12201314cffeb40c5e4e3da166217d2c74628c74486414aaf97422bcd2279915b9fd/known-folders.zig --dep known-folders --dep diffz --dep tracy --dep build_options --dep version_data -Mzls=/home/rad/lab/zls/npdm/src/zls.zig -Moptions=/home/rad/lab/zls/npdm/zig-cache/c/afa1e7d8563bc1d60b4c78e42a5d2105/options.zig -Mdiffz=/home/rad/.cache/zig/p/12200d71e4b7029ea56a429e24260c6c0e85a3069b0d4ba85eace21a0fd75910aa64/DiffMatchPatch.zig -Mbuild_options=/home/rad/lab/zls/npdm/zig-cache/c/657d1a35550280ee156902394a1ec894/options.zig -Mversion_data=/home/rad/lab/zls/npdm/zig-cache/o/e184a1362fefa6803c3727e5faace999/version_data_master_19824.zig --cache-dir /home/rad/lab/zls/npdm/zig-cache --global-cache-dir /home/rad/.cache/zig --name zls --listen=- 

Expected Behavior

It used to work afaik.

[rohlem]

If the pointer logic is sound (which it presumably is), the code now needs to assert the required alignment via @alignCast.
(EDIT: Meaning we forgot to update std in this place.)

[Vexu]

This was an intentional change in #19470

[nektro]

those errors and notes are all in the standard library.

my confusion is how is a *Thread.Pool.spawn__anon_10636.Closure have an alignment of 8 on 32bit ?

[Techatrix]

Here is a code snippet that triggers the compile error:

const std = @import("std");

fn getOptional() ?u64 {
    return 0;
}

fn func(_: u64) void {}

pub fn main() !void {
    var thread_pool: std.Thread.Pool = undefined;
    thread_pool.init(.{ .allocator = std.heap.page_allocator });
    defer thread_pool.deinit();

    if (getOptional()) |value| {
        try thread_pool.spawn(func, .{value});
    }
}

This doesn't happen if value is just const value: u64 = 0;