LLVM assertion in ChildProcess.spawnPosix

[mproved]

const std = @import("std");

pub const io_mode = .evented;

pub fn main() !void {
    var gpa = std.heap.GeneralPurposeAllocator(.{}){};

    var array = &[_][]const u8{ "java", "-Xmx2G", "-jar", "server.jar", "nogui" };

    var child_process = try std.ChildProcess.init(array, &gpa.allocator);
    child_process.cwd = "auth";
    child_process.stdin_behavior = std.ChildProcess.StdIo.Pipe;
    child_process.stdout_behavior = std.ChildProcess.StdIo.Pipe;
    child_process.stderr_behavior = std.ChildProcess.StdIo.Pipe;

    var process_frame = async child_process.spawnAndWait();

    // std.time.sleep(1_000_000_000 * 40);

    _ = try child_process.stdin.?.write("stop\n");

    // var term_status = await process_frame;

    // std.debug.print("{}", .{term_status});
}

broken LLVM module found: Basic Block in function 'std.child_process.ChildProcess.spawnPosix' does not have terminator! label %OkResume
Instruction does not dominate all uses!
  %28 = load { %std.child_process.Term, i16 }*, { %std.child_process.Term, i16 }** %6, align 8, !dbg !23024
  %41 = bitcast { %std.child_process.Term, i16 }* %28 to i8*, !dbg !23024

This is a bug in the Zig compiler.
Unable to dump stack trace: debug info stripped
Aborted (core dumped)

[elerch]

I ran across a similar issue and in my reduction narrowed it down to working with std.ChildProcess under evented io. Commenting line 4 (pub const io_mode = .evented) in the code below will compile successfully. Compiling as is will produce the error on versions 0.6.0 -> current master 31802c6

const std = @import("std");
const allocator = std.heap.page_allocator;

pub const io_mode = .evented;

pub fn main() !void {
    const process = try std.ChildProcess.init(&[_][]const u8{ "zig", "version" }, allocator);
    defer process.deinit();
    try process.spawn();
}

[17dec]

This appears to be the result of #5728. forkChildErrReport() is marked as noreturn but uses async calling convention in evented io_mode due to writeIntFd()'s use of File.write().

Workaround is to add a 'nosuspend' before the last line in writeIntFd().

[chr1sniessl]

I'm currently trying to use the workaround for spawnPosix by adding nosuspend, however I'm still seeing a similar issue on my machine:

broken LLVM module found: Instruction does not dominate all uses!
%28 = load { %std.child_process.Term, i16 }, { %std.child_process.Term, i16 }** %6, align 4, !dbg !80716
%41 = bitcast { %std.child_process.Term, i16 } %28 to i8*, !dbg !80716

This is a bug in the Zig compiler.thread 2209 panic:
Unable to dump stack trace: debug info stripped

My implementation of the workaround is:

fn writeIntFd(fd: i32, value: ErrInt) !void {
    const file = File{
        .handle = fd,
        .capable_io_mode = .blocking,
        .intended_io_mode = .blocking,
    };
    nosuspend file.writer().writeIntNative(u64, @intcast(u64, value)) catch return error.SystemResources;
}

This is using zig-bootstrap to generate the zig binary for aarch64-linux-musl cortex_a72.