Audit FreeBSD structs to match header files/ABI

[The-King-of-Toasters]

Required for #1759.

I wrote a simple project that verified the sizes against the headers at compile time:

const std = @import("std");
// Vendored from std/c/freebsd.zig.
// Change the first line to `@import("std");` to compile
const freebsd = @import("freebsd.zig");
const c = @cImport({
    @cInclude("sys/types.h");
    @cInclude("sys/socket.h");
    @cInclude("sys/event.h");
    @cInclude("sys/umtx.h");
    @cInclude("sys/link_elf.h");
    @cInclude("sys/fcntl.h");
    @cInclude("sys/stat.h");
    @cInclude("sys/timespec.h");
    @cInclude("sys/dirent.h");
    @cInclude("sys/socket.h");
    @cInclude("sys/signal.h");
    @cInclude("sys/ttycom.h");
    @cInclude("sys/ucontext.h");
    @cInclude("sys/stack.h");
    @cInclude("sys/poll.h");

    @cInclude("netinet/in.h");
    @cInclude("sys/un.h");
    @cInclude("netinet/if_ether.h");
    @cInclude("netdb.h");

    @cInclude("pthread.h");
    @cInclude("semaphore.h");
});

fn assertType(comptime ZigType: anytype, comptime CType: anytype) void {
    std.debug.assert(@sizeOf(ZigType) == @sizeOf(CType));
    std.debug.assert(@bitSizeOf(ZigType) == @bitSizeOf(CType));
    std.debug.assert(@alignOf(ZigType) == @alignOf(CType));
}

fn assert(comptime T: []const u8) void {
    return assertType(@field(freebsd, T), @field(c, T));
}

comptime {
    assert("sf_hdtr");
    assert("pthread_mutex_t");
    assert("pthread_cond_t");
    assert("pthread_rwlock_t");
    assert("pthread_attr_t");
    assert("sem_t");
    assert("_umtx_time");
    assertType(freebsd.Kevent, c.struct_kevent);
    assert("dl_phdr_info");
    assertType(freebsd.Flock, c.struct_flock);
    assert("msghdr");
    assertType(freebsd.Stat, c.struct_stat);
    assert("timespec");
    assert("timeval");
    assert("dirent");
    assert("sockaddr");
    assertType(freebsd.sockaddr.in, c.sockaddr_in);
    assertType(freebsd.sockaddr.in6, c.sockaddr_in6);
    assertType(freebsd.sockaddr.un, c.sockaddr_un);
    assert("sigval");
    assert("sigset_t");
    assert("winsize");
    assertType(freebsd.Sigaction, c.struct_sigaction);
    assert("siginfo_t");
    assert("mcontext_t");
    assert("ucontext_t");
    assert("stack_t");
    assert("addrinfo");
    assert("pollfd");
    //     @compileError(std.fmt.comptimePrint("{d} {d}\n", .{
    //         @sizeOf(freebsd.mcontext_t),
    //         @sizeOf(c.mcontext_t),
    //     }));
}

This was ran on a FreeBSD 13.1-RELEASE amd64 system using zig version 0.10.0-dev.2842+d65e248ed.

I added some doc-comments from the headers where I could. Also included is the mcontext_t definition for aarch64 systems when that gets supported down the line.

[The-King-of-Toasters]

I had to change the event loop code to deal with a change in Kevent.udata's type. Would appreciate the feedback from the owner.

EDIT: I'm backing this out, as all Kevent targets have the same issue. This should be dealt with in a followup pr for all of them.

[ifreund]

Nice work, this is a cool way to catch some errors.

Note that it only works for the target run on though, for example FreeBSD's stat structure seems to have extra fields when targeting i386: https://github.com/freebsd/freebsd-src/blob/d80d73493767111b7569e831a93061014c682274/sys/sys/stat.h#L170

I didn't have time to review everything in depth, but here's a start

[The-King-of-Toasters]

Updating this PR to audit the kinfo_file structure that was added in #12082. I've also backed out the arm mcontext bits, as I couldn't actually get zig to compile on an aarch64 vm. I'll leave that for #3939.

[andrewrk]

Thank you and nice work!