processExecutableOpen

fn processExecutableOpen(userdata: ?*anyopaque, flags: Dir.OpenFileOptions) process.OpenExecutableError!File {
    const t: *Threaded = @ptrCast(@alignCast(userdata));
    switch (native_os) {
        .wasi => return error.OperationUnsupported,
        .linux, .serenity => return dirOpenFilePosix(t, .{ .handle = posix.AT.FDCWD }, "/proc/self/exe", flags),
        .windows => {
            // If ImagePathName is a symlink, then it will contain the path of the symlink,
            // not the path that the symlink points to. However, because we are opening
            // the file, we can let the openFileW call follow the symlink for us.
            const image_path_name = windows.peb().ProcessParameters.ImagePathName.sliceZ();
            const prefixed_path_w = try wToPrefixedFileW(null, image_path_name, .{});
            return dirOpenFileWtf16(null, prefixed_path_w.span(), flags);
        },
        .driverkit,
        .ios,
        .maccatalyst,
        .macos,
        .tvos,
        .visionos,
        .watchos,
        => {
            // _NSGetExecutablePath() returns a path that might be a symlink to
            // the executable. Here it does not matter since we open it.
            var symlink_path_buf: [posix.PATH_MAX + 1]u8 = undefined;
            var n: u32 = symlink_path_buf.len;
            const rc = std.c._NSGetExecutablePath(&symlink_path_buf, &n);
            if (rc != 0) return error.NameTooLong;
            const symlink_path = std.mem.sliceTo(&symlink_path_buf, 0);
            return dirOpenFilePosix(t, .cwd(), symlink_path, flags);
        },
        else => {
            var buffer: [Dir.max_path_bytes]u8 = undefined;
            const n = try processExecutablePath(t, &buffer);
            buffer[n] = 0;
            const executable_path = buffer[0..n :0];
            return dirOpenFilePosix(t, .cwd(), executable_path, flags);
        },
    }
}