Zig 0.16-dev Porting Notes

This skill captures gotchas hit when porting a 0.15 project to Zig 0.16-dev (std.Io world). APIs keep moving; always check the stdlib sources for your exact build.

Std.Io replaces std.net / legacy std.posix wrappers

```
std.net
```
is gone. The new networking lives under std.Io.net
(types:
```
IpAddress
```
,
```
Stream
```
,
```
Server
```
,
```
UnixAddress
```
, etc.).

High-level functions like

tcpConnectToHost

Address.parseIp

Stream.connect

Stream.read/writeAll

no longer exist. You must use

Io

vtables (

io.vtable.netConnectIp

netRead

netWrite

netListenIp

netAccept

If you need raw fds, call platform syscalls (
```
std.os.linux.socket
```
,
```
accept4
```
,
```
connect
```
,
```
bind
```
,
```
listen
```
,
```
write
```
,
```
writev
```
,
```
read
```
,
```
close
```
). Many helpers that were under
```
std.posix
```
are gone.

posix.socket

posix.bind

posix.accept

posix.shutdown

posix.writev

posix.listen

posix.pipe2

posix.getrandom

std.net.has_unix_sockets

, etc. are removed. Use

std.os.<platform>

syscalls and

posix.system.*

where available, or the Io vtable.

Epoll: use
```
std.os.linux.epoll_create1/epoll_ctl/epoll_wait
```
directly; signatures include an explicit
```
count
```
param for writev/epoll_wait.

Std.Io Readers/Writers

New writer/reader interfaces live under
```
std.Io
```
. TLS expects
```
*std.Io.Reader
```
/
```
*std.Io.Writer
```
(struct fields
```
.interface
```
). Pass pointers to interfaces, not call
```
interface()
```
as a function.

std.time.sleep

removed; use

std.Io.sleep(io, Duration, Clock)

Time / Random / Env / Exit

std.time.milliTimestamp

removed. Use

std.time.Timer

std.Io.Clock.now(clock, io)

and compare

Timestamp.nanoseconds

Random secure bytes:

std.Io.randomSecure(io, buf)

; no

std.crypto.random

std.posix.getrandom

convenience.

```
std.process.getEnvVarOwned
```
is gone; use
```
std.c.getenv
```
and copy.
```
std.posix.exit
```
removed; use
```
std.process.exit
```
.

TLS Client options

std.crypto.tls.Client.Options

now requires

entropy: *const [entropy_len]u8

and

realtime_now_seconds: i64

. Fill entropy with

std.Io.randomSecure

; compute seconds with

Io.Clock.now(.real, io)

ns_per_s

MemoryPool API changes

std.heap.MemoryPool(T).initCapacity(allocator, n)

returns the pool;

create

destroy

now require allocator. No bare

init()

or zero-arg

deinit()

Atomic order & Thread

Atomic orders use
```
.monotonic
```
/
```
.seq_cst
```
;
```
.awake
```
removed.

Format options

```
std.fmt.Options
```
replaces
```
FormatOptions
```
.
```
std.fmt.format
```
helper is gone; call
```
writer.print
```
directly (writers live in
```
std.Io.Writer
```
).

Randomness / crypto changes

std.crypto.random

was removed. Use an

std.Io

instance:

const io = std.Io.Threaded.global_single_threaded.ioBasic(); io.random(&buf);

Ed25519.KeyPair.generate

now requires an

io: std.Io

argument:

Ed25519.KeyPair.generate(io);

Enum conversion

std.meta.intToEnum

removed. Use

std.enums.fromInt(EnumType, value)

(returns

?EnumType

Fixed-buffer writers in tests

std.io.fixedBufferStream

was removed. For in-memory writes use

var w = std.Io.Writer.fixed(buf);

and read bytes with

std.Io.Writer.buffered(&w)

```
std.ArrayList
```
no longer has
```
.init(allocator)
```
shorthand; use
```
.initBuffer(slice)
```
for stack buffers or managed variants.

Stream/Conn helpers we added (compat pattern)

Build a thin compat layer that wraps platform syscalls to reintroduce
```
Stream { read, writeAll, close, readAtLeast }
```
and address parsing/formatting, plus
```
tcpConnectToHost/Address
```
using raw sockets.
For Unix sockets: build sockaddr manually and call
```
connect
```
.

Testing adjustments

For in-process client/server tests, use
```
socketpair(AF.UNIX, SOCK.STREAM|CLOEXEC, 0, &fds)
```
to avoid relying on Io vtable network (Threaded nets return
```
NetworkDown
```
if not wired).

Error sets tightened

Many functions return narrower error sets (e.g., Reader.fill no longer includes
```
WouldBlock
```
/
```
Timeout
```
). Remove unreachable branches accordingly.

syscalls return types

std.os.linux.*

return

usize

; cast with

@as(isize, @bitCast(rc))

before checking

< 0

. For

writev/epoll_wait

include the

count

argument.

Use this skill when upgrading 0.15-era code to 0.16-dev to avoid common build-breakers.

zig-0.16

NPX Install

Tags

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