Audit use std.posix

[lalinsky]

In zig 0.16, std.posix is going to be removed, only posix.system and some exceptions remain.

[lalinsky]

@claude Check what we use in the current code. Make an audit and replace steps in logical groups.

[claude]

Claude finished @lalinsky's task in 31m 20s —— View job • claude/issue-345-20260313-1032 • [Create PR ➔](https://github.com/lalinsky/zio/compare/main...claude/issue-345-20260313-1032?quick_pull=1&title=Issue%20%23345%3A%20Changes%20from%20Claude&body=This%20PR%20addresses%20issue%20%23345%0A%0AGenerated%20with%20%5BClaude%20Code%5D(https%3A%2F%2Fclaude.ai%2Fcode)

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Audit and Replacement Complete

All std.posix.* usages have been removed from the codebase. Here's a summary of the changes grouped by concern:

Changes Made

19 files changed, 190 insertions, 109 deletions

src/os/posix.zig — Central abstraction layer (major additions)

• Added pub const fd_t = sys.fd_t;
• Added close() wrapper function
• Added signal handling: Sigaction, SIG, SA, siginfo_t, sigset_t, sigemptyset(), sigaction(), raise() — wrappers handle both pre-0.16 (c_int) and 0.16+ (enum) signal types via anytype parameters
• Fixed sigaction() to cast to u8 on Linux (where std.os.linux.sigaction takes u8)

src/os/system/linux.zig + src/os/system/c.zig — Type additions

• Added ino_t and pid_t exports

src/os/net.zig — New socket wrappers

• Added setsockopt() and getsockopt() wrappers using posix.system.*

Signal handling — src/coro/stack.zig + src/signal.zig

• All std.posix.Sigaction, std.posix.SIG.*, std.posix.SA.*, std.posix.sigaction(), std.posix.raise() → posix.*
• std.posix.abort() → std.process.abort()
• Simplified invokePreviousHandler to use unified posix.sigaction()/posix.raise() wrappers

Other files

• src/net.zig: std.posix.setsockopt/getsockopt → os.net.setsockopt/getsockopt
• src/os/base.zig: std.posix.iovec/iovec_const → std.c.iovec/iovec_const
• src/os/fs.zig: std.posix.fd_t/mode_t/ino_t/DT.* → local/posix.sys.*/posix.system.*; STDIN/STDOUT/STDERR → integer literals
• src/os/thread.zig: std.posix.E/errno() → posix.sys.E/posix.errno()
• src/os/linux.zig, src/os/netbsd.zig, src/os/openbsd.zig: std.posix.timespec → posix.timespec/std.c.timespec
• src/dns/posix.zig, src/dns/darwin.zig: std.posix.SOCK.*/IPPROTO.* → os_net.*
• src/dns/root.zig: Removed redundant || std.posix.UnexpectedError
• src/ev/backends/epoll.zig, src/ev/completion.zig: std.posix.fd_t/pid_t → posix.fd_t/posix.sys.pid_t
• test_runner.zig: std.posix.exit() → std.process.exit()

Test Results

All 382 unit tests pass. Examples and benchmarks build successfully.

Branch

claude/issue-345-20260313-1032 — ready for PR creation.