golang.org/x/sys v0.31.0: unix.Close

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify golang.org/x/sys/unix.Close in pkg:golang/golang.org/x/sys@v0.31.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/sys@v0.31.0
Demonstrate these symbols/APIs:
  - golang.org/x/sys/unix.Close

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:25fbee1a8b756720d237382597fb3a6b7eebc7826b9b59598e393d42de716082","contract":["unix.Close successfully closes valid file descriptors without error","unix.Close returns EBADF when closing an invalid file descriptor","unix.Close returns EBADF when attempting to close an already-closed file descriptor","unix.Close on the write end of a pipe causes read on the read end to receive EOF"],"goal":"verify golang.org/x/sys/unix.Close in pkg:golang/golang.org/x/sys@v0.31.0","kind":"HOW","packages":["pkg:golang/golang.org/x/sys@v0.31.0"],"schemaVersion":1,"symbols":["golang.org/x/sys/unix.Close"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/golang.org/x/sys@v0.31.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/sys@v0.31.0","symbols":["golang.org/x/sys/unix.Close"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.23.0

require golang.org/x/sys v0.31.0

golang.org/x/sys v0.31.0 h1:ioabZlmFYtWhL+TRYpcnNlLwhyxaM9kWTDEmfnprqik=
golang.org/x/sys v0.31.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=

package main

import (
	"fmt"
	"os"

	"golang.org/x/sys/unix"
)

// SafeClose closes a file descriptor using unix.Close and wraps any error.
func SafeClose(fd int) error {
	if err := unix.Close(fd); err != nil {
		return fmt.Errorf("close fd %d failed: %w", fd, err)
	}
	return nil
}

// CreateAndClosePipe creates a pipe and immediately closes both descriptors.
func CreateAndClosePipe() error {
	var fds [2]int
	if err := unix.Pipe(fds[:]); err != nil {
		return fmt.Errorf("pipe failed: %w", err)
	}
	if err := SafeClose(fds[0]); err != nil {
		_ = unix.Close(fds[1])
		return err
	}
	if err := SafeClose(fds[1]); err != nil {
		return err
	}
	return nil
}

func main() {
	if err := CreateAndClosePipe(); err != nil {
		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
		os.Exit(1)
	}
	fmt.Println("Successfully created and closed pipe file descriptors")
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/sys/unix.Close in pkg:golang/golang.org/x/sys@v0.31.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/sys@v0.31.0"
  ],
  "symbols": [
    "golang.org/x/sys/unix.Close"
  ]
}

package main

import (
	"errors"
	"fmt"
	"os"

	"golang.org/x/sys/unix"
)

func main() {
	// Assertion 1: unix.Close successfully closes valid file descriptors without error
	var pipeFds [2]int
	if err := unix.Pipe(pipeFds[:]); err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: unix.Pipe failed: %v\n", err)
		os.Exit(1)
	}

	if err := unix.Close(pipeFds[0]); err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: unix.Close on read fd %d failed: %v\n", pipeFds[0], err)
		os.Exit(1)
	}
	if err := unix.Close(pipeFds[1]); err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: unix.Close on write fd %d failed: %v\n", pipeFds[1], err)
		os.Exit(1)
	}

	// Assertion 2: unix.Close returns EBADF when closing an invalid file descriptor
	if err := unix.Close(-1); err == nil {
		fmt.Fprintf(os.Stderr, "FAIL: unix.Close(-1) expected error, got nil\n")
		os.Exit(1)
	} else if !errors.Is(err, unix.EBADF) {
		fmt.Fprintf(os.Stderr, "FAIL: unix.Close(-1) expected EBADF, got %v\n", err)
		os.Exit(1)
	}

	// Assertion 3: unix.Close returns EBADF when attempting to close an already-closed file descriptor
	if err := unix.Close(pipeFds[0]); err == nil {
		fmt.Fprintf(os.Stderr, "FAIL: unix.Close on already closed fd %d expected error, got nil\n", pipeFds[0])
		os.Exit(1)
	} else if !errors.Is(err, unix.EBADF) {
		fmt.Fprintf(os.Stderr, "FAIL: unix.Close on already closed fd expected EBADF, got %v\n", err)
		os.Exit(1)
	}

	// Assertion 4: unix.Close on the write end of a pipe causes read on the read end to receive EOF
	var streamFds [2]int
	if err := unix.Pipe(streamFds[:]); err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: unix.Pipe for EOF test failed: %v\n", err)
		os.Exit(1)
	}
	defer unix.Close(streamFds[0])

	msg := []byte("data-before-close")
	if _, err := unix.Write(streamFds[1], msg); err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: unix.Write failed: %v\n", err)
		unix.Close(streamFds[1])
		os.Exit(1)
	}

	if err := unix.Close(streamFds[1]); err != nil {
		fmt.Fprintf(os.Stderr, "FAIL: unix.Close on stream write end failed: %v\n", err)
		os.Exit(1)
	}

	buf := make([]byte, 64)
	n, err := unix.Read(streamFds[0], buf)
	if err != nil || n != len(msg) {
		fmt.Fprintf(os.Stderr, "FAIL: unix.Read before EOF failed: n=%d, err=%v\n", n, err)
		os.Exit(1)
	}

	// Next read should return n=0, nil (EOF in Unix read syscall)
	n, err = unix.Read(streamFds[0], buf)
	if err != nil || n != 0 {
		fmt.Fprintf(os.Stderr, "FAIL: expected EOF (n=0, err=nil) after closing write end, got n=%d, err=%v\n", n, err)
		os.Exit(1)
	}

	fmt.Println("PASS: golang.org/x/sys/unix.Close contract passed")
}