must be placed in preambles in other files, or in C source files.

# Passing pointers

Go is a garbage collected language, and the garbage collector needs to
know the location of every pointer to Go memory. Because of this,
there are restrictions on passing pointers between Go and C.

In this section the term Go pointer means a pointer to memory
allocated by Go (such as by using the & operator or calling the

</p>

<p>
Implementation restriction: Although numeric constants have arbitrary
precision in the language, a compiler may implement them using an
internal representation with limited precision.  That said, every
implementation must:
</p>

<ul>
	<li>Represent integer constants with at least 256 bits.</li>

	<li>Represent floating-point constants, including the parts of

	// uncompressed expected content.
	// If content is very large, an alternative to setting Content or File
	// is to set Size, which will then be checked against the header-reported size
	// but will bypass the decompressing of the actual data.
	// This last option is used for testing very large (multi-GB) compressed files.
	ContentErr error
	Content    []byte
	File       string

  - type: textarea
    id: cost-description
    attributes:
      label: "Cost Description"
      description: "What is the cost of this proposal? (Every language change has a cost)"

  - type: input
    id: go-toolchain
    attributes:
      label: Changes to Go ToolChain

//
//go:build linux

package bytes_test

import (
	. "bytes"
	"syscall"
	"testing"
)

// This file tests the situation where byte operations are checking
// data very near to a page boundary. We want to make sure those
// operations do not read across the boundary and cause a page
// fault where they shouldn't.

// These tests run only on linux. The code being tested is

	// the BSD tar utility.
	if size < 0 {
		return false
	}
	var pre sparseEntry
	for _, cur := range sp {
		switch {
		case cur.Offset < 0 || cur.Length < 0:
			return false // Negative values are never okay
		case cur.Offset > math.MaxInt64-cur.Length:
			return false // Integer overflow with large length
		case cur.endOffset() > size:
			return false // Region extends beyond the actual size

				Name:   "foo",
				Method: Deflate,
			})
			w.Write(bigBuf)
		}
		zw.Close()
	}

	b.ReportAllocs()
	// Run once and then reset the timer.
	// This effectively discards the very large initial flate setup cost,
	// as well as the initialization of bigBuf.
	runOnce(&bytes.Buffer{})
	b.ResetTimer()

	b.RunParallel(func(pb *testing.PB) {
		var buf bytes.Buffer
		for pb.Next() {

	// Minimum alignment for a struct is 1 byte.
	align = 1

	var buf strings.Builder
	buf.WriteString("struct {")
	fld := make([]*ast.Field, 0, 2*len(dt.Field)+1) // enough for padding around every field
	sizes := make([]int64, 0, 2*len(dt.Field)+1)
	off := int64(0)

	// Rename struct fields that happen to be named Go keywords into
	// _{keyword}.  Create a map from C ident -> Go ident. The Go ident will

	FMOVS	0x1002ffc(R1), F2	// FMOVS	16789500(R1), F2	// 3bfc7f9162ff7fbd
	FMOVD	0x8008(R1), F2		// FMOVD	32776(R1), F2		// 3b204091620740fd
	FMOVD	0x1006ff8(R1), F2	// FMOVD	16805880(R1), F2	// 3bfc7f9162ff7ffd

// very large or unaligned offset uses constant pool.
// the encoding cannot be checked as the address of the constant pool is unknown.
// here we only test that they can be assembled.
	MOVB	R1, 0x1000000(R2)	// MOVB		R1, 16777216(R2)

is in a module with a `go.mod` `go` line using Go 1.23.0 or later.
When Go 1.23 builds older programs, the old behaviors remain in effect.
The new [GODEBUG setting](/doc/godebug) [`asynctimerchan=1`](/pkg/time/#NewTimer)
can be used to revert back to asynchronous channel behaviors