if !ok {
				t.Errorf("package %s: missing feature %q", fi.Name(), feature)
			}
			delete(w.features, feature)
		}

		for _, feature := range w.Features() {
			t.Errorf("package %s: extra feature not in golden file: %q", fi.Name(), feature)
		}
	}
}

func TestCompareAPI(t *testing.T) {
	tests := []struct {
		name                          string
		features, required, exception []string

name: Pkg.go.dev bugs or feature requests
description: Issues or feature requests for the documentation site
title: "x/pkgsite: issue title"
labels: ["pkgsite"]
body:
  - type: markdown
    attributes:
      value: "Please answer these questions before submitting your issue. Thanks!"
  - type: input
    id: url
    attributes:
      label: "What is the URL of the page with the issue?"
    validations:
      required: true
  - type: input

needing to process arbitrary .o files. It only needs to process the .o
files generated from C files that cgo writes, and those are much more
limited in the ELF or other features that they use.

In essence, the _cgo_import.o file includes the extra linking
directives that cmd/link is not sophisticated enough to derive from _all.o
on its own. Similarly, the _all.o uses dynamic references to real

    validations:
      required: true

  - type: textarea
    id: orthogonality
    attributes:
      label: "Orthogonality: How does this change interact or overlap with existing features?"
      description: "Is the goal of this change a performance improvement? If so, what quantifiable improvement should we expect? How would we measure it?"
    validations:
      required: false

  - type: textarea

/* An example of writing a C++ virtual function in Go.  */

%module(directors="1") callback

%{
#include <string>
#include "main.h"
%}

%include "std_string.i"

%feature("director");

)

// basicKeys is a set of the PAX keys for which we have built-in support.
// This does not contain "charset" or "comment", which are both PAX-specific,
// so adding them as first-class features of Header is unlikely.
// Users can use the PAXRecords field to set it themselves.
var basicKeys = map[string]bool{
	paxPath: true, paxLinkpath: true, paxSize: true, paxUid: true, paxGid: true,

// the integer type used to store each numeric field
// (where timestamps are stored as the number of seconds since the Unix epoch).
//
// The table's lower portion shows specialized features of each format,
// such as supported string encodings, support for sub-second timestamps,
// or support for sparse files.
//
// The Writer currently provides no support for sparse files.
type Format int

Each file is a list of API features, one per line.

go1.txt (and similarly named files) are frozen once a version has been
shipped. Each file adds new lines but does not remove any.

except.txt lists features that may disappear without breaking true
compatibility.

Starting with go1.19.txt, each API feature line must end in "#nnnnn"

pkg syscall (linux-386), const RTAX_CWND ideal-int
pkg syscall (linux-386), const RTAX_FEATURES ideal-int
pkg syscall (linux-386), const RTAX_FEATURE_ALLFRAG ideal-int
pkg syscall (linux-386), const RTAX_FEATURE_ECN ideal-int
pkg syscall (linux-386), const RTAX_FEATURE_SACK ideal-int
pkg syscall (linux-386), const RTAX_FEATURE_TIMESTAMP ideal-int
pkg syscall (linux-386), const RTAX_HOPLIMIT ideal-int

There are, however, times when we cannot maintain complete compatibility.
If code depends on buggy (including insecure) behavior,
then fixing the bug will break that code.
New features can also have similar impacts:
enabling the HTTP/2 use by the HTTP client broke programs
connecting to servers with buggy HTTP/2 implementations.
These kinds of changes are unavoidable and