---
title: "Go, Backwards Compatibility, and GODEBUG"
layout: article
---

<!--
This document is kept in the Go repo, not x/website,
because it documents the full list of known GODEBUG settings,
which are tied to a specific release.
-->

## Introduction {#intro}

Go's emphasis on backwards compatibility is one of its key strengths.
There are, however, times when we cannot maintain complete compatibility.

   * Whenever an implementation uses `instanceof` on a parameter instance, the test has to know that
   * (so much for "black box") and try instances that both do and don't pass the check. The "don't"
   * half of that is more awkward to arrange...
   */
  private static <T> Iterable<T> iterable(Collection<T> collection) {
    // return collection::iterator;
    return new Iterable<T>() {
      @Override
      public Iterator<T> iterator() {

                .build());
        options.addOption(Option.builder(Character.toString(BATCH_MODE))
                .longOpt("batch-mode")
                .desc("Run in non-interactive mode. Alias for --non-interactive (kept for backwards compatability)")
                .build());
        options.addOption(Option.builder()
                .longOpt(NON_INTERACTIVE)
                .desc("Run in non-interactive mode. Alias for --batch-mode")

              <include>org.apache.maven.toolchain</include>
              <include>org.apache.maven.usability</include>
            </includes>
            <!-- allowed non-binary backwards compatible changes -->
            <excludes>
              <!-- START default constructor on Plexus/JSR 330 components -->

 *   <li>Improved memory compactness and locality.
 *   <li>Can be queried without allocating garbage.
 *   <li>Access to {@code LongStream} features (like {@link LongStream#sum}) using {@code stream()}
 *       instead of the awkward {@code stream().mapToLong(v -> v)}.
 * </ul>
 *
 * <p>Disadvantages compared to {@code ImmutableList<Long>}:
 *
 * <ul>
 *   <li>Can't be passed directly to methods that expect {@code Iterable}, {@code Collection}, or

   * Whenever an implementation uses `instanceof` on a parameter instance, the test has to know that
   * (so much for "black box") and try instances that both do and don't pass the check. The "don't"
   * half of that is more awkward to arrange...
   */
  private static <T> Iterable<T> iterable(Collection<T> collection) {
    // return collection::iterator;
    return new Iterable<T>() {
      @Override
      public Iterator<T> iterator() {

      errorCode != null -> throw errorException ?: StreamResetException(errorCode!!)
    }
  }

  /**
   * Like [Object.wait], but throws an [InterruptedIOException] when interrupted instead of the more
   * awkward [InterruptedException].
   */
  @Throws(InterruptedIOException::class)
  internal fun waitForIo() {
    try {
      wait()
    } catch (_: InterruptedException) {

        // First byte should be length of "test" (4) after processing
        assertEquals(4, dst[0]);

        // After processing, dots should be replaced with length markers
        // The scope processing happens backwards
        assertEquals(name.scope.length() + 2, length);
    }

    @Test
    void readScopeWireFormat_withMultipleLabels_shouldParseCorrectly() {
        byte[] src = new byte[100];

   * Whenever an implementation uses `instanceof` on a parameter instance, the test has to know that
   * (so much for "black box") and try instances that both do and don't pass the check. The "don't"
   * half of that is more awkward to arrange...
   */
  private static <T> Iterable<T> iterable(Collection<T> collection) {
    // return collection::iterator;
    return new Iterable<T>() {
      @Override
      public Iterator<T> iterator() {

   * Whenever an implementation uses `instanceof` on a parameter instance, the test has to know that
   * (so much for "black box") and try instances that both do and don't pass the check. The "don't"
   * half of that is more awkward to arrange...
   */
  private static <T> Iterable<T> iterable(Collection<T> collection) {
    // return collection::iterator;
    return new Iterable<T>() {
      @Override
      public Iterator<T> iterator() {