goV = req.Version
			}
			if req.Path == "toolchain" {
				toolchain = req.Version
			}
		}
		return
	}
	oldGo, oldToolchain := toolchainVersions(oldReqs)
	newGo, newToolchain := toolchainVersions(newReqs)
	if oldGo != newGo {
		changes["go"] = change{"go", oldGo, newGo}
	}
	if oldToolchain != newToolchain {
		changes["toolchain"] = change{"toolchain", oldToolchain, newToolchain}
	}

	// toolchain you can download and run. In that case fall back to at least
	// checking that the toolchain is new enough for the Go version.
	toolchain := "go" + old
	if wf.Toolchain != nil {
		toolchain = wf.Toolchain.Name
	}
	if gover.IsLang(gover.Local()) {
		toolchain = gover.ToolchainMax(toolchain, "go"+goVers)
	} else {
		toolchain = gover.ToolchainMax(toolchain, "go"+gover.Local())
	}

	}

	// To recap, so far we have built the new toolchain
	// (cmd/asm, cmd/cgo, cmd/compile, cmd/link)
	// using the Go bootstrap toolchain and go command.
	// Then we built the new go command (as go_bootstrap)
	// using the new toolchain and our own build logic (above).
	//
	//	toolchain1 = mk(new toolchain, go1.17 toolchain, go1.17 cmd/go)
	//	go_bootstrap = mk(new cmd/go, toolchain1, cmd/dist)
	//

#     release_cpu_linux:               Toolchain and CUDA options for Linux CPU builds.
#     release_gpu_linux:               Toolchain and CUDA options for Linux GPU builds.
#     release_cpu_macos:               Toolchain and CUDA options for MacOS CPU builds.
#     release_cpu_windows:             Toolchain and CUDA options for Windows CPU builds.

==== Using invalid Java toolchain specifications

Usage of invalid Java toolchain specifications is no longer supported.
Related build errors can be avoided by making sure that language version is set on all toolchain specifications.
See <<toolchains#sec:configuring_toolchain_specifications,user manual>> for more information.

==== Using automatic toolchain downloading without having a repository configured

[[sec:defining_tool_chains]]
=== Defining tool chains

The supported tool chain types are:

* link:{groovyDslPath}/org.gradle.nativeplatform.toolchain.Gcc.html[Gcc]
* link:{groovyDslPath}/org.gradle.nativeplatform.toolchain.Clang.html[Clang]
* link:{groovyDslPath}/org.gradle.nativeplatform.toolchain.VisualCpp.html[VisualCpp]

=== Example: Defining tool chains

[source.multi-language-sample,groovy]
.build.gradle
----

+
You can bypass the toolchain discovery by specifying the installation directory of the version of Visual Studio you want via link:{groovyDslPath}/org.gradle.nativeplatform.toolchain.VisualCpp.html#org.gradle.nativeplatform.toolchain.VisualCpp:installDir[VisualCpp.setInstallDir(Object)].

== Upgrading from 8.8 and earlier

=== Potential breaking changes

==== Change to toolchain provisioning

	if v, ok := old.rootSelected("go"); ok {
		roots = append(roots, module.Version{Path: "go", Version: v})
		pathIsRoot["go"] = true
	}
	if v, ok := old.rootSelected("toolchain"); ok {
		roots = append(roots, module.Version{Path: "toolchain", Version: v})
		pathIsRoot["toolchain"] = true
	}
	// We start by adding roots for every package in "all".
	//
	// Once that is done, we may still need to add more roots to cover upgraded or

			} else {
				fatalf("Failed to set GOTRACEBACK: %v", err)
			}
		}
	}

	if t.rebuild {
		t.out("Building packages and commands.")
		// Force rebuild the whole toolchain.
		goInstall(toolenv(), gorootBinGo, append([]string{"-a"}, toolchain...)...)
	}

	if !t.listMode {
		if builder := os.Getenv("GO_BUILDER_NAME"); builder == "" {
			// Ensure that installed commands are up to date, even with -no-rebuild,