The tool chain and runtime also have regular Go tests in their packages.
The main reasons to add a new test to this directory are:

* it is most naturally expressed using the test runner; or

// compile

// Copyright 2022 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Crashed gccgo.

package p

var F func() [0]struct{
	A int
}

var i int

// compile

// Copyright 2022 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Crashed gccgo.

package p

var F func([0]int) int
var G func() [0]int

}

// gccgoToSymbol converts a name to a mangled symbol for gccgo.
func gccgoToSymbol(ppath string) string {
	if gccgoMangler == nil {
		var err error
		cmd := os.Getenv("GCCGO")
		if cmd == "" {
			cmd, err = exec.LookPath("gccgo")
			if err != nil {
				fatalf("unable to locate gccgo: %v", err)
			}
		}
		gccgoMangler, err = pkgpath.ToSymbolFunc(cmd, *objDir)

// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

//go:build cgo

// Issue 8828: compiling a file with -compiler=gccgo fails if a .c file
// has the same name as compiled directory.

package cgotest

import "cmd/cgo/internal/test/issue8828"

func p() {
	issue8828.Bar()

// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

//go:build gccgo && linux && amd64

package unix

import "syscall"

//extern gettimeofday
func realGettimeofday(*Timeval, *byte) int32

func gettimeofday(tv *Timeval) (err syscall.Errno) {
	r := realGettimeofday(tv, nil)
	if r < 0 {
		return syscall.GetErrno()
	}

cd ../testinternal2
env GO111MODULE=off
! go build -v .
stderr 'p\.go:3:8: use of internal package .*internal/w not allowed'
env GO111MODULE=''

[compiler:gccgo] skip # gccgo does not have GOROOT
cd ../testinternal
! go build -v .
stderr 'p\.go:3:8: use of internal package net/http/internal not allowed'

-- testinternal/go.mod --
module testinternal

go 1.16
-- testinternal/p.go --

// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

//go:build (386 || amd64 || amd64p32) && gccgo

#include <cpuid.h>
#include <stdint.h>
#include <x86intrin.h>

// Need to wrap __get_cpuid_count because it's declared as static.
int
gccgoGetCpuidCount(uint32_t leaf, uint32_t subleaf,
                   uint32_t *eax, uint32_t *ebx,

env GO111MODULE=off

# gccgo does not have standard packages.
[compiler:gccgo] skip

# fmt should have no rewritten imports.
# The import from a/b should map c/d to a's vendor directory.
go list -f '{{.ImportPath}}: {{.ImportMap}}' fmt a/b
stdout 'fmt: map\[\]'
stdout 'a/b: map\[c/d:a/vendor/c/d\]'

# flag [fmt.test] should import fmt [fmt.test] as fmt
# fmt.test should import testing [fmt.test] as testing
# fmt.test should not import a modified os

				// Fake packages - nothing to build.
				a.Mode = "built-in package"
				a.Actor = nil
				return a
			}

			// gccgo standard library is "fake" too.
			if cfg.BuildToolchainName == "gccgo" {
				// the target name is needed for cgo.
				a.Mode = "gccgo stdlib"
				a.Target = p.Target
				a.Actor = nil
				return a
			}
		}

		return a
	})