codekingpro/portable-devtools

1// Copyright 2023 The Go Authors. All rights reserved.2// Use of this source code is governed by a BSD-style3// license that can be found in the LICENSE file.4 5package rand_test6 7import (8	"fmt"9	"internal/race"10	"internal/testenv"11	. "math/rand"12	"os"13	"runtime"14	"strconv"15	"sync"16	"testing"17)18 19// Test that racy access to the default functions behaves reasonably.20func TestDefaultRace(t *testing.T) {21	// Skip the test in short mode, but even in short mode run22	// the test if we are using the race detector, because part23	// of this is to see whether the race detector reports any problems.24	if testing.Short() && !race.Enabled {25		t.Skip("skipping starting another executable in short mode")26	}27 28	const env = "GO_RAND_TEST_HELPER_CODE"29	if v := os.Getenv(env); v != "" {30		doDefaultTest(t, v)31		return32	}33 34	t.Parallel()35 36	for i := 0; i < 6; i++ {37		t.Run(strconv.Itoa(i), func(t *testing.T) {38			t.Parallel()39			cmd := testenv.Command(t, testenv.Executable(t), "-test.run=^TestDefaultRace$")40			cmd = testenv.CleanCmdEnv(cmd)41			cmd.Env = append(cmd.Env, fmt.Sprintf("GO_RAND_TEST_HELPER_CODE=%d", i/2))42			if i%2 != 0 {43				cmd.Env = append(cmd.Env, "GODEBUG=randautoseed=0")44			}45			out, err := cmd.CombinedOutput()46			if len(out) > 0 {47				t.Logf("%s", out)48			}49			if err != nil {50				t.Error(err)51			}52		})53	}54}55 56// doDefaultTest should be run before there have been any calls to the57// top-level math/rand functions. Make sure that we can make concurrent58// calls to top-level functions and to Seed without any duplicate values.59// This will also give the race detector a change to report any problems.60func doDefaultTest(t *testing.T, v string) {61	code, err := strconv.Atoi(v)62	if err != nil {63		t.Fatalf("internal error: unrecognized code %q", v)64	}65 66	goroutines := runtime.GOMAXPROCS(0)67	if goroutines < 4 {68		goroutines = 469	}70 71	ch := make(chan uint64, goroutines*3)72	var wg sync.WaitGroup73 74	// The various tests below should not cause race detector reports75	// and should not produce duplicate results.76	//77	// Note: these tests can theoretically fail when using fastrand6478	// in that it is possible to coincidentally get the same random79	// number twice. That could happen something like 1 / 2**64 times,80	// which is rare enough that it may never happen. We don't worry81	// about that case.82 83	switch code {84	case 0:85		// Call Seed and Uint64 concurrently.86		wg.Add(goroutines)87		for i := 0; i < goroutines; i++ {88			go func(s int64) {89				defer wg.Done()90				Seed(s)91			}(int64(i) + 100)92		}93		wg.Add(goroutines)94		for i := 0; i < goroutines; i++ {95			go func() {96				defer wg.Done()97				ch <- Uint64()98			}()99		}100	case 1:101		// Call Uint64 concurrently with no Seed.102		wg.Add(goroutines)103		for i := 0; i < goroutines; i++ {104			go func() {105				defer wg.Done()106				ch <- Uint64()107			}()108		}109	case 2:110		// Start with Uint64 to pick the fast source, then call111		// Seed and Uint64 concurrently.112		ch <- Uint64()113		wg.Add(goroutines)114		for i := 0; i < goroutines; i++ {115			go func(s int64) {116				defer wg.Done()117				Seed(s)118			}(int64(i) + 100)119		}120		wg.Add(goroutines)121		for i := 0; i < goroutines; i++ {122			go func() {123				defer wg.Done()124				ch <- Uint64()125			}()126		}127	default:128		t.Fatalf("internal error: unrecognized code %d", code)129	}130 131	go func() {132		wg.Wait()133		close(ch)134	}()135 136	m := make(map[uint64]bool)137	for i := range ch {138		if m[i] {139			t.Errorf("saw %d twice", i)140		}141		m[i] = true142	}143}144