cmd/dist: do not unset GOROOT_FINAL prior to running tests

Also do not unset it by default in the tests for cmd/go.

GOROOT_FINAL affects the GOROOT value embedded in binaries,
such as 'cmd/cgo'. If its value changes and a build command
is performed that depends on one of those binaries, the binary
would be spuriously rebuilt.

Instead, only unset it in the specific tests that make assumptions
about the GOROOT paths embedded in specific compiled binaries.
That may cause those tests to do a little extra rebuilding when
GOROOT_FINAL is set, but that little bit of extra rebuilding
seems preferable to spuriously-stale binaries.

Fixes #39385

Change-Id: I7c87b1519bb5bcff64babf1505fd1033ffa4f4fb
Reviewed-on: https://go-review.googlesource.com/c/go/+/236819
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

9 files changed, 40 insertions, 18 deletions

diff --git a/src/cmd/addr2line/addr2line_test.go b/src/cmd/addr2line/addr2line_test.go
index 22bf1379bb..e12f0ae814 100644
--- a/src/cmd/addr2line/addr2line_test.go
+++ b/src/cmd/addr2line/addr2line_test.go
@@ -74,18 +74,26 @@ func testAddr2Line(t *testing.T, exepath, addr string) {
 		t.Fatalf("Stat failed: %v", err)
 	}
 	fi2, err := os.Stat(srcPath)
+	if gorootFinal := os.Getenv("GOROOT_FINAL"); gorootFinal != "" && strings.HasPrefix(srcPath, gorootFinal) {
+		if os.IsNotExist(err) || (err == nil && !os.SameFile(fi1, fi2)) {
+			// srcPath has had GOROOT_FINAL substituted for GOROOT, and it doesn't
+			// match the actual file. GOROOT probably hasn't been moved to its final
+			// location yet, so try the original location instead.
+			fi2, err = os.Stat(runtime.GOROOT() + strings.TrimPrefix(srcPath, gorootFinal))
+		}
+	}
 	if err != nil {
 		t.Fatalf("Stat failed: %v", err)
 	}
 	if !os.SameFile(fi1, fi2) {
 		t.Fatalf("addr2line_test.go and %s are not same file", srcPath)
 	}
-	if srcLineNo != "89" {
-		t.Fatalf("line number = %v; want 89", srcLineNo)
+	if srcLineNo != "97" {
+		t.Fatalf("line number = %v; want 97", srcLineNo)
 	}
 }
 
-// This is line 88. The test depends on that.
+// This is line 96. The test depends on that.
 func TestAddr2Line(t *testing.T) {
 	testenv.MustHaveGoBuild(t)
 
diff --git a/src/cmd/dist/test.go b/src/cmd/dist/test.go
index 08ef056164..e1cd4965c3 100644
--- a/src/cmd/dist/test.go
+++ b/src/cmd/dist/test.go
@@ -178,15 +178,6 @@ func (t *tester) run() {
 		return
 	}
 
-	// We must unset GOROOT_FINAL before tests, because runtime/debug requires
-	// correct access to source code, so if we have GOROOT_FINAL in effect,
-	// at least runtime/debug test will fail.
-	// If GOROOT_FINAL was set before, then now all the commands will appear stale.
-	// Nothing we can do about that other than not checking them below.
-	// (We call checkNotStale but only with "std" not "cmd".)
-	os.Setenv("GOROOT_FINAL_OLD", os.Getenv("GOROOT_FINAL")) // for cmd/link test
-	os.Unsetenv("GOROOT_FINAL")
-
 	for _, name := range t.runNames {
 		if !t.isRegisteredTestName(name) {
 			fatalf("unknown test %q", name)
diff --git a/src/cmd/go/go_test.go b/src/cmd/go/go_test.go
index 4c30de4781..021930a8a8 100644
--- a/src/cmd/go/go_test.go
+++ b/src/cmd/go/go_test.go
@@ -124,7 +124,6 @@ func TestMain(m *testing.M) {
 		fmt.Printf("SKIP\n")
 		return
 	}
-	os.Unsetenv("GOROOT_FINAL")
 
 	flag.Parse()
 
@@ -180,6 +179,11 @@ func TestMain(m *testing.M) {
 		}
 		testGOROOT = goEnv("GOROOT")
 		os.Setenv("TESTGO_GOROOT", testGOROOT)
+		// Ensure that GOROOT is set explicitly.
+		// Otherwise, if the toolchain was built with GOROOT_FINAL set but has not
+		// yet been moved to its final location, programs that invoke runtime.GOROOT
+		// may accidentally use the wrong path.
+		os.Setenv("GOROOT", testGOROOT)
 
 		// The whole GOROOT/pkg tree was installed using the GOHOSTOS/GOHOSTARCH
 		// toolchain (installed in GOROOT/pkg/tool/GOHOSTOS_GOHOSTARCH).
@@ -216,8 +220,10 @@ func TestMain(m *testing.M) {
 		}
 		testCC = strings.TrimSpace(string(out))
 
-		if out, err := exec.Command(testGo, "env", "CGO_ENABLED").Output(); err != nil {
-			fmt.Fprintf(os.Stderr, "running testgo failed: %v\n", err)
+		cmd := exec.Command(testGo, "env", "CGO_ENABLED")
+		cmd.Stderr = new(strings.Builder)
+		if out, err := cmd.Output(); err != nil {
+			fmt.Fprintf(os.Stderr, "running testgo failed: %v\n%s", err, cmd.Stderr)
 			canRun = false
 		} else {
 			canCgo, err = strconv.ParseBool(strings.TrimSpace(string(out)))
diff --git a/src/cmd/go/script_test.go b/src/cmd/go/script_test.go
index a49a705fa6..2e8f18a897 100644
--- a/src/cmd/go/script_test.go
+++ b/src/cmd/go/script_test.go
@@ -130,6 +130,7 @@ func (ts *testScript) setup() {
 		"GOPROXY=" + proxyURL,
 		"GOPRIVATE=",
 		"GOROOT=" + testGOROOT,
+		"GOROOT_FINAL=" + os.Getenv("GOROOT_FINAL"), // causes spurious rebuilds and breaks the "stale" built-in if not propagated
 		"TESTGO_GOROOT=" + testGOROOT,
 		"GOSUMDB=" + testSumDBVerifierKey,
 		"GONOPROXY=",
diff --git a/src/cmd/go/testdata/script/README b/src/cmd/go/testdata/script/README
index c7fa7cfef5..76d6651718 100644
--- a/src/cmd/go/testdata/script/README
+++ b/src/cmd/go/testdata/script/README
@@ -34,6 +34,7 @@ Scripts also have access to these other environment variables:
 	GOPATH=$WORK/gopath
 	GOPROXY=<local module proxy serving from cmd/go/testdata/mod>
 	GOROOT=<actual GOROOT>
+	GOROOT_FINAL=<actual GOROOT_FINAL>
 	TESTGO_GOROOT=<GOROOT used to build cmd/go, for use in tests that may change GOROOT>
 	HOME=/no-home
 	PATH=<actual PATH>
diff --git a/src/cmd/go/testdata/script/build_trimpath.txt b/src/cmd/go/testdata/script/build_trimpath.txt
index cfab80743e..ad78bcf2b2 100644
--- a/src/cmd/go/testdata/script/build_trimpath.txt
+++ b/src/cmd/go/testdata/script/build_trimpath.txt
@@ -1,5 +1,9 @@
 [short] skip
 
+# If GOROOT_FINAL is set, 'go build -trimpath' bakes that into the resulting
+# binary instead of GOROOT. Explicitly unset it here.
+env GOROOT_FINAL=
+
 # Set up two identical directories that can be used as GOPATH.
 env GO111MODULE=on
 mkdir $WORK/a/src/paths $WORK/b/src/paths
diff --git a/src/cmd/go/testdata/script/goroot_executable.txt b/src/cmd/go/testdata/script/goroot_executable.txt
index 4e04bad69b..fdbcde06cb 100644
--- a/src/cmd/go/testdata/script/goroot_executable.txt
+++ b/src/cmd/go/testdata/script/goroot_executable.txt
@@ -2,6 +2,13 @@
 
 mkdir $WORK/new/bin
 
+# In this test, we are specifically checking the logic for deriving
+# the value of GOROOT from runtime.GOROOT.
+# GOROOT_FINAL changes the default behavior of runtime.GOROOT,
+# and will thus cause the test to fail if it is set when our
+# new cmd/go is built.
+env GOROOT_FINAL=
+
 go build -o $WORK/new/bin/go$GOEXE cmd/go &
 go build -o $WORK/bin/check$GOEXE check.go &
 wait
diff --git a/src/cmd/link/dwarf_test.go b/src/cmd/link/dwarf_test.go
index 5926f09e4a..a9f58db230 100644
--- a/src/cmd/link/dwarf_test.go
+++ b/src/cmd/link/dwarf_test.go
@@ -33,8 +33,8 @@ func testDWARF(t *testing.T, buildmode string, expectDWARF bool, env ...string)
 		t.Fatalf("go list: %v\n%s", err, out)
 	}
 	if string(out) != "false\n" {
-		if os.Getenv("GOROOT_FINAL_OLD") != "" {
-			t.Skip("cmd/link is stale, but $GOROOT_FINAL_OLD is set")
+		if strings.HasPrefix(testenv.Builder(), "darwin-") {
+			t.Skipf("cmd/link is spuriously stale on Darwin builders - see #33598")
 		}
 		t.Fatalf("cmd/link is stale - run go install cmd/link")
 	}
diff --git a/src/cmd/objdump/objdump_test.go b/src/cmd/objdump/objdump_test.go
index c974d6707b..a9dc7d1a5e 100644
--- a/src/cmd/objdump/objdump_test.go
+++ b/src/cmd/objdump/objdump_test.go
@@ -138,7 +138,11 @@ func testDisasm(t *testing.T, printCode bool, printGnuAsm bool, flags ...string)
 	args = append(args, flags...)
 	args = append(args, "fmthello.go")
 	cmd := exec.Command(testenv.GoToolPath(t), args...)
-	cmd.Dir = "testdata" // "Bad line" bug #36683 is sensitive to being run in the source directory
+	// "Bad line" bug #36683 is sensitive to being run in the source directory.
+	cmd.Dir = "testdata"
+	// Ensure that the source file location embedded in the binary matches our
+	// actual current GOROOT, instead of GOROOT_FINAL if set.
+	cmd.Env = append(os.Environ(), "GOROOT_FINAL=")
 	t.Logf("Running %v", cmd.Args)
 	out, err := cmd.CombinedOutput()
 	if err != nil {