go/ssa/interp: avoid hard-coding GOOS and GOARCH

GOOS and GOARCH are not necessarily present in the environment at all,
so overriding them in interp doesn't have a clear purpose, especially
given that CL 495255 no longer overrides them in the build context.

Unfortunately, the fake (reduced) GOROOT/src used for the test also
hard-coded the runtime constants for GOOS and GOARCH. Since in general
the testdata directory is not writable (it may be in the module
cache), we need to copy the fake GOROOT into a testdata directory in
order to modify it.

This change also deletes an unused function that I noticed while
investigating.

Fixes golang/go#60226 (maybe).

Change-Id: I409292af76d411efb8a3b4ca6d8d929b53325610
Reviewed-on: https://go-review.googlesource.com/c/tools/+/495258
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Robert Findley <[email protected]>
Auto-Submit: Bryan Mills <[email protected]>
gopls-CI: kokoro <[email protected]>
Run-TryBot: Bryan Mills <[email protected]>

Author: Bryan C. Mills

go/ssa/interp/external.go

@@ -312,10 +312,6 @@ func ext۰os۰Getenv(fr *frame, args []value) value {
 	switch name {
 	case "GOSSAINTERP":
 		return "1"
-	case "GOARCH":
-		return "amd64"
-	case "GOOS":
-		return "linux"
 	}
 	return os.Getenv(name)
 }

go/ssa/interp/interp.go

@@ -635,15 +635,6 @@ func doRecover(caller *frame) value {
 	return iface{}
 }
 
-// setGlobal sets the value of a system-initialized global variable.
-func setGlobal(i *interpreter, pkg *ssa.Package, name string, v value) {
-	if g, ok := i.globals[pkg.Var(name)]; ok {
-		*g = v
-		return
-	}
-	panic("no global variable: " + pkg.Pkg.Path() + "." + name)
-}
-
 // Interpret interprets the Go program whose main package is mainpkg.
 // mode specifies various interpreter options.  filename and args are
 // the initial values of os.Args for the target program.  sizes is the

go/ssa/interp/interp_test.go

@@ -138,9 +138,14 @@ func init() {
 		testdataTests = append(testdataTests, "typeassert.go")
 		testdataTests = append(testdataTests, "zeros.go")
 	}
+
+	// GOROOT/test used to assume that GOOS and GOARCH were explicitly set in the
+	// environment, so do that here for TestGorootTest.
+	os.Setenv("GOOS", runtime.GOOS)
+	os.Setenv("GOARCH", runtime.GOARCH)
 }
 
-func run(t *testing.T, input string) {
+func run(t *testing.T, input string, goroot string) {
 	// The recover2 test case is broken on Go 1.14+. See golang/go#34089.
 	// TODO(matloob): Fix this.
 	if filepath.Base(input) == "recover2.go" {
@@ -151,8 +156,8 @@ func run(t *testing.T, input string) {
 
 	start := time.Now()
 
-	ctx := build.Default    // copy
-	ctx.GOROOT = "testdata" // fake goroot
+	ctx := build.Default // copy
+	ctx.GOROOT = goroot
 	ctx.GOOS = runtime.GOOS
 	ctx.GOARCH = runtime.GOARCH
 	if filepath.Base(input) == "width32.go" && unsafe.Sizeof(int(0)) > 4 {
@@ -222,24 +227,72 @@ func run(t *testing.T, input string) {
 	}
 }
 
+// makeGoroot copies testdata/src into the "src" directory of a temporary
+// location to mimic GOROOT/src, and adds a file "runtime/consts.go" containing
+// declarations for GOOS and GOARCH that match the GOOS and GOARCH of this test.
+//
+// It returns the directory that should be used for GOROOT.
+func makeGoroot(t *testing.T) string {
+	goroot := t.TempDir()
+	src := filepath.Join(goroot, "src")
+
+	err := filepath.Walk("testdata/src", func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+
+		rel, err := filepath.Rel("testdata/src", path)
+		if err != nil {
+			return err
+		}
+		targ := filepath.Join(src, rel)
+
+		if info.IsDir() {
+			return os.Mkdir(targ, info.Mode().Perm()|0700)
+		}
+
+		b, err := os.ReadFile(path)
+		if err != nil {
+			return err
+		}
+		return os.WriteFile(targ, b, info.Mode().Perm())
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	constsGo := fmt.Sprintf(`package runtime
+const GOOS = %q
+const GOARCH = %q
+`, runtime.GOOS, runtime.GOARCH)
+	err = os.WriteFile(filepath.Join(src, "runtime/consts.go"), []byte(constsGo), 0644)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	return goroot
+}
+
 // TestTestdataFiles runs the interpreter on testdata/*.go.
 func TestTestdataFiles(t *testing.T) {
+	goroot := makeGoroot(t)
 	cwd, err := os.Getwd()
 	if err != nil {
 		log.Fatal(err)
 	}
 	for _, input := range testdataTests {
 		t.Run(input, func(t *testing.T) {
-			run(t, filepath.Join(cwd, "testdata", input))
+			run(t, filepath.Join(cwd, "testdata", input), goroot)
 		})
 	}
 }
 
 // TestGorootTest runs the interpreter on $GOROOT/test/*.go.
 func TestGorootTest(t *testing.T) {
+	goroot := makeGoroot(t)
 	for _, input := range gorootTestTests {
 		t.Run(input, func(t *testing.T) {
-			run(t, filepath.Join(build.Default.GOROOT, "test", input))
+			run(t, filepath.Join(build.Default.GOROOT, "test", input), goroot)
 		})
 	}
 }
@@ -251,6 +304,7 @@ func TestTypeparamTest(t *testing.T) {
 	if !typeparams.Enabled {
 		return
 	}
+	goroot := makeGoroot(t)
 
 	// Skip known failures for the given reason.
 	// TODO(taking): Address these.
@@ -295,7 +349,7 @@ func TestTypeparamTest(t *testing.T) {
 				t.Skipf("skipping: %s", reason)
 			}
 
-			run(t, input)
+			run(t, input, goroot)
 		})
 	}
 }

go/ssa/interp/testdata/src/runtime/runtime.go

@@ -16,7 +16,4 @@ type Error interface {
 	RuntimeError()
 }
 
-const GOOS = "linux"
-const GOARCH = "amd64"
-
 func GC()