whatcanGOwrong

go/pkg/mod/go.starlark.net@v0.0.0-20231101134539-556fd59b42f6/starlark/int_test.go

@@ -0,0 +1,157 @@
+// Copyright 2017 The Bazel Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package starlark
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"math"
+	"math/big"
+	"os"
+	"os/exec"
+	"runtime"
+	"strings"
+	"testing"
+)
+
+// TestIntOpts exercises integer arithmetic, especially at the boundaries.
+func TestIntOpts(t *testing.T) {
+	f := MakeInt64
+	left, right := big.NewInt(math.MinInt32), big.NewInt(math.MaxInt32)
+
+	for i, test := range []struct {
+		val  Int
+		want string
+	}{
+		// Add
+		{f(math.MaxInt32).Add(f(1)), "80000000"},
+		{f(math.MinInt32).Add(f(-1)), "-80000001"},
+		// Mul
+		{f(math.MaxInt32).Mul(f(math.MaxInt32)), "3fffffff00000001"},
+		{f(math.MinInt32).Mul(f(math.MinInt32)), "4000000000000000"},
+		{f(math.MaxUint32).Mul(f(math.MaxUint32)), "fffffffe00000001"},
+		{f(math.MinInt32).Mul(f(-1)), "80000000"},
+		// Div
+		{f(math.MinInt32).Div(f(-1)), "80000000"},
+		{f(1 << 31).Div(f(2)), "40000000"},
+		// And
+		{f(math.MaxInt32).And(f(math.MaxInt32)), "7fffffff"},
+		{f(math.MinInt32).And(f(math.MinInt32)), "-80000000"},
+		{f(1 << 33).And(f(1 << 32)), "0"},
+		// Mod
+		{f(1 << 32).Mod(f(2)), "0"},
+		// Or
+		{f(1 << 32).Or(f(0)), "100000000"},
+		{f(math.MaxInt32).Or(f(0)), "7fffffff"},
+		{f(math.MaxUint32).Or(f(0)), "ffffffff"},
+		{f(math.MinInt32).Or(f(math.MinInt32)), "-80000000"},
+		// Xor
+		{f(math.MinInt32).Xor(f(-1)), "7fffffff"},
+		// Not
+		{f(math.MinInt32).Not(), "7fffffff"},
+		{f(math.MaxInt32).Not(), "-80000000"},
+		// Shift
+		{f(1).Lsh(31), "80000000"},
+		{f(1).Lsh(32), "100000000"},
+		{f(math.MaxInt32 + 1).Rsh(1), "40000000"},
+		{f(math.MinInt32 * 2).Rsh(1), "-80000000"},
+	} {
+		if got := fmt.Sprintf("%x", test.val); got != test.want {
+			t.Errorf("%d equals %s, want %s", i, got, test.want)
+		}
+		small, big := test.val.get()
+		if small < math.MinInt32 || math.MaxInt32 < small {
+			t.Errorf("expected big, %d %s", i, test.val)
+		}
+		if big == nil {
+			continue
+		}
+		if small != 0 {
+			t.Errorf("expected 0 small, %d %s with %d", i, test.val, small)
+		}
+		if big.Cmp(left) >= 0 && big.Cmp(right) <= 0 {
+			t.Errorf("expected small, %d %s", i, test.val)
+		}
+	}
+}
+
+func TestImmutabilityMakeBigInt(t *testing.T) {
+	// use max int64 for the test
+	expect := int64(^uint64(0) >> 1)
+
+	mutint := big.NewInt(expect)
+	value := MakeBigInt(mutint)
+	mutint.Set(big.NewInt(1))
+
+	got, _ := value.Int64()
+	if got != expect {
+		t.Errorf("expected %d, got %d", expect, got)
+	}
+}
+
+func TestImmutabilityBigInt(t *testing.T) {
+	// use 1 and max int64 for the test
+	for _, expect := range []int64{1, int64(^uint64(0) >> 1)} {
+		value := MakeBigInt(big.NewInt(expect))
+
+		bigint := value.BigInt()
+		bigint.Set(big.NewInt(2))
+
+		got, _ := value.Int64()
+		if got != expect {
+			t.Errorf("expected %d, got %d", expect, got)
+		}
+	}
+}
+
+// TestIntFallback creates a small Int value in a child process with
+// limited address space to ensure that it still works, but prints a warning.
+func TestIntFallback(t *testing.T) {
+	if runtime.GOOS != "linux" {
+		t.Skipf("test disabled on this platform (requires ulimit -v)")
+	}
+	exe, err := os.Executable()
+	if err != nil {
+		t.Fatalf("can't find file name of executable: %v", err)
+	}
+	// ulimit -v limits the address space in KB. Not portable.
+	// 4GB is enough for the Go runtime but not for the optimization.
+	cmd := exec.Command("/bin/sh", "-c", fmt.Sprintf("ulimit -v 4000000 && %q --entry=intfallback", exe))
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("intfallback subcommand failed: %v\n%s", err, out)
+	}
+
+	// Check the warning was printed.
+	if !strings.Contains(string(out), "Integer performance may suffer") {
+		t.Errorf("expected warning was not printed. Output=<<%s>>", out)
+	}
+}
+
+// intfallback is called in a child process with limited address space.
+func intfallback() {
+	const want = 123
+	if got, _ := MakeBigInt(big.NewInt(want)).Int64(); got != want {
+		log.Fatalf("intfallback: got %d, want %d", got, want)
+	}
+}
+
+// The --entry flag invokes an alternate entry point, for use in subprocess tests.
+var testEntry = flag.String("entry", "", "child process entry-point")
+
+func TestMain(m *testing.M) {
+	// In some build systems, notably Blaze, flag.Parse is called before TestMain,
+	// in violation of the TestMain contract, making this second call a no-op.
+	flag.Parse()
+	switch *testEntry {
+	case "":
+		os.Exit(m.Run()) // normal case
+	case "intfallback":
+		intfallback()
+	default:
+		log.Fatalf("unknown entry point: %s", *testEntry)
+	}
+}