1// run
2
3// Copyright 2021 The Go Authors. All rights reserved.
4// Use of this source code is governed by a BSD-style
5// license that can be found in the LICENSE file.
6
7// Check that the compiler refuses excessively long constants.
8
9package main
10
11import (
12	"bytes"
13	"fmt"
14	"io/ioutil"
15	"log"
16	"os"
17	"os/exec"
18	"path/filepath"
19	"runtime"
20	"strings"
21)
22
23// testProg creates a package called name, with path dir/name.go,
24// which declares an untyped constant of the given length.
25// testProg compiles this package and checks for the absence or
26// presence of a constant literal error.
27func testProg(dir, name string, length int, msg string) {
28	var buf bytes.Buffer
29
30	fmt.Fprintf(&buf,
31		"package %s; const _ = 0b%s // %d bits",
32		name, strings.Repeat("1", length), length,
33	)
34
35	filename := filepath.Join(dir, fmt.Sprintf("%s.go", name))
36	if err := os.WriteFile(filename, buf.Bytes(), 0666); err != nil {
37		log.Fatal(err)
38	}
39
40	cmd := exec.Command("go", "tool", "compile", "-p=p", filename)
41	cmd.Dir = dir
42	output, err := cmd.CombinedOutput()
43
44	if msg == "" {
45		// no error expected
46		if err != nil {
47			log.Fatalf("%s: compile failed unexpectedly: %v", name, err)
48		}
49		return
50	}
51
52	// error expected
53	if err == nil {
54		log.Fatalf("%s: compile succeeded unexpectedly", name)
55	}
56	if !bytes.Contains(output, []byte(msg)) {
57		log.Fatalf("%s: wrong compiler error message:\n%s\n", name, output)
58	}
59}
60
61func main() {
62	if runtime.GOOS == "js" || runtime.GOOS == "wasip1" || runtime.Compiler != "gc" {
63		return
64	}
65
66	dir, err := ioutil.TempDir("", "const7_")
67	if err != nil {
68		log.Fatalf("creating temp dir: %v\n", err)
69	}
70	defer os.RemoveAll(dir)
71
72	const bitLimit = 512
73	const charLimit = 10000 // compiler-internal constant length limit
74	testProg(dir, "x1", bitLimit, "")
75	testProg(dir, "x2", bitLimit+1, "constant overflow")
76	testProg(dir, "x3", charLimit-2, "constant overflow") // -2 because literal contains 0b prefix
77	testProg(dir, "x4", charLimit-1, "excessively long constant")
78}
79