1 files changed, 78 insertions, 0 deletions
diff --git a/test/const7.go b/test/const7.go
new file mode 100644
index 0000000..a229fcc
--- /dev/null
+++ b/test/const7.go
@@ -0,0 +1,78 @@
+// run
+
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Check that the compiler refuses excessively long constants.
+
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+)
+
+// testProg creates a package called name, with path dir/name.go,
+// which declares an untyped constant of the given length.
+// testProg compiles this package and checks for the absence or
+// presence of a constant literal error.
+func testProg(dir, name string, length int, msg string) {
+	var buf bytes.Buffer
+
+	fmt.Fprintf(&buf,
+		"package %s; const _ = 0b%s // %d bits",
+		name, strings.Repeat("1", length), length,
+	)
+
+	filename := filepath.Join(dir, fmt.Sprintf("%s.go", name))
+	if err := os.WriteFile(filename, buf.Bytes(), 0666); err != nil {
+		log.Fatal(err)
+	}
+
+	cmd := exec.Command("go", "tool", "compile", "-p=p", filename)
+	cmd.Dir = dir
+	output, err := cmd.CombinedOutput()
+
+	if msg == "" {
+		// no error expected
+		if err != nil {
+			log.Fatalf("%s: compile failed unexpectedly: %v", name, err)
+		}
+		return
+	}
+
+	// error expected
+	if err == nil {
+		log.Fatalf("%s: compile succeeded unexpectedly", name)
+	}
+	if !bytes.Contains(output, []byte(msg)) {
+		log.Fatalf("%s: wrong compiler error message:\n%s\n", name, output)
+	}
+}
+
+func main() {
+	if runtime.GOOS == "js" || runtime.GOOS == "wasip1" || runtime.Compiler != "gc" {
+		return
+	}
+
+	dir, err := ioutil.TempDir("", "const7_")
+	if err != nil {
+		log.Fatalf("creating temp dir: %v\n", err)
+	}
+	defer os.RemoveAll(dir)
+
+	const bitLimit = 512
+	const charLimit = 10000 // compiler-internal constant length limit
+	testProg(dir, "x1", bitLimit, "")
+	testProg(dir, "x2", bitLimit+1, "constant overflow")
+	testProg(dir, "x3", charLimit-2, "constant overflow") // -2 because literal contains 0b prefix
+	testProg(dir, "x4", charLimit-1, "excessively long constant")
+}