[dev.fuzz] internal/fuzz: write a newline to the end of a corpus file

If someone manually adds/alters a corpus file to add
extra spacing or remove the final newline, the file
can still be decoded. However, this change ensures that
the fuzzing engine correctly writes the final newline.

Fixes golang/go#48130

Change-Id: Ib5556d4a6e4e0bfd9bc2edab357b7c25bedfd176
Reviewed-on: https://go-review.googlesource.com/c/go/+/349055
Trust: Katie Hockman <katie@golang.org>
Run-TryBot: Katie Hockman <katie@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>

diff --git a/src/cmd/go/testdata/script/test_fuzz_minimize.txt b/src/cmd/go/testdata/script/test_fuzz_minimize.txt
index ea1ee764741154aaaf1d64c2d5b7fd8e42fb4a4d..dac11231ef93c81c5371b42a5942648b5c5f6dda 100644 (file)
--- a/src/cmd/go/testdata/script/test_fuzz_minimize.txt
+++ b/src/cmd/go/testdata/script/test_fuzz_minimize.txt
@@ -163,6 +163,9 @@ func main() {
                os.Exit(1)
        }
 
+       // Trim the newline at the end of the file
+       got = bytes.TrimSpace(got)
+
        // Make sure that there were exactly 100 bytes written to the corpus entry
        prefix := []byte("[]byte(")
        i := bytes.Index(got, prefix)

diff --git a/src/internal/fuzz/encoding.go b/src/internal/fuzz/encoding.go
index c2f7d22b752c3622d12fe4505cf9a63e87b855f5..d3f24c3e6c8dbdcf3858bbd3fdd196a184732fc8 100644 (file)
--- a/src/internal/fuzz/encoding.go
+++ b/src/internal/fuzz/encoding.go
@@ -22,21 +22,21 @@ func marshalCorpusFile(vals ...interface{}) []byte {
        if len(vals) == 0 {
                panic("must have at least one value to marshal")
        }
-       b := bytes.NewBuffer([]byte(encVersion1))
+       b := bytes.NewBuffer([]byte(encVersion1 + "\n"))
        // TODO(katiehockman): keep uint8 and int32 encoding where applicable,
        // instead of changing to byte and rune respectively.
        for _, val := range vals {
                switch t := val.(type) {
                case int, int8, int16, int64, uint, uint16, uint32, uint64, float32, float64, bool:
-                       fmt.Fprintf(b, "\n%T(%v)", t, t)
+                       fmt.Fprintf(b, "%T(%v)\n", t, t)
                case string:
-                       fmt.Fprintf(b, "\nstring(%q)", t)
+                       fmt.Fprintf(b, "string(%q)\n", t)
                case rune: // int32
-                       fmt.Fprintf(b, "\nrune(%q)", t)
+                       fmt.Fprintf(b, "rune(%q)\n", t)
                case byte: // uint8
-                       fmt.Fprintf(b, "\nbyte(%q)", t)
+                       fmt.Fprintf(b, "byte(%q)\n", t)
                case []byte: // []uint8
-                       fmt.Fprintf(b, "\n[]byte(%q)", t)
+                       fmt.Fprintf(b, "[]byte(%q)\n", t)
                default:
                        panic(fmt.Sprintf("unsupported type: %T", t))
                }

diff --git a/src/internal/fuzz/encoding_test.go b/src/internal/fuzz/encoding_test.go
index 314f82a9956ef350bcd75a86fa1289994c01da26..b429d429c673723203ca324a870369dfa5f9d82f 100644 (file)
--- a/src/internal/fuzz/encoding_test.go
+++ b/src/internal/fuzz/encoding_test.go
@@ -66,16 +66,21 @@ byte('☃')`,
                },
                {
                        in: `go test fuzz v1
+string("has final newline")
+`,
+                       ok: true, // has final newline
+               },
+               {
+                       in: `go test fuzz v1
 string("extra")
 []byte("spacing")  
     `,
-                       ok: true,
+                       ok: true, // extra spaces in the final newline
                },
                {
                        in: `go test fuzz v1
 float64(0)
-float32(0)
-`,
+float32(0)`,
                        ok: true, // will be an integer literal since there is no decimal
                },
                {
@@ -114,9 +119,12 @@ float32(2.5)`,
                        if err != nil {
                                t.Fatalf("marshal unexpected error: %v", err)
                        }
-                       want := strings.TrimSpace(test.in)
-                       if want != string(newB) {
-                               t.Errorf("values changed after unmarshal then marshal\nbefore: %q\nafter:  %q", want, newB)
+                       if newB[len(newB)-1] != '\n' {
+                               t.Error("didn't write final newline to corpus file")
+                       }
+                       before, after := strings.TrimSpace(test.in), strings.TrimSpace(string(newB))
+                       if before != after {
+                               t.Errorf("values changed after unmarshal then marshal\nbefore: %q\nafter:  %q", before, after)
                        }
                })
        }