encoding/gob: update decgen to generate current dec_helpers

I edited dec_helpers.go without realizing that it is a generated file.
Fix the generator to generate the current version (which generates
a small comment change).

Change-Id: I70e3bc78eb0728d23c08972611218f288dc1d29c
Reviewed-on: https://go-review.googlesource.com/c/go/+/479117
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Andrew Ekstedt <andrew.ekstedt@gmail.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Auto-Submit: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>

diff --git a/src/encoding/gob/dec_helpers.go b/src/encoding/gob/dec_helpers.go
index 098ba7254a21ed0f77743c792c4faa210b13c51c..44a74e24427987ae504bf77531659ae757c906df 100644 (file)
--- a/src/encoding/gob/dec_helpers.go
+++ b/src/encoding/gob/dec_helpers.go
@@ -359,6 +359,7 @@ func decStringSlice(state *decoderState, v reflect.Value, length int, ovfl error
                        errorf("decoding string array or slice: length exceeds input size (%d elements)", length)
                }
                if i >= len(slice) {
+                       // This is a slice that we only partially allocated.
                        growSlice(v, &slice, length)
                }
                u := state.decodeUint()

diff --git a/src/encoding/gob/decgen.go b/src/encoding/gob/decgen.go
index e40816eb869ba92af55dac5da521bc5579f98a39..27a30eaf61abd795f9ccaf32103e4bb0634b98d2 100644 (file)
--- a/src/encoding/gob/decgen.go
+++ b/src/encoding/gob/decgen.go
@@ -180,6 +180,7 @@ func main() {
                fmt.Fprintf(&b, arrayHelper, t.lower, t.upper)
                fmt.Fprintf(&b, sliceHelper, t.lower, t.upper, t.decoder)
        }
+       fmt.Fprintf(&b, trailer)
        source, err := format.Source(b.Bytes())
        if err != nil {
                log.Fatal("source format error:", err)
@@ -236,8 +237,29 @@ func dec%[2]sSlice(state *decoderState, v reflect.Value, length int, ovfl error)
                if state.b.Len() == 0 {
                        errorf("decoding %[1]s array or slice: length exceeds input size (%%d elements)", length)
                }
+               if i >= len(slice) {
+                       // This is a slice that we only partially allocated.
+                       growSlice(v, &slice, length)
+               }
                %[3]s
        }
        return true
 }
 `
+
+const trailer = `
+// growSlice is called for a slice that we only partially allocated,
+// to grow it up to length.
+func growSlice[E any](v reflect.Value, ps *[]E, length int) {
+       var zero E
+       s := *ps
+       s = append(s, zero)
+       cp := cap(s)
+       if cp > length {
+               cp = length
+       }
+       s = s[:cp]
+       v.Set(reflect.ValueOf(s))
+       *ps = s
+}
+`