Commit 733ee917 authored by Rob Pike's avatar Rob Pike

encoding/gob: don't cache broken encoding engines.

Fixes a situation where a nested bad type would still
permit the outer type to install a working engine, leading
to inconsistent behavior.

Fixes #3273.

R=bsiegert, rsc
CC=golang-dev
https://golang.org/cl/6294067
parent 45969825
......@@ -704,9 +704,20 @@ func (enc *Encoder) getEncEngine(ut *userTypeInfo) *encEngine {
error_(err1)
}
if info.encoder == nil {
// mark this engine as underway before compiling to handle recursive types.
// Assign the encEngine now, so recursive types work correctly. But...
info.encoder = new(encEngine)
// ... if we fail to complete building the engine, don't cache the half-built machine.
// Doing this here means we won't cache a type that is itself OK but
// that contains a nested type that won't compile. The result is consistent
// error behavior when Encode is called multiple times on the top-level type.
ok := false
defer func() {
if !ok {
info.encoder = nil
}
}()
info.encoder = enc.compileEnc(ut)
ok = true
}
return info.encoder
}
......
......@@ -780,3 +780,36 @@ func TestNilPointerInsideInterface(t *testing.T) {
t.Fatal("expected error about nil pointer and interface, got:", errMsg)
}
}
type Bug4Public struct {
Name string
Secret Bug4Secret
}
type Bug4Secret struct {
a int // error: no exported fields.
}
// Test that a failed compilation doesn't leave around an executable encoder.
// Issue 3273.
func TestMutipleEncodingsOfBadType(t *testing.T) {
x := Bug4Public{
Name: "name",
Secret: Bug4Secret{1},
}
buf := new(bytes.Buffer)
enc := NewEncoder(buf)
err := enc.Encode(x)
if err == nil {
t.Fatal("first encoding: expected error")
}
buf.Reset()
enc = NewEncoder(buf)
err = enc.Encode(x)
if err == nil {
t.Fatal("second encoding: expected error")
}
if !strings.Contains(err.Error(), "no exported fields") {
t.Errorf("expected error about no exported fields; got %v", err)
}
}
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