diff --git a/src/image/gif/reader.go b/src/image/gif/reader.go index cf5af210a6..a1da69780c 100644 --- a/src/image/gif/reader.go +++ b/src/image/gif/reader.go @@ -202,9 +202,18 @@ func (d *decoder) decode(r io.Reader, configOnly bool) error { } return errNotEnough } - // Both lzwr and br should be exhausted. Reading from them - // should yield (0, io.EOF). - if n, err := lzwr.Read(d.tmp[:1]); n != 0 || err != io.EOF { + // Both lzwr and br should be exhausted. Reading from them should + // yield (0, io.EOF). + // + // The spec (Appendix F - Compression), says that "An End of + // Information code... must be the last code output by the encoder + // for an image". In practice, though, giflib (a widely used C + // library) does not enforce this, so we also accept lzwr returning + // io.ErrUnexpectedEOF (meaning that the encoded stream hit io.EOF + // before the LZW decoder saw an explict end code), provided that + // the io.ReadFull call above successfully read len(m.Pix) bytes. + // See http://golang.org/issue/9856 for an example GIF. + if n, err := lzwr.Read(d.tmp[:1]); n != 0 || (err != io.EOF && err != io.ErrUnexpectedEOF) { if err != nil { return err }