From 6f44cc88f5f94253096ceed16b8e0fdb117cdd06 Mon Sep 17 00:00:00 2001 From: Jonathan Amsterdam Date: Sat, 3 Feb 2024 11:48:50 -0500 Subject: [PATCH] archive/zip: reduce memory held by Writer.Copy Make a copy of the argument File's FileHeader, and pass a pointer to the copy to CreateRaw. Passing the pointer directly causes the entire `File` to be referenced by the receiver. The `File` includes a reference to the `ReaderAt` underlying the `Reader`, so all its memory, which may be the entire contents of the archive, is prevented from being garbage-collected. Also, explain the issue in the doc comment for CreateRaw. We cannot change its behavior because someone may depend on the preserving the identity of its argument pointer. For #65499. Change-Id: Ieb4963a0ea30539d597547d3511accbd8c6b5c5a Reviewed-on: https://go-review.googlesource.com/c/go/+/560238 LUCI-TryBot-Result: Go LUCI Reviewed-by: Damien Neil --- src/archive/zip/writer.go | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/src/archive/zip/writer.go b/src/archive/zip/writer.go index e33df2431c..9e2dcff713 100644 --- a/src/archive/zip/writer.go +++ b/src/archive/zip/writer.go @@ -433,6 +433,10 @@ func writeHeader(w io.Writer, h *header) error { // [Writer.CreateHeader], [Writer.CreateRaw], or [Writer.Close]. // // In contrast to [Writer.CreateHeader], the bytes passed to Writer are not compressed. +// +// CreateRaw's argument is stored in w. If the argument is a pointer to the embedded +// [FileHeader] in a [File] obtained from a [Reader] created from in-memory data, +// then w will refer to all of that memory. func (w *Writer) CreateRaw(fh *FileHeader) (io.Writer, error) { if err := w.prepare(fh); err != nil { return nil, err @@ -471,7 +475,10 @@ func (w *Writer) Copy(f *File) error { if err != nil { return err } - fw, err := w.CreateRaw(&f.FileHeader) + // Copy the FileHeader so w doesn't store a pointer to the data + // of f's entire archive. See #65499. + fh := f.FileHeader + fw, err := w.CreateRaw(&fh) if err != nil { return err } -- 2.48.1