[PATCH] D91028: [llvm-objcopy][NFC] replace class Buffer/MemBuffer/FileBuffer with streams.

Wed Mar 3 04:45:09 PST 2021

avl added a comment.

> Sorry, I've been unwell, and not been able to look more at this yet.

> Also, one of our downstream users has recently run into a bug which probably impacts users of raw_fd_ostream, when writing from a Windows VM to a MacOS shared directory - they encounter "bad file descriptor" errors, in a manner simialr to https://bugs.llvm.org/show_bug.cgi?id=42623. I haven't filed a bug for this yet, as we're still trying to narrow down what is likely causing the problem, but I'm about 90% certain it is a general bug in raw_fd_ostream in this situation (copying to a memory mapped file as opposed to calling ::write works). At the moment, this bug affects llvm-objcopy when copying archives, but not objects, as the two wirting paths are different. It would be a shame if we introduced the bug into more areas, and I think this change does that. Perhaps we should try fixing that problem first?

I think yes it would be better to fix the problem first. Though we need a reproducer for that problem to not wait forever...

It looks like https://bugs.llvm.org/show_bug.cgi?id=42623 is already resolved in llvm by  https://reviews.llvm.org/D81803. (But it has a problem with Windows7, which caused reverting in the rust compiler https://github.com/rust-lang/rust/issues/82677)

Please, let me known if I may help with fixing this.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D91028/new/

https://reviews.llvm.org/D91028