From: Alan Modra <amodra@gmail.com>
To: Fangrui Song <i@maskray.me>
Cc: binutils@sourceware.org
Subject: Re: Support objcopy changing compression to or from zstd
Date: Thu, 6 Oct 2022 07:34:16 +1030 [thread overview]
Message-ID: <Yz3xUEa/glumhprz@squeak.grove.modra.org> (raw)
In-Reply-To: <20221004220134.ifx4i33v2obhzitr@gmail.com>
On Tue, Oct 04, 2022 at 03:01:34PM -0700, Fangrui Song wrote:
> On 2022-10-04, Alan Modra via Binutils wrote:
> > Commit 2cac01e3ffff lacked support for objcopy changing compression
> > style. Add that support, which meant a rewrite of
> > bfd_compress_section_contents. In the process I've fixed some memory
> > leaks.
>
> For objcopy --compress-debug-sections=zstd , I know that omitting
> recompression of zlib into zstd was intentional.
>
> --compress-debug-sections=zstd does not specify what to do when a section is
> compressed, so both (a)
> do nothing (b) re-compression with zstd are fine but I think
> avoiding recompression can avoid some complexity...
>
> If a .o is compressed with zlib level 5, should --compress-debug-sections=zlib
> re-compress it or leave it as-is?
>
> At any rate, I think the objcopy --compress-debug-sections=zstd
> behavior with zlib compressed sections is mostly not interesting to a
> user.
I could have lived with objcopy --compress-debug-sections=zstd doing
nothing on already compressed sections. After all, users could change
compression schemes by a two step process, first objcopy
--decompress-debug-sections then compress with the desired scheme.
However, I discovered that objcopy --compress-debug-sections=zstd
on a zlib-gnu compressed file copied the zlib data and tacked on a
header specifying zstd. Which of course then causes errors on
attempted decompression. That needed fixing regardless of what anyone
thinks objcopy --compress-debug-sections=zstd should do with already
compressed debug sections.
--
Alan Modra
Australia Development Lab, IBM
prev parent reply other threads:[~2022-10-05 21:04 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-04 8:13 Alan Modra
2022-10-04 22:01 ` Fangrui Song
2022-10-05 6:02 ` Jan Beulich
2022-10-05 21:04 ` Alan Modra [this message]
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