[PATCH] D20211: [ELF] - Support of compressed debug sections creation(draft).

[Rui Ueyama via llvm-commits]

I think the most important question is whether we want to support emitting
compressed debug sections or not. Looks like reading compressed debug
sections is at least more common.

On Fri, May 13, 2016 at 6:26 AM, Rafael Espíndola <
rafael.espindola at gmail.com> wrote:

> > ruiu wrote:
> >> I think we don't have to care about this edge case. Unless you are
> compressing random bits, it usually shrink.
> > I would leave it as is. That is mentioned in docs: "The .debug_line and
> .debug_pubnames sections would be larger compressed than in their original
> uncompressed form, and have therefore been left uncompressed." (
> https://docs.oracle.com/cd/E53394_01/html/E54813/section_compression.html#scrolltoc)
> and done both by gold/bfd and very transparent in implementation.
> > In addition I think that if feature is used then motivation and expected
> result is to consume less space, I do not think it is acceptable to consume
> more than without it, it is confusing and opposite to its description.
>
>
> I think we can start without this and see how many case we hit in the
> field when it gets bigger.
>
> > ruiu wrote:
> >> Why we have two types of headers? If one is obsolete, we probably don't
> want to implement it.
> > There are 2 different approaches used (
> https://docs.oracle.com/cd/E53394_01/html/E54813/section_compression.html
> ):
> > 1) gnu-style renames sections to ".z*[NAME]" and do not uses
> SHF_COMPRESSED.
> > 2) zlib style. Sections have SHF_COMPRESSED flag and are not renamed.
> >
> > "Unless there is a specific requirement to use the zlib-gnu style, the
> more general default zlib style is recommended." says
> https://docs.oracle.com/cd/E53394_01/html/E54813/man-cds.html, but it is
> not mentioned if that depricated or something.
> > Not supporting of zlib-gnu style would make implementation a bit cleaner.
> >
> > It is not hard to support both though.
>
> Lets please start without support of the gnu style.
>
> Cheers,
> Rafael
>
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