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

Rafael EspĂ­ndola via llvm-commits llvm-commits at lists.llvm.org
Fri May 13 06:26:15 PDT 2016

> 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 If one is obsolete, we probably don't want to implement it.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.


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