Re: Extending ar format to support large member sizes
On 21.08.2025 10:01, Fangrui Song wrote:
> On Wed, Aug 20, 2025 at 11:38 PM Jan Beulich <jbeulich@suse.com> wrote:
>>
>> On 21.08.2025 04:50, Guillem Jover wrote:
>>> As you probably know the deb 2.x packaging format [D] is based on an
>>> ar container, with tar members for its format definition, control
>>> metadata and filesystem data payloads (among others).
>>>
>>> A problem that has been known for a while now [S], is that the ar format
>>> has a file size limit, which means the deb format is thus limited to
>>> filesystem payloads (usually compressed) of at most around 9536.74 MiB.
>>>
>>> This is starting to become an issue, and it's something that has been
>>> bothering me for a bit, because support for a new deb format should be
>>> ready way before we need it, as older tools should ideally be able to
>>> handle it. And there are multiple tools involved that will need to be
>>> updated [T].
>>
>> Hasn't there been an extension to cover that for many years, using "!<arch64>\n"
>> as file signature? I do not know, however, for well formalized that extension is,
>> which solely differs from traditional archives by having a 20-byte size field (in
>> place of the 10-byte one).
>
> Is there an !<arch64>\n extension?
15 or more years ago, when I came across this, I didn't write down its
origin. It may be a Windows world extension.
> I can't find !<arch64>\n in
> binutils, libarchive, FreeBSD's elftoolchain, or LLVM.
Right, that's what may need adding there. Or whatever else extension we
may want to use.
Jan
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