On Wed, Aug 20, 2025 at 11:38 PM Jan Beulich <[email protected]> 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). > > Jan
Is there an !<arch64>\n extension? I can't find !<arch64>\n in binutils, libarchive, FreeBSD's elftoolchain, or LLVM. AIX has a big archive extension that supports a larger size field, but we likely don't want to use an AIX extension. The size limit stems from the 10-byte decimal size field in the header and the symbol table offset. The /SYM64/ extension supports 64-bit symbol table offsets, and the 10-byte decimal size field in the header could be easily expanded (for parser, bfd/archive.c:538 ` scan = sscanf (hdr.ar_size, "%" SCNu64, &parsed_size);` alreads supports larger size IIRC) ( Regarding /SYM64/: I'd argue that the archive symbol table is largely unnecessary. mold and lld's ELF port completely ignore the archive symbol table. https://maskray.me/blog/2022-01-16-archives-and-start-lib > With a lower ratio, I have measured 1.01x when linking Clang. With my > experience, for projects large enough that the performance matters, the > archive utilization ratio is typically high. So I would say the archive > symbol table is nearly useless. )
