Features/DebugInfoRevamp

= DebugInfo Revamp =

Summary
A revamp of the debuginfo rpm generation scheme exploiting new tools for DWARF compression.

Owner

 * Name: Roland McGrath
 * email: roland@redhat.com

Current status

 * Targeted release: Fedora 13
 * Last updated: 2009-06-09
 * Percentage of completion: 1%

Detailed Description
New work in elfutils will provide facilities for DWARF compression. The conventions for finding separate debuginfo files might be enhanced or rejiggered in tools like gdb and systemtap. The rpmbuild macros and scripts for generating debuginfo packages will be rewritten. These are expected to make the debuginfo rpms much smaller.

Possibly the standard will change to split debuginfo packages into debuginfo proper (/usr/lib/debug files) and sources (/usr/src/debug files) as separate subpackages.

Benefit to Fedora
Much smaller debuginfo rpms, quicker to download, smaller to host/mirror, etc.

Scope
elfutils team has to write the DWARF compression tools (will also replace rpm's debugedit), come up with debuginfo convention changes.

elfutils team + rpm/redhat-rpm-config maintainers have to decide about subpackage conventions and implement new macros/script to replace rpmbuild find-debuginfo.sh magic.

Either gdb team has to adapt it to new conventions, or DWARF tool + rpm deployment plan could include exploding in %post to current layout.

If rpm subpackage convention changes, possibly rel-eng needs to adjust mash for new naming convention and multiple debuginfo-related rpms per package.

How To Test
The elfutils team is set up for mass-testing against all the existing debuginfo rpm ELF files and will use that to test the DWARF transformation tools. https://fedorahosted.org/elfutils/wiki/DebugInfoTesting

When https://fedorahosted.org/elfutils/wiki/RpmDebugInfo work is complete, we should do mass rebuild tests outside the buildsystem to rebuild all of rawhide with the new toolset. We can then unpack all that data and run format tests against it.

Maybe do this twice, once first with the new rpmbuild helpers hacked to do dwarflint+pack+unpack+dwarflint+pack.

User Experience

 * Quicker to download and install debuginfo rpms.

Dependencies

 * elfutils work.
 * Might like a mass rebuild to get all new debuginfo rpms for the release.

Contingency Plan
Possibilities:
 * We can punt the whole thing.
 * We can do it but skip the mass rebuild.
 * We can punt adapting gdb et al if we do a deployment scheme that explodes to compatible old data in %post.

Documentation

 * https://fedorahosted.org/elfutils/wiki/RpmDebugInfo

Release Notes

 * FIXME: Should have some notes about conventions and tools when decided.

Comments and Discussion

 * See Talk:Features/DebugInfoRevamp