[Bug 1818918] Re: gdb doesn't search in debug-file-directory for .gnu_debugaltlink

[Benjamin Drung]

The apport workaround is ugly in two ways: First it is a workaround and
second it needs root permission:

```
Traceback (most recent call last):
  File "/home/ubuntu/apport/bin/apport-retrace", line 688, in <module>
    main()
  File "/home/ubuntu/apport/bin/apport-retrace", line 441, in main
    os.mkdir("/usr/lib/debug/.dwz")
FileNotFoundError: [Errno 2] No such file or directory: '/usr/lib/debug/.dwz'
```

So can we please backport the gdb fix to 18.04 and 20.04 to be able to
drop this workaround?

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Title:
  gdb doesn't search in debug-file-directory for .gnu_debugaltlink

Status in Apport:
  Fix Released
Status in apport package in Ubuntu:
  Fix Released
Status in gdb package in Ubuntu:
  Fix Released

Bug description:
  As far as I can tell gdb version 8.2.90 isn't searching the debug-
  file-directory, which I set, for the '.gnu_debugaltlink' which is in
  the debug symbols. Here's the error I'm seeing:

  Type "apropos word" to search for commands related to "word".
  Reading symbols from /srv/vms/apport-sandbox-dir/Ubuntu 19.04/amd64/report-sandbox//usr/bin/gnome-calculator...
  Reading symbols from /srv/vms/apport-sandbox-dir/Ubuntu 19.04/amd64/report-sandbox/usr/lib/debug/.build-id/95/59c4c5ee30eb66d47bb9bd64784a69c9a6de6b.debug...
  could not find '.gnu_debugaltlink' file for /srv/vms/apport-sandbox-dir/Ubuntu 19.04/amd64/report-sandbox/usr/lib/debug/.build-id/95/59c4c5ee30eb66d47bb9bd64784a69c9a6de6b.debug
  (No debugging symbols found in /srv/vms/apport-sandbox-dir/Ubuntu 19.04/amd64/report-sandbox/usr/lib/debug/.build-id/95/59c4c5ee30eb66d47bb9bd64784a69c9a6de6b.debug)

  Here's part of an strace of what's going on behind the scenes:

  lstat("/srv/vms/apport-sandbox-dir/Ubuntu 19.04/amd64/report-sandbox/usr/lib/debug/.build-id/95/59c4c5ee30eb66d47bb9bd64784a69c9a6de6b.debug", {st_mode=S_IFREG|0644, st_size=839744, ...}) = 0 
  openat(AT_FDCWD, "/usr/lib/debug/.dwz/x86_64-linux-gnu/gnome-calculator.debug", O_RDONLY|O_CLOEXEC) = -1 ENOENT (No such file or directory)

  This is the only time "/usr/lib/debug" is searched, generally
  "/srv/vms/apport-sandbox-dir/Ubuntu 19.04/amd64/report-
  sandbox/usr/lib/debug/" is used. I'll attach the full strace though.

  For completeness here's the gdb command I'm using:

  Calling gdb command: '/srv/vms/apport-sandbox-dir/Ubuntu
  19.04/amd64/report-sandbox/lib/x86_64-linux-gnu/ld-linux-x86-64.so.2'
  '/srv/vms/apport-sandbox-dir/Ubuntu 19.04/amd64/report-
  sandbox/usr/bin/gdb' --ex 'set debug-file-directory /srv/vms/apport-
  sandbox-dir/Ubuntu 19.04/amd64/report-sandbox/usr/lib/debug' --ex 'set
  solib-absolute-prefix /srv/vms/apport-sandbox-dir/Ubuntu
  19.04/amd64/report-sandbox' --ex 'add-auto-load-safe-path
  /srv/vms/apport-sandbox-dir/Ubuntu 19.04/amd64/report-sandbox' --ex
  'set solib-search-path /srv/vms/apport-sandbox-dir/Ubuntu
  19.04/amd64/report-sandbox/lib/x86_64-linux-gnu' --ex 'set data-
  directory /srv/vms/apport-sandbox-dir/Ubuntu 19.04/amd64/report-
  sandbox/usr/share/gdb' --ex 'file "/srv/vms/apport-sandbox-dir/Ubuntu
  19.04/amd64/report-sandbox//usr/bin/gnome-calculator"' --ex 'core-file
  /tmp/apport_core_1b6dn6np'

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