postfix-dbgsym package has empty .debug files; debian/rules dh_strip confusion

[Free Yorp]

1) The release of Ubuntu you are using, via 'lsb_release -rd' or System -> About Ubuntu
# lsb_release -rd
Description: Ubuntu 18.04.1 LTS
Release: 18.04

2) The version of the package you are using, via 'apt-cache policy pkgname' or by checking in Software Center
# apt-cache policy postfix
postfix:
  Installed: 3.3.0-1ubuntu0.2
  Candidate: 3.3.0-1ubuntu0.2
  Version table:
 *** 3.3.0-1ubuntu0.2 500
        500 http://azure.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     3.3.0-1 500
        500 http://azure.archive.ubuntu.com/ubuntu bionic/main amd64 Packages
# apt-cache policy postfix-dbgsym
postfix-dbgsym:
  Installed: 3.3.0-1ubuntu0.2
  Candidate: 3.3.0-1ubuntu0.2
  Version table:
 *** 3.3.0-1ubuntu0.2 500
        500 http://ddebs.ubuntu.com bionic-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     3.3.0-1 500
        500 http://ddebs.ubuntu.com bionic/main amd64 Packages

3) What you expected to happen

Installing postfix-dbgsym and attaching gdb to postfix loads a debugging symbol file and debugging symbols are found from it

4) What happened instead

Installing postfix-dbgsym and attaching gdb to postfix loads a debugging symbol file but debugging symbols are not found from it

I followed the instructions at https://wiki.ubuntu.com/Debug%20Symbol%20Packages and installed postfix-dbgsym.

However, when I try to attach gdb with gdb -p <pid>, I get:

'Reading symbols from /usr/lib/postfix/sbin/master...Reading symbols from /usr/lib/debug/.build-id/e0/c259ef26eda076310a6dd3eccb419ce8eb1c50.debug...(no debugging symbols found)...done.'

The .debug file in question does exist on the filesystem, and a quick dpkg -S shows that it was provided by the postfix-dbgsym package. All packages are up to date up to bionic-updates, and no processes on the system are running on outdated libraries (searching lsof for DEL).

Running objdump -g on /usr/lib/debug/.build-id/e0/c259ef26eda076310a6dd3eccb419ce8eb1c50.debug merely prints:

/usr/lib/debug/.build-id/e0/c259ef26eda076310a6dd3eccb419ce8eb1c50.debug: file format elf64-x86-64

Contents of the .eh_frame section:

00000000 ZERO terminator

The size of this .debug file is 14K; compare to the .debug file for libpthread.so.0, which was 2.3M and does provide quite a lot of output with objdump -g.

I'm struggling to get through the debian/rules file for postfix, but I can see that:
 - STRIP=y gets set depending on a test, and dh_strip -a runs if $(STRIP) is *empty* (see: [ -n "$(STRIP)" ] || dh_strip -a ).
 - The same test structure gets used for checking nostrip in args then setting STRIP=y, and for checking debug in args then setting DEBUG += -g. If said test means something like `word not in args`, then the DEBUG += -g seems like it's wrong; if it instead ends up meaning something like `word in args`, then the STRIP=y seems like it's wrong?

Manually forcing DEBUG to -g and STRIP to "" produces a set of packages with stripped binaries.
Manually forcing DEBUG to -g and STRIP to n gets me a set of packages with binaries including debugging info, which was enough to let me work around the problem.

I believe there is at least *something* wrong in the postfix/debian/rules file, but I'm not yet sure what a complete listing would be exactly, or even if it's the root cause, so to speak.

[Scott Kitterman (kitterman)]

This is fixed in 3.3.2-1, which is in disco.

Scott K

[Karl Stenerud (kstenerud)]

Confirmed this is an issue in bionic and cosmic, and is working in disco.