addr2line wrong search path for debug files

[Juan Navarro]

I cannot make `addr2line` to work. It does look for symbols at three (*unexisting*) paths:
/usr/bin/*.debug
/usr/bin/.debug/*.debug
/usr/lib/debug/usr/bin/*.debug

But it just seems to ignore the path where all debugging symbols are actually installed by default:
/usr/lib/debug/.build-id/

I run `addr2line` like this:
addr2line -f -C -e <PathToExecFile> <Addr>

Am I missing some configuration switch, system option, or anything similar?

------------

Now some proofs for what I'm stating.
Here, I'll be using the program `screen` as an example:

$ sudo apt-get install screen screen-dbg
$ file /usr/bin/screen
> /usr/bin/screen: setgid ELF 64-bit LSB executable, x86-64, version 1 (SYSV),
  dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, for GNU/Linux 2.6.32,
  BuildID[sha1]=e9d3cd5073daa6b7365b3787673143edeec589d3, stripped
$ dpkg -L screen-dbg
> /usr/lib/debug/.build-id/e9/d3cd5073daa6b7365b3787673143edeec589d3.debug

Here we empirically found out where the debug symbols for `screen` are:
/usr/lib/debug/.build-id/e9/d3cd5073daa6b7365b3787673143edeec589d3.debug

Now we run `strace addr2line` to see where it tries to access...

# Get any valid object address
$ objdump -T /usr/bin/screen
> 00000000006697e0

# Use the object address in addr2line
$ strace -f addr2line -f -C \
    -e /usr/bin/screen 0x00000000006697e0 2>&1 | grep debug
> open("/usr/bin/d3cd5073daa6b7365b3787673143edeec589d3.debug", O_RDONLY) = -1 ENOENT (No such file or directory)
  open("/usr/bin/.debug/d3cd5073daa6b7365b3787673143edeec589d3.debug", O_RDONLY) = -1 ENOENT (No such file or directory)
  open("/usr/lib/debug/usr/bin/d3cd5073daa6b7365b3787673143edeec589d3.debug", O_RDONLY) = -1 ENOENT (No such file or directory)

Here we see the 3 paths I mentioned earlier, but no signs of the desired one.

------------

Additional information:

- Ubuntu release

$ lsb_release -rd
> Description: Ubuntu 16.04.4 LTS
  Release: 16.04

- Package version

$ apt-cache policy binutils
> binutils:
    Installed: 2.26.1-1ubuntu1~16.04.6
    Candidate: 2.26.1-1ubuntu1~16.04.6
    Version table:
   *** 2.26.1-1ubuntu1~16.04.6 500
          500 http://archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages
          500 http://security.ubuntu.com/ubuntu xenial-security/main amd64 Packages
          100 /var/lib/dpkg/status
       2.26-8ubuntu2 500
          500 http://archive.ubuntu.com/ubuntu xenial/main amd64 Packages

- What I expected to happen

I expected that the `strace` command shown avobe would access the debug files at their actual location:
/usr/lib/debug/.build-id/e9/d3cd5073daa6b7365b3787673143edeec589d3.debug

- What happened instead

The `addr2line` program does look for the debug file at three unexisting locations:
/usr/bin/*.debug
/usr/bin/.debug/*.debug
/usr/lib/debug/usr/bin/*.debug
but it does not look for the debug file at the correct location.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.