release-upgrade allowed an upgrade from 18.04 to 20.04 although a strange version of gcc-10-base was installed

[Muhammad Usman Sarwar]

lsb_release -rd
Description: Ubuntu 20.04 LTS
Release: 20.04

$apt-cache policy gcc-10-base
gcc-10-base:
  Installed: 10-20200416-0ubuntu1~18.04
  Candidate: 10-20200416-0ubuntu1~18.04
  Version table:
 *** 10-20200416-0ubuntu1~18.04 100
        100 /var/lib/dpkg/status
     10-20200411-0ubuntu1 500
        500 http://repo.isra.edu.pk/ubuntu focal/main amd64 Packages

I have upgrade from ubuntu 18.04. most libraries are not upgraded i.e GCC-10-base. multiple libraries are not installed and when I try to install them. error will generate that GCC-10-base 2020-04 required but 18.04 is installed. I have remove all absolute packages and replace all packages. when I try to remove GCC-10-base or reinstall then the error is generated. multiple packages have broken during up-gradation.

``` reading package lists... Done
Building dependency tree
Reading state information... Done
Reinstallation of gcc-10-base is not possible, it cannot be downloaded.
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.```

```
The following packages have unmet dependencies:
 libfcl-dev : Depends: libflann-dev but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

```
I have continued to add missing packages in the list. but at the end following the problem raises.

```
sudo apt install gcc-10-base libgcc-10-dev gcc-10 libgfortran-10-dev libgfortran5 gfortran-10 libhdf5-openmpi-103 libopenmpi-dev libopenmpi-dev libhdf5-openmpi-dev mpi-default-dev libhdf5-mpi-dev libflann-dev libfcl-dev
Reading package lists... Done
Building dependency tree
Reading state information... Done
gcc-10-base is already the newest version (10-20200416-0ubuntu1~18.04).
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 gcc-10 : Depends: cpp-10 (= 10-20200411-0ubuntu1) but it is not going to be installed
          Depends: gcc-10-base (= 10-20200411-0ubuntu1) but 10-20200416-0ubuntu1~18.04 is to be installed
 gfortran-10 : Depends: gcc-10-base (= 10-20200411-0ubuntu1) but 10-20200416-0ubuntu1~18.04 is to be installed
 libgcc-10-dev : Depends: gcc-10-base (= 10-20200411-0ubuntu1) but 10-20200416-0ubuntu1~18.04 is to be installed
                 Depends: libasan6 (>= 10-20200411-0ubuntu1) but it is not going to be installed
 libgfortran-10-dev : Depends: gcc-10-base (= 10-20200411-0ubuntu1) but 10-20200416-0ubuntu1~18.04 is to be installed
 libgfortran5 : Depends: gcc-10-base (= 10-20200411-0ubuntu1) but 10-20200416-0ubuntu1~18.04 is to be installed
E: Unable to correct problems, you have held broken packages.
```
I am going to remove but ubuntu say
```
sudo apt remove gcc-10-base
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 libgcc-s1 : Depends: gcc-10-base (= 10-20200416-0ubuntu1~18.04) but it is not going to be installed
 libxml2 : Depends: libicu66 (>= 66.1-1~) but it is not going to be installed
E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.

$sudo apt install doxygen
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following additional packages will be installed:
  libxapian30
Suggested packages:
  doxygen-latex doxygen-doc doxygen-gui graphviz xapian-tools
The following NEW packages will be installed:
  doxygen libxapian30
0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded.
Need to get 661 kB/10.3 MB of archives.
After this operation, 46.1 MB of additional disk space will be used.
Do you want to continue? [Y/n] y
Err:1 http://repo.isra.edu.pk/ubuntu focal/universe amd64 libxapian30 amd64 1.4.14-2
  404 Not Found [IP: 121.52.154.237 80]
E: Failed to fetch http://repo.isra.edu.pk/ubuntu/pool/universe/x/xapian-core/libxapian30_1.4.14-2_amd64.deb 404 Not Found [IP: 121.52.154.237 80]
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?

```

I expected after degradation all packages must upgrade into ubuntu 20.04.
but multiple packages have not upgraded even I have replaced all packages and remove all old and absolute packages.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubuntu-release-upgrader-core 1:20.04.18
ProcVersionSignature: Ubuntu 5.4.0-24.28-generic 5.4.30
Uname: Linux 5.4.0-24-generic x86_64
ApportVersion: 2.20.11-0ubuntu27
Architecture: amd64
CasperMD5CheckResult: skip
CrashDB: ubuntu
CurrentDesktop: ubuntu:GNOME
Date: Mon Apr 20 10:09:49 2020
InstallationDate: Installed on 2020-02-12 (67 days ago)
InstallationMedia: Ubuntu 18.04.3 LTS "Bionic Beaver" - Release amd64 (20190805)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
Symptom: release-upgrade
UpgradeStatus: Upgraded to focal on 2020-04-19 (0 days ago)
VarLogDistupgradeTermlog:

[Brian Murray (brian-murray)]

The package versions of gcc-10-base are not ones provided by the Ubuntu archive and the version that you have installed is greater than the version of the package which is in the official archive for focal. While the release upgrader probably should not have let you upgrade this is a situation you'll need to untangle yourself.

[Brian Murray (brian-murray)]

It looks like the strange version of gcc-10-base came from here:

https://launchpad.net/~ubuntu-toolchain-r/+archive/ubuntu/test

[Launchpad Janitor (janitor)]

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

[David Tolnay (dtolnay)]

I had the same issue with gcc-10-base upgrading 18.04 to 20.04 after having used the ubuntu-toolchain-r/test ppa. The following fixed it:

$ sudo apt install ppa-purge
$ sudo add-apt-repository ppa:ubuntu-toolchain-r/test
$ sudo ppa-purge -o ubuntu-toolchain-r -p test
$ sudo apt dist-upgrade
$ sudo apt autoremove

The ppa-purge automatically downgraded gcc-10-base, libatomic1, libcc1-0, libgcc-s1, libgomp1, libitm1, liblsan0, libquadmath0, libstdc++6, libtsan0 to the ones provided by focal. After that, the dist-upgrade was able to upgrade build-essential, g++, gcc.