[Bug 1879092] Autopkgtest regression report (glibc/2.31-0ubuntu9.1)

[Ubuntu SRU Bot]

All autopkgtests for the newly accepted glibc (2.31-0ubuntu9.1) for focal have finished running.
The following regressions have been reported in tests triggered by the package:

prometheus-blackbox-exporter/0.13.0+ds-2 (armhf, amd64, ppc64el, s390x, arm64)
prometheus-pushgateway/1.0.0+ds-1 (armhf, amd64, ppc64el, s390x, arm64)
systemd/245.4-4ubuntu3.2 (s390x, amd64, ppc64el)
gfs2-utils/unknown (amd64)
hugo/0.68.3-1 (armhf, amd64, ppc64el, s390x, arm64)
grubzfs-testsuite/0.4.10 (amd64)
glibc/2.31-0ubuntu9.1 (armhf)
badger/2.0.1-3 (armhf, amd64, ppc64el, s390x, arm64)
resource-agents/1:4.5.0-2ubuntu2 (armhf)
etcd/3.2.26+dfsg-6 (amd64, ppc64el)
postgresql-multicorn/1.3.4-31-g9ff7875-3 (armhf, amd64, ppc64el, s390x)
gfs2-utils/3.2.0-3 (ppc64el, s390x, arm64)
scipy/1.3.3-3build1 (ppc64el)


Please visit the excuses page listed below and investigate the failures, proceeding afterwards as per the StableReleaseUpdates policy regarding autopkgtest regressions [1].

https://people.canonical.com/~ubuntu-archive/proposed-
migration/focal/update_excuses.html#glibc

[1] https://wiki.ubuntu.com/StableReleaseUpdates#Autopkgtest_Regressions

Thank you!

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https://bugs.launchpad.net/bugs/1879092

Title:
  gfortran can't use vectorized functions.

Status in gcc-10 package in Ubuntu:
  New
Status in glibc package in Ubuntu:
  Fix Released
Status in gcc-10 source package in Focal:
  New
Status in glibc source package in Focal:
  Fix Committed
Status in gcc-10 source package in Groovy:
  New
Status in glibc source package in Groovy:
  Fix Released

Bug description:
  [Impact]

  After ubuntu-glibc maintainers changed "math-vector-fortran.h" install
  directory (LP#1861353), gfortran can no longer use it.

  [Test Case]

  This the old (good) behavior Ubuntu 19.10 gcc-9.2.1 glibc 2.30
  $ gfortran -O3 -mavx2 vect_test.f90 -o test.x
  $ nm ./test.x | grep sin
      U _ZGVdN4v_sin@@GLIBC_2.22
      U _ZGVdN8v_sinf@@GLIBC_2.22

  After that change : Ubuntu 20.04 gcc-9.3.0 glibc 2.31
  $ gfortran -O3 -mavx2 vect_test.f90 -o test.x
  $ nm ./test.x | grep sin
      U sin@@GLIBC_2.2.5
      U sinf@@GLIBC_2.2.5

  $ cat vect_test.f90
  program test_vect
    implicit none
    integer, parameter :: n = 64*1024**2
    integer :: i
    integer(8) :: t1, t2, t0
    real(8) :: tic
    !
    real, allocatable :: a32(:), b32(:)
    real(8), allocatable :: a64(:), b64(:)
    !
    allocate( a32(n), a64(n))
    allocate( b32(n), b64(n))
    !
    call random_number(a32 )
    call random_number(a64 )
    !
    call system_clock(t0, tic)
    !
    do i = 1, n
      b32(i) = sin(a32(i))
    end do
    !
    call system_clock(t1)
    print*, (t1-t0)/tic
    !
    do i = 1, n
      b64(i) = sin(a64(i))
    end do
    !
    call system_clock(t2)
    print*, (t2-t1)/tic
    !
  end program test_vect

  Verbose:

  Ubuntu 19.10
  $ gfortran -O3 -mavx2 -v vect_test.f90 -o test.x
  ...
  /usr/lib/gcc/x86_64-linux-gnu/9/f951 vect_test.f90 -quiet -dumpbase vect_test.f90 -mavx2 -mtune=generic -march=x86-64 -auxbase vect_test -O3 -version -fintrinsic-modules-path /usr/lib/gcc/x86_64-linux-gnu/9/finclude -fpre-include=/usr/include/finclude/math-vector-fortran.h -o /tmp/cc2E2K8s.s
  ...

  Ubuntu 20.04
  $ gfortran -O3 -mavx2 -v vect_test.f90 -o test.x
  ...
  /usr/lib/gcc/x86_64-linux-gnu/9/f951 vect_test.f90 -quiet -dumpbase vect_test.f90 -mavx2 -mtune=generic -march=x86-64 -auxbase vect_test -O3 -version -fintrinsic-modules-path /usr/lib/gcc/x86_64-linux-gnu/9/finclude -o /tmp/cc4swJwz.s
  ...

  [Other Info]

  As you can see gfortran is not preincluding "math-vector-fortran.h" file on Ubuntu 20.04.
  A workaround is to copy "math-vector-fortran.h" to /usr/include/finclude (which is empty!).

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