LaTeX: wrong internal links in pdf to captioned code-blocks when numfig is not True

[jfbu]

Describe the bug

Captioned code-blocks in distinct sections which are numbered the same confuse the internal links inside pdf output.

To Reproduce
Steps to reproduce the behavior:

Use sphinx-quickstart to create fresh project then use following index.rst file

Welcome to FOO's documentation!
===============================

Section One
-----------

This link: :ref:`last` fails to jump to last code-block in pdf output
(if ``numfig`` not set).

.. code-block:: none
   :caption: first

   a

.. code-block:: none
   :caption: second
   :name: II

   b


.. code-block:: none
   :caption: third

   c

Section Two
-----------

.. code-block:: none
   :caption: last one
   :name: last

   d

.. See also :numref:`II`.

The pdf link :ref:`last` brings us back to first code-block in first section.

Execute make latexpdf and open pdf output in some viewer. The internal hyperlinks are wrong. Also the latex log file contains following warnings:

Chapter 2.
pdfTeX warning (ext4): destination with the same identifier (name{literalblock.
1}) has been already used, duplicate ignored

Expected behavior

Internal links in pdf work.

Environment info

• Python version: 3.6.8 (CPython)
• Sphinx version: tested with v2.0.0 as well as current 3.x
• Extra tools: TeXLive 2020

Additional context
With numfig = True in conf.py, the issue does not show.