Re: [RFA] ignore PYTHONHOME environment variable.

[Joel Brobecker <brobecker@adacore.com>]

> <jan.kratochvil@redhat.com> wrote:
> > But PYTHONHOME=$HOME for some user overrides of system Python would
> > no longer work.  What would $PYTHONHOME otherwise be useful for?
> 
> OTOH what if one wanted to debug a python with a different PYTHONHOME?
> GDB_PYTHONHOME?  [not my idea, but seems reasonable]

I think you indeed need something like that. I don't think we can trust
PYTHONHOME, because it might point to something that's incompatible.

GDB_PYTHONHOME is something that got suggested by at least 2 people
(someone at AdaCore also suggested it a while back).  I have to wonder,
though, why you would want to run GDB with a different version of Python
than then one used to build GDB with.  If you want to use your own
scripts, you can use the PYTHONPATH.

Still, we can add that too, something like that:

  #ifdef WITH_PYTHON_PATH
    if "GDB_PYTHONHOME" is defined
      Py_SetPythonHome (getenv ("GDB_PYTHONHOME"));
    else
      /* We override any value that the PYTHONHOME might have, as we want
         to make sure that we use the Python library that comes with GDB.  */
      Py_SetPythonHome (ldirname (python_libdir));
  #endif

But I think I would prefer something like this:

  if "GDB_PYTHONHOME" is defined
    Py_SetPythonHome (getenv ("GDB_PYTHONHOME"));
  #ifdef WITH_PYTHON_PATH
    else
      /* We override any value that the PYTHONHOME might have, as we want
         to make sure that we use the Python library that comes with GDB.  */
      Py_SetPythonHome (ldirname (python_libdir));
  #endif

The latter makes GDB_PYTHONHOME always active, regardless of how
GDB was linked against Python.

-- 
Joel