[RFA] ignore PYTHONHOME environment variable.

[Jan Kratochvil]

On Tue, 14 Dec 2010 11:33:05 +0100, Joel Brobecker wrote:
> What we can also do is warn users when we see that PYTHONHOME is
> defined and not GDB_PYTHON_HOME.  That way, they are not surprised
> when that happens, and they get a helpful indication of how to
> remedy the problem.

Therefore:

if ($GDB_PYTHONHOME exists) {
  use it
} else if ($PYTHONHOME exists) {
  warn on it
  ignore it
  pass it to spawned debuggees
} else {
  let Python use it's defaults
}

That "ignore it" part may be difficult as despite Py_SetPythonHome overrides
$PYTHONHOME if !defined WITH_PYTHON_PATH we do not know which string to use
for Py_SetPythonHome to override it.  So maybe to use unsetenv before
Py_Initialize and setenv the saved string back afterwards.

Also I believe it should apply to any environment starting with PYTHON* as
besides
	$ PYTHONHOME=/foo ./gdb
	ImportError: No module named site

it affects also at least
	$ echo foo >site.py; PYTHONPATH=. ./gdb
	Traceback (most recent call last):
	  File "./site.py", line 1, in <module>
	    foo
	NameError: name 'foo' is not defined

and
	$ PYTHONVERBOSE=1 ./gdb
	# installing zipimport hook
	import zipimport # builtin
	[...]
	import gdb.command.upto # precompiled from /usr/share/gdb/python/gdb/command/upto.pyc
	GNU gdb (GDB) 7.4.50.20120512-cvs
	[...]


Thanks,
Jan