python: Make Windows-specific code work with Python 3

  Windows workaround in python_run_simple_file() used Python 2
APIs which were removed in Python 3. This commit adds a
conditionally compiled variant that uses Python 3 APIs.

gdb/ChangeLog:

	* python/python.c (python_run_simple_file): Fix for
	Python 3.
---
 gdb/ChangeLog       |  5 +++++
 gdb/python/python.c | 13 +++++++++++--
 2 files changed, 16 insertions(+), 2 deletions(-)
  

>>>>> "Jan" == Jan Vrany <jan.vrany@fit.cvut.cz> writes:

Jan> Windows workaround in python_run_simple_file() used Python 2
Jan> APIs which were removed in Python 3. This commit adds a
Jan> conditionally compiled variant that uses Python 3 APIs.

Jan> +# ifdef IS_PY3K
Jan> +  FILE *python_file = _Py_fopen (full_path.get (), (char *) "r");

I'm a bit reluctant to rely on an undocumented API.
I'd guess from the name that this is supposed to be internal...?

Also, nothing closes this new file.

Tom
  

On Tue, 2018-10-30 at 14:08 -0600, Tom Tromey wrote:
> > > > > > "Jan" == Jan Vrany <jan.vrany@fit.cvut.cz> writes:
> 
> Jan> Windows workaround in python_run_simple_file() used Python 2
> Jan> APIs which were removed in Python 3. This commit adds a
> Jan> conditionally compiled variant that uses Python 3 APIs.
> 
> Jan> +# ifdef IS_PY3K
> Jan> +  FILE *python_file = _Py_fopen (full_path.get (), (char *) "r");
> 
> I'm a bit reluctant to rely on an undocumented API.

Me to, to be honest, but I could not find any other way...

> I'd guess from the name that this is supposed to be internal...?

...and then I actually looked at the Python header file,. The _Py_fopen()
is declared as follows (see fileutils.h).

PyAPI_FUNC(FILE*) _Py_fopen(
    const char *pathname,
    const char *mode);

Looking at pyport.h, it says:

/* Declarations for symbol visibility.

  PyAPI_FUNC(type): Declares a public Python API function and return type
  PyAPI_DATA(type): Declares public Python data and its type
  ...
*/

which made me thing using _Py_fopen() would be okish, at least for some 
time. I'm not a python hacker though.

> Also, nothing closes this new file.

Argh, good point. Will check that. Thanks!

Jan
  

> On Oct 30, 2018, at 4:28 PM, Jan Vrany <jan.vrany@fit.cvut.cz> wrote:
> 
> On Tue, 2018-10-30 at 14:08 -0600, Tom Tromey wrote:
>>>>>>> "Jan" == Jan Vrany <jan.vrany@fit.cvut.cz> writes:
>> 
>> Jan> Windows workaround in python_run_simple_file() used Python 2
>> Jan> APIs which were removed in Python 3. This commit adds a
>> Jan> conditionally compiled variant that uses Python 3 APIs.
>> 
>> Jan> +# ifdef IS_PY3K
>> Jan> +  FILE *python_file = _Py_fopen (full_path.get (), (char *) "r");
>> 
>> I'm a bit reluctant to rely on an undocumented API.
> 
> Me to, to be honest, but I could not find any other way...

I've been at the receiving end of grief for using a _Py_foo call.  It might stop working in some release and that would be a hassle.  You might ask on the Python list for advice.  Given what you're looking for there clearly has to be some approved way of doing this with just public APIs.

	paul