Re: [PATCH] fix build failure with Python 3.7

[Sergio Durigan Junior <sergiodj@redhat.com>]

On Thursday, May 31 2018, Paul Koning wrote:

> This cures PR gdb/33470, build failure due to calling an internal 
> API in Python that changed in V3.7.  The code now uses the
> "inittab" mechanism in Python, which is the approved way to
> make compiled-in modules known to Python.
>
> Gdb starts properly and I can see the _gdb module.  On my test
> system (a Mac) it's hard to get gdb to run at all, so the
> test suite is a bit problematic.  What other tests are needed?

Thanks for the patch, Paul.  I'll run this on BuildBot and see what
comes out of it.  Meanwhile...

> 	paul
>
> gdb/ChangeLog:
>
> 2018-05-31  Paul Koning  <paul_koning@dell.com>
>
> 	PR gdb/33470

This bug number is actually from Python's bugzilla, not GDB's.  So it's
not correct to mention it here in the ChangeLog/commit message.  AFAIK,
there's no correspondent GDB bug filed for this issue.

> 	* python/python.c (do_start_initialization):
> 	Avoid call to internal Python API.
> 	(PyInit__gdb): New function.
>
> diff --git a/gdb/python/python.c b/gdb/python/python.c
> index c29e7d7a6b..89443aee25 100644
> --- a/gdb/python/python.c
> +++ b/gdb/python/python.c
> @@ -1667,6 +1667,14 @@ finalize_python (void *ignore)
>    restore_active_ext_lang (previous_active);
>  }
>  
> +#ifdef IS_PY3K
> +PyMODINIT_FUNC
> +PyInit__gdb (void)
> +{
> +  return PyModule_Create (&python_GdbModuleDef);
> +}
> +#endif

I think it's a good idea to add a comment to this function.

> +
>  static bool
>  do_start_initialization ()
>  {
> @@ -1707,6 +1715,9 @@ do_start_initialization ()
>       remain alive for the duration of the program's execution, so
>       it is not freed after this call.  */
>    Py_SetProgramName (progname_copy);
> +
> +  /* Define _gdb as a built-in module.  */
> +  PyImport_AppendInittab ("_gdb", PyInit__gdb);
>  #else
>    Py_SetProgramName (progname.release ());
>  #endif
> @@ -1716,9 +1727,7 @@ do_start_initialization ()
>    PyEval_InitThreads ();
>  
>  #ifdef IS_PY3K
> -  gdb_module = PyModule_Create (&python_GdbModuleDef);
> -  /* Add _gdb module to the list of known built-in modules.  */
> -  _PyImport_FixupBuiltin (gdb_module, "_gdb");
> +  gdb_module = PyImport_ImportModule ("_gdb");
>  #else
>    gdb_module = Py_InitModule ("_gdb", python_GdbMethods);
>  #endif

-- 
Sergio
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