[PATCH STABLE] parsers: do not cache RevlogError type (issue4451)

[Yuya Nishihara]

On Fri, 12 Jun 2015 14:45:25 -0700, Gregory Szorc wrote:
> # HG changeset patch
> # User Gregory Szorc <gregory.szorc at gmail.com>
> # Date 1434145439 25200
> #      Fri Jun 12 14:43:59 2015 -0700
> # Branch stable
> # Node ID 6c0eef5e16a598e60623afcd8db0fdf7205bed1c
> # Parent  7298da81f5a9f64ebbdef2b2195585a65da0f99e
> parsers: do not cache RevlogError type (issue4451)

> +	mod = PyImport_ImportModule("mercurial.error");
> +	if (mod == NULL) {
> +		goto cleanup;
>  	}
>  
> -	errobj = PyObject_CallFunction(errclass, NULL);
> -	if (errobj == NULL)
> -		return NULL;
> -	PyErr_SetObject(errclass, errobj);
> -	return errobj;
> +	dict = PyModule_GetDict(mod);
> +	if (dict == NULL) {
> +		goto cleanup;
> +	}
> +	Py_INCREF(dict);
>  
> -classfail:
> +	errclass = PyDict_GetItemString(dict, "RevlogError");
> +	if (errclass == NULL) {
> +		PyErr_SetString(PyExc_SystemError,
> +				"could not find RevlogError");
> +		goto cleanup;
> +	}
> +
> +	/* value of exception is ignored by callers */
> +	PyErr_SetString(errclass, "RevlogError");
> +
> +cleanup:
> +	Py_XDECREF(dict);
>  	Py_XDECREF(mod);

I'm not sure if we need to incref/decref the module dict, but if we want to
make sure the errclass is alive in this function, we could instead do

  errclass = PyObject_GetAttrString(mod, "RevlogError");
  ...
  Py_XDECREF(errclass);

https://docs.python.org/2/faq/extending.html#how-do-i-access-a-module-written-in-python-from-c

That said, I don't think it won't be suitable for stable.