New submission from STINNER Victor: I recently added new functions to call functions in C, especially _PyObject_FastCallDict(). I started with the C int type for the number of positional arguments: "int nargs".
But slowly, when I started to patch code to use _PyObject_FastCallDict(), I used more and more Py_ssize_t variables for the number of arguments, variable downcasted to int to call _PyObject_FastCallDict(). It is similar to the old issue #18295. I propose to avoid any risk of integer overflow by using Py_ssize_t everywhere. It *might* produce more efficient machine code, since "i++" may require extra code to handle overflow when the int rather is used. But I'm not sure that Py_ssize_t is better, especially when -fwrapv option of the GCC compiler is used. Attached patch implements this idea. The patch also uses Py_ssize_t for some BUILD_xxx opcodes like BUILD_LIST_UNPACK. The change is not directly related. I wrote it in the hope that machine code could be more efficient, and avoid having to ask myself if types could overflow or not. ---------- files: Py_ssize_t.patch keywords: patch messages: 273549 nosy: haypo, scoder, serhiy.storchaka priority: normal severity: normal status: open title: C function calls: use Py_ssize_t rather than C int for number of arguments versions: Python 3.6 Added file: http://bugs.python.org/file44209/Py_ssize_t.patch _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue27848> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
