[Python-Dev] C99

[Martin Panter]

On 4 June 2016 at 06:11, Benjamin Peterson <benjamin at python.org> wrote:
> PEP 7 requires CPython to use C code conforming to the venerable C89
> standard. Traditionally, we've been stuck with C89 due to poor C support
> in MSVC. However, MSVC 2013 and 2015 implement the key features of C99.
> C99 does not offer anything earth-shattering; here are the features I
> think we'd find most interesting:
> - Variable declarations can be on any line: removes possibly the most
> annoying limitation of C89.
> - Inline functions: We can make Py_DECREF and Py_INCREF inline functions
> rather than unpleasant macros.
> - C++-style line comments: Not an killer feature but commonly used.
> - Booleans

My most-missed C99 feature would be designated initializers. Does MSVC
support them? It might allow you to do away with those giant pasted
slot tables, and just write the slots you need:

PyTypeObject PyUnicodeIter_Type = {
    PyVarObject_HEAD_INIT(&PyType_Type, 0)
    .tp_name = "str_iterator",
    .tp_basicsize = sizeof(unicodeiterobject),
    .tp_dealloc = unicodeiter_dealloc,
    .tp_getattro = PyObject_GenericGetAttr,
    .tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,
    .tp_traverse = unicodeiter_traverse,
    .tp_iter = PyObject_SelfIter,
    .tp_iternext = unicodeiter_next,
    .tp_methods = unicodeiter_methods,
};

> So, what say you to updating PEP 7 to allow C99 features for Python 3.6
> (in so much as GCC and MSVC support them)?

Sounds good for features that are well-supported by compilers that
people use. (Are there other compilers used than just GCC and MSVC?)