[Python-Dev] Collection of typedefs for integral types

[Tim Peters]

[Guido]
> ... (Is a summary of these [C9X] names online somewhere?)

ISO refuses to put current stds online, so I'll reword an anonymous source
(shhh!  & some of this may be a little out of date):

Exact-width typedefs:
     int8_t     int16_t     int32_t     int64_t
    uint8_t    uint16_t    uint32_t    uint64_t

    It's allowed that a given platform not define *any* of these.
    Therefore portable code can never rely on having exactly N bits
    regardless of N.

Minimum-width typedefs:
     int_least8_t   int_least16_t   int_least32_t    int_least64_t
    uint_least8_t  uint_least16_t  uint_least32_t   uint_least64_t

    *All* of these must be defined (so even teensy platforms have to
    fake at least 64 bits).

Fastest minimum-width typedefs:
     int_fast8_t    int_fast16_t    int_fast32_t    int_fast64_t
    uint_fast8_t   uint_fast16_t   uint_fast32_t   uint_fast64_t

    All of these must exist.  What's the difference between these and
    minimum-width?  For example, on a Cray J90 the least8_t will be a
    char, but since the HW supports no byte operations, the fast8_t will
    likely be 64 bits wide.

Pointer<->int casting
     intptr_t
    uintptr_t

    These are signed & unsigned int types such that a valid void* p can
    be cast to them and back again, yielding a result == p.  Very
    curiously, the last draft std I saw allowed for neither to be defined!

Fattest types
     intmax_t
    uintmax_t

    The biggest int type (note that this may be fatter than "long long"!).
    Must be defined.

Limit macros
    The names of these match the regexp (re.VERBOSE):
        U? INT (8|16|32|64) _ (MIN|MAX)
    |   U? INT_ (LEAST|FAST) (8|16|32|64) _ (MIN|MAX)
    |   INTPTR_ (MIN|MAX)
    |   UINTPTR_MAX
    |   INTMAX_ (MIN|MAX)
    |   UINTMAX_MAX

Macros for literals
    The names match the regexp:
        U? INT (8|16|32|64) _C
    Each of these 8 macros takes an integer literal argument, and
    expands it to whatever gibberish the platform needs to make a
    valid literal of at least the specified width.

    Also INTMAX_C(lit) and UINTMAX_C(lit), to do likewise for the
    fattest type (intmax_t or uintmax_t) supported by the platform.

Macros for format specifiers
    There are many dozens of these!  They address the problem that it's
    great you can now ask for, e.g., an int_fast32_t, but you still have
    no idea how big it is so also no idea what to stick in printf or
    scanf formats to do correct I/O on values of that type.

Other limits
    ptrdiff_t:  PTRDIFF_MIN  PTRDIFF_MAX
    sig_atomic_t:  SIG_ATOMIC_MIN  SIG_ATOMIC_MAX
    size_t:  SIZE_MAX
    wchar_t: WCHAR_MIN  WCHAR_MAX
    wint_t:  WINT_MIN   WINT_MAX

I don't expect Python needs more than half a dozen of these, but haven't
given it sufficient thought.  If somebody else beats me to it, I would be
pleased <wink>.

the-very-need-for-names-like-intmax_max-is-a-strong-argument-
    for-euthanasia-ly y'rs  - tim