sizeof (integral types)

[Michael Meissner]

In article <7.UUL1.3#5109 at pantor.UUCP> richard at pantor.UUCP (Richard Sargent) writes:
| gwyn at smoke.BRL.MIL (Doug Gwyn) in Message-ID: <10044 at smoke.BRL.MIL> writes:
| > 
| > In article <12005 at paris.ics.uci.edu> Doug Schmidt <schmidt at glacier.ics.uci.edu> writes:
| > >I realize the relation short <= int <= long holds, I'm just curious
| > >whether there is any minimum that these basic types must meet (e.g.,
| > >short >= 16 bits, etc.).
| > 
| > chars are at least 8 bits,
| > shorts are at least 16 bits,
| > longs are at least 32 bits.
| 
| I quote from the ANSI C DRAFT dated January 11, 1988, Section 3.1.2.5:
| 
|    An object declared as type  char  is large enough to store any member
|    of the basic execution character set.  ...
| 
|    There are four _signed integer types_, designated as  signed char,
|    short int,  int,  and  long int.  ...
| 
|    ...  A "plain"  int  object has the natural size SUGGESTED by the
|    architecture of the execution environment ( ... in the header <limits.h>).
|    In the list of signed integer types above, the range of values of each
|    type is a subrange of the values of the next type in the list.
| 
| Please note that this definition explicitly avoids any claims about the sizes
| of the types except for the "<=" business in the first message.  It most
| definitely does NOT say anything about 8, 16, or 32 bits!  In fact, the
| definition permits implementations of 8 bit longs and others of 32 bit chars!
| (Of course, no one in their right mind would try to sell such a product,
| but it is not forbidden by the language definition.)

And I quote from an eariler section (2.2.4.2) in the draft, dated
December 7, 1988 -- it seems like it's nailed down to me.  By the way,
this section has been in the draft for at least two years.

    The values given below shall be replaced by constant expressions
suitable for use in #if preprocessing directives.  Moreoever, except
for CHAR_BIT and MB_LEN_MAX, the following shall by replaced by
expressions that have the same type as would an expression that is an
object of the corresponding type converted according to the integral
promotions.  Their implemtation-defined values shall be equal or
greater in magnitude (absolute value) to those shown, with the same
sign.

* number of bits for smallest object that is not a bit-field (byte)

CHAR_BIT	8

* minimum value for an object of type signed char

SCHAR_MIN	-127

* maximum value for an object of type signed char

SCHAR_MAX	+127

* maximum value for an object of type unsigned char

UCHAR_MAX	255

* minimum value for an object of type char

CHAR_MIN	see below

* maximum value for an object of type char

CHAR_MAX	see below

* maximum number of bytes in a multibyte character, for any supported
locale.

MB_LEN_MAX	1

* minimum value for an object of type short int

SHRT_MIN	-32767

* maximum value for an object of type short int

SHRT_MAX	32767

* maximum value for an object of type unsigned short int

USHRT_MAX	65535

* minimum value for an object of type int

INT_MIN		-32767

* maximum value for an object of type int

INT_MAX		32767

* minimum value for an object of type long int

LONG_MIN	-2147483647

* maximum value for an object of type long int

LONG_MAX	2147483647

* maximum value for an object of type unsigned long int

ULONG_MAX	4294967295

    If the value of an object of type char is treated as a signed
integer when used in an expression, the value of CHAR_MIN shall be the
same as SCHAR_MIN and the value of CHAR_MAX shall be the same as
SCHAR_MAX.  Otherwise, the value of CHAR_MIN shall be 0 and the value
of CHAR_MAX shall be the same as UCHAR_MAX. [see 3.1.2.5]

--
Michael Meissner, Data General.
Uucp:		...!mcnc!rti!xyzzy!meissner		If compiles were much
Internet:	meissner at dg-rtp.DG.COM			faster, when would we
Old Internet:	meissner%dg-rtp.DG.COM at relay.cs.net	have time for netnews?