ENUMSIZE

Pragma equivalent

Purpose

Specifies the amount of storage occupied by enumerations

Syntax


            .-SMALL---.      
>>-ENUM--(--+-INT-----+--)-------------------------------------><
            +-INTLONG-+      
            +-1-------+      
            +-2-------+      
            +-4-------+      
            '-8-------'

Defaults

ENUM(SMALL)

Parameters

SMALL: Specifies that enumerations occupy a minimum amount of storage, which is either 1, 2, 4, or 8 bytes of storage, depending on the range of the enum constants.
INT: Specifies that enumerations occupy 4 bytes of storage and are represented by int.
INTLONG: Valid only when LP64 is specified and for C++ only. It specifies that enumerations occupy 8 bytes of storage and are represented by long if the range of the enum constants exceed the limit for int. Otherwise, the enumerations occupy 4 bytes of storage and are represented by int.
1: Specifies that enumerations occupy 1 byte of storage.
2: Specifies that enumerations occupy 2 bytes of storage
4: Specifies that enumerations occupy 4 bytes of storage.
8: Specifies that enumerations occupy 8 bytes of storage. This suboption is only valid with LP64.

Usage

When the ENUMSIZE option is in effect, you can select the type used to represent all enum constants defined in a compilation unit.

The following tables illustrate the preferred sign and type for each range of enum constants:

Table 1. ENUM constants for C and C++
ENUM Constants	small	1	2	4	8 *	int	intlong * (C++ only)
0..127	unsigned char	signed char	short	int	long	int	int
-128..127	signed char	signed char	short	int	long	int	int
0..255	unsigned char	unsigned char	short	int	long	int	int
0..32767	unsigned short	ERROR	short	int	long	int	int
-32768..32767	short	ERROR	short	int	long	int	int
0..65535	unsigned short	ERROR	unsigned short	int	long	int	int
0..2147483647	unsigned int	ERROR	ERROR	int	long	int	int
-2³¹..2³¹-1	int	ERROR	ERROR	int	long	int	int
0..4294967295	unsigned int	ERROR	ERROR	unsigned int	long	unsigned int (C++ only) ERROR for C	unsigned int
0..(2⁶³-1) *	unsigned long	ERROR	ERROR	ERROR	long	ERROR	long
-2⁶³..(2⁶³-1) *	long	ERROR	ERROR	ERROR	long	ERROR	long
0..2⁶⁴ *	unsigned long	ERROR	ERROR	ERROR	unsigned long	ERROR	unsigned long

Note: The rows and columns marked with asterisks (*) in this table are only valid when the LP64 option is in effect.

Predefined macros

The __ENUM_OPT macro is defined only by the C compiler, which predefines it to 1 when the ENUMSIZE option is in effect; otherwise it is undefined.

Examples

If the specified storage size is smaller than that required by the range of enum constants, an error is issued by the compiler; for example:

     #include <limits.h>
     #pragma enum(1)
     enum e_tag {
         a = 0,
          b = SHRT_MAX /* error */   
      } e_var;
      #pragma enum(reset)