Berkeley CSUA MOTD:Entry 22133
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2025/05/24 [General] UID:1000 Activity:popular
5/24    

2001/8/15-16 [Computer/SW/Languages/C_Cplusplus, Computer/SW/Compilers] UID:22133 Activity:moderate
8/15    Is there a way in C to specify that I want a particular enum type
        to be one byte or something small instead of the size of an int?
                typedef enum {ME_FOO, ME_BAR} my_enum_t;
                my_enum_t myVar;
                myVar = ME_FOO;
        I saw that gcc has an option "-fshort-enums", but I'm looking for a
        compiler-independent way, preferably in the source code itself.
        Another possible way is to do this instead
                unsigned char myVar;    /* It's really my_enum_t. */
                myVar = (unsigned char) ME_FOO;
        But that's ugly, plus "sizeof(my_enum_t)" is still the size of an int.
        Thanks in advance.  -- yuen
        \_ if you read your K&R you see that this is left implementation
           dependent.  You have to use a compile pragma, or just use the
           constants and not the enum type.  BTW I saw witort today. -- pld
           \_ Hi Paul!  I never noticed pld was you until you mentioned witort!
              -- yuen
        \_ There's no portable way to do this in ANSI C (C++ doesn't force
           a particular size either -- just a minimum size, AFAIK).
           The following hack might be your best option:
               enum my_enum_t_literals { ME_FOO, ME_BAR };
               typedef unsigned char my_enum_t;
               my_enum_t x; x = ME_FOO; /* Works, no warnings */
           sizeof (my_enum_t) is 1 in this case.  And the intent is
           clear from the naming convention.  -- misha.
           \_ i don't see anywhere in the standard that an enum CAN
              be converted to char. only int and larger (including float).
              i believe that implies that the compiler is free to
              issue a warning. but it would have to be a pretty
              stupid compiler.
              \_  Enum constants are the same as int constants (K&R2 A8.4),
                  and you can assign int to char in C.  Compilers might
                  give warnings if the value doesn't fit, which shouldn't
                  happen here.  C is liberal about primitive conversions,
                  which has some upsides (see Kahan's page about Java) -- misha.
2025/05/24 [General] UID:1000 Activity:popular
5/24    

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