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RE: No effect of -fshort-enums..is it a bug
- From: "Gaurav Gautam, Noida" <gauravga at noida dot hcltech dot com>
- To: "Dave Korn" <dave dot korn at artimi dot com>, "John Love-Jensen" <eljay at adobe dot com>, <gcc at gcc dot gnu dot org>, "MSX to GCC" <gcc-help at gcc dot gnu dot org>
- Date: Fri, 23 Sep 2005 19:34:40 +0530
- Subject: RE: No effect of -fshort-enums..is it a bug
>
> > Hi Gaurav,
> >
> >> Please confirm which of the two outputs is correct and why is there
a
> > difference in the output of two versions of compiler?
> >
> > Both outputs are "correct".
> >
>
>
> No, the standard is entirely unambiguous:
>
> --------------------------------------------------------
> 6.4.4.3 Enumeration constants
> Syntax
> 1 enumeration-constant:
> identifier
> Semantics
> 2 An identifier declared as an enumeration constant has type int.
> --------------------------------------------------------
>
> The enumeration constants denoted by the identifiers a, b, and c are
> therefore of type int and must have size 4 (on a standard 32-bit
system),
> regardless of the size of the enumerated type aa.
Thank you all for your replies. But I have another question to ask
Consider another example
#include <stdio.h>
int main()
{
enum ff {
p = 0, q = 4294967295, r
};
printf("size = %d %d %d\n", sizeof(enum ff),sizeof(q),
sizeof(r));
printf("value= %d %d %d\n", p,q,r);
}
Its output is with default options on gcc :
size = 8 8 8
value= 0 -1 0
Enumerator are supposed to be int and must have size 4. why are they
being treated as long here and taking 8 bytes? Size of int on my machine
is 4.
Also the compiler doesn't even gives a warning when the tc is compiled.
>
>
> > (Neither output is compliant to the standard, of course, as -fshort-
> enums
> > is a deviation from the standard.)
>
> Nope, the standard is entirely unambiguous:
>
> --------------------------------------------------------
> 6.7.2.2 Enumeration specifiers
>
> 4 Each enumerated type shall be compatible with an integer type. The
> choice
> of type is
> implementation-defined,97) but shall be capable of representing the
values
> of all the
> members of the enumeration. The enumerated type is incomplete until
after
> the } that
> terminates the list of enumerator declarations.
> --------------------------------------------------------
>
> The choice of what integer type to use to store a value of an
enumerated
> type is implementation-defined, and if a char is big enough to
represent
> all
> the values, the implementation is at liberty to use a char.
>
>
>
> cheers,
> DaveK
> --
> Can't think of a witty .sigline today....