Help with bit-field semantics in C and C++

[Gabriel Dos Reis]

Richard Henderson <rth@redhat.com> writes:

[...]

| I wonder if a better representation would be subrange types,
| as seen in Ada.  This case has characteristics:
| 
| 	TREE_CODE (enum_type) == INTEGER_TYPE
| 	TREE_TYPE (enum_type) == compatible_int_type
| 	TYPE_MODE (enum_type) == TYPE_MODE (compatible_int_type)
| 	TYPE_PRECISION (enum_type) == TYPE_PRECISION (compatible_int_type)
| 	TYPE_MIN_VALUE (enum_type) == subrange start value
| 	TYPE_MAX_VALUE (enum_type) == subrange end value
| 
| The precision and mode are set such that we see that mask
| operations are not required, but min and max are set to a
| reduced range so that we can see that we're dealing with a
| constrained set of values.

That is a much improved representation.  The question still remains as
what we do when we switch on enum values.  Am I correctly
understanding you that TYPE_MIN_VALUE and TYPE_MAX_VALUE would be used
as guards when generating jump tables?  Those should not be needed
because enums have values in range.

-- Gaby