Calling all C language lawyers for help: I am wondering whether empty structures are allowed or not. assuming either c99 or c11, whichever more favourable. To quote the standard,
6.2.6.1 Except for bit-fields, objects are composed of contiguous sequences of one or more bytes, the number, order, and encoding of which are either explicitly specified or implementation-defined.
This could imply that an empty struct has a non-zero size (so a C++ like behaviour), however, 6.2.5-20 says: "A structure type describes a sequentially allocated nonempty set of member objects". So I thought that I can circumvent it the following way: struct { int dummy: 0; } variable;
One would have to remove the declarator, yielding struct { int : 0; } variable;, per 6.7.2.1.4: "The expression that specifies the width of a bit-field shall be an integer constant expression with a nonnegative value that does not exceed the width of an object of the type that would be specified were the colon and expression omitted.) If the value is zero, the declaration shall have no declarator."
So finally, whether we can have empty structs or not depends on whether int : 0 counts as a member object, but i can't find anything that would be conclusive on this matter. I have already observed that the C standard treats zero size bit-fields specially, but the only relevant bit of information I could find was 6.7.2.1.12: "As a special case, a bit-field structure member with a width of 0 indicates that no further bit-field is to be packed into the unit in which the previous bit-field, if any, was placed."
Any ideas?
N.B. the wording in 6.7.2.1.4 says "non-negative", not "positive", meaning that the width of 0 is technically allowed as a "normal" width.
