On 07/25/10 20:12, Kostik Belousov wrote:
On Mon, Jul 26, 2010 at 01:36:07AM +1000, Bruce Evans wrote:
On Sat, 24 Jul 2010, Stefan Farfeleder wrote:
declaring enums like this is not standard C code (seems to be a GCC
extension). I don't think we should use this feature in our headers.
This is unfortunate. This is because the size of an enum variable
depends on its complete declaration. This is an error unconditionaly
with TenDRA. It takes -pedantic to get a warning from gcc.
I looked at the C99, and indeed, there is an explicit sentence
"A type specifier of the form enum identifier without an enumerator list
shall only appear after the type it specifies is complete."
I fully agree with Bruce that this is unfortunate, or rather, makes
enum tag declaration completely unuseful. gcc extension greatly simplifies
dealing with the headers pollution.
On the other hand, I disagree with the statement that the size of the
enum variable depends on the full declaration. It seems that C99
defines values of the enum to by of type int, and both i386 and
amd64 ABIs define enums as represented by 4-byte integers.
Yes, I am aware that C++ allows the enum to be assigned the
the shortest arithmetic type that can represent all enum values.
This is not actually true. Try adding a value that requires a 64-bit int
to your enum -- it will become 8 bytes. Also, the signedness of the type
depends on the values in the enumeration.
-Nathan
_______________________________________________
svn-src-head@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/svn-src-head
To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
