Hi Jason,
On 24/05/2019 08.07, Jason Gunthorpe wrote:
> On Thu, May 23, 2019 at 11:14:42PM -0700, Gerd Rausch wrote:
>
>> I can't say that I'm thrilled with this behavior though,
>> as it appears error-prone:
>> As soon as an enum value goes out of range for an "int", the
>> type silently changes, potentially rendering structures and functions silently incompatible.
>> It's quite the pitfall (e.g. the foo.c vs bar.c case above).
>
> Indeed, I would be very careful using this extension with
> non-anonymous enums :)
>
> However, an anonymous enum can never have storage allocated, so it
> doesn't experience any ABI concern.
>
Sure it can:
% cat foo.c
struct foo {
enum { FOO = 1UL << 31 } foo;
} foo = { FOO };
% gcc -Wall -g -c foo.c && gdb -batch -ex 'print sizeof foo' foo.o
$1 = 4
% cat bar.c
struct bar {
enum { FOO = 1UL << 31, BAR = -1 } bar;
} bar = { BAR };
% gcc -Wall -g -c bar.c && gdb -batch -ex 'print sizeof bar' bar.o
$1 = 8
> It is a good and very useful extension, it is unfortuntate that C11
> did not standardize it. (C++11 did though)
>
Thanks for the info again.
I guess I'm still stuck in 99 ;-)
Cheers,
Gerd
