> -----Original Message----- > From: linux-rdma-owner@xxxxxxxxxxxxxxx [mailto:linux-rdma- > owner@xxxxxxxxxxxxxxx] On Behalf Of Jason Gunthorpe > Sent: Friday, February 09, 2018 10:11 AM > To: Bart Van Assche <Bart.VanAssche@xxxxxxx> > Cc: linux-rdma@xxxxxxxxxxxxxxx > Subject: Re: [PATCH rdma-core] mlx4: Fix 1<<31 expressions > > On Fri, Feb 09, 2018 at 04:01:51PM +0000, Bart Van Assche wrote: > > On Thu, 2018-02-08 at 16:38 -0700, Jason Gunthorpe wrote: > > > enum { > > > - MLX4_WQE_BIND_TYPE_2 = (1<<31), > > > + MLX4_WQE_BIND_TYPE_2 = (1UL<<31), > > > MLX4_WQE_BIND_ZERO_BASED = (1<<30), > > > }; > > > > Hello Jason, > > > > A quote from the C11 standard: > > > > "The expression that defines the value of an enumeration constant > > shall be an integer constant expression that has a value representable > > as an int. [ ... ] Each enumerated type shall be compatible with char, > > a signed integer type, or an unsigned integer type. The choice of type > > is implementation-defined but shall be capable of representing the > > values of all the members of the enumeration." > > > > Does that mean that this change relies on extensions to the C standard? > > Yes, this relies on a common compiler extension to promote the type of enum > constants beyond int. AFAIK all compilers have done this forever, kinda bonkers > it isn't in C11, IMHO. > > As I understand it, the current code is also non-conforming as (1<<31) is > apparently undefined behavior, and at least gcc throws a warning for it in - > Wpedantic mode. > > I did a patch that will make our public headers mostly strictly conforming to C11 > with -Wpedantic set, which I've been wondering if it is worth sending.. > Any reason to use open code instead of using BIT() macro from include/linux/bitops.h which does the same thing? -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
