[dpdk-dev] [PATCH v6 1/6] lib/eal: implement the family of rte bit operation APIs

[Stephen Hemminger]

On Mon, 23 Dec 2019 05:04:12 +0000
Honnappa Nagarahalli <Honnappa.Nagarahalli at arm.com> wrote:

> <snip>
> 
> > 
> > On Sat, 21 Dec 2019 16:07:23 +0000
> > Honnappa Nagarahalli <Honnappa.Nagarahalli at arm.com> wrote:
> >   
> > > Converting these into macros will help remove the size based duplication of  
> > APIs. I came up with the following macro:  
> > >
> > > #define RTE_GET_BIT(nr, var, ret, memorder) \ ({ \
> > >     if (sizeof(var) == sizeof(uint32_t)) { \
> > >         uint32_t mask1 = 1U << (nr)%32; \
> > >         ret = __atomic_load_n(&var, (memorder)) & mask1;\
> > >     } \
> > >     else {\
> > >         uint64_t mask2 = 1UL << (nr)%64;\
> > >         ret = __atomic_load_n(&var, (memorder)) & mask2;\
> > >     } \
> > > })  
> > 
> > Macros are more error prone. Especially because this is in exposed header file  
> That's another question I have. Why do we need to have these APIs in a public header file? These will add to the ABI burden as well. These APIs should be in a common-but-not-public header file. I am also not sure how helpful these APIs are for applications as these APIs seem to have considered requirements only from the PMDs.

Why do we have to wrap every C atomic builtin? What value is there in that?