24/03/2021 17:45, Tyler Retzlaff: > On Wed, Mar 24, 2021 at 09:30:58AM +0100, Thomas Monjalon wrote: > > 24/03/2021 05:26, Tyler Retzlaff: > > > +#ifndef __cplusplus > > > #ifndef asm > > > #define asm __asm__ > > > #endif > > > +#endif > > > > It requires more explanations. > > Which compilers do not define asm? > > What happens with C++ if asm is undefined? > > i guess the subject line on my commit didn't communicate this properly > sorry. > > asm is a keyword in both the C and C++ standards. for C++ the keyword is > not permitted to be re-defined. > > here is the relevant text from the standard, in particular item (2). > > 17.6.4.3.1 Macro names [macro.names] > > 1 > A translation unit that includes a standard library header shall not > #define or #undef names declared in any standard library header. > > 2 > A translation unit shall not #define or #undef names lexically identical > to keywords, to the identifiers listed in Table 3, or to the > attribute-tokens > described in 7.6. > > so when including rte_common.h into a translation unit that is being > compiled C++ the rte_common.h violates the standard by leaking the > #define asm macro. > > this problem appears as soon as you try to build a C++ based dpdk > application with clang using windows C++ runtime and #include <list>.
I understood this part. My question is more about the reason for having this define. I think it is there because some compilers don't have asm keyword, but have __asm__. And maybe that's the case for some C++ compilers. If I'm right, this patch is breaking compilation with some C++ compilers.
