Re: [dpdk-dev] [PATCH] eal: standard c++ forbids defining the keyword asm as a macro

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed, 24 Mar 2021 18:52:40 +0100
Thomas Monjalon <thomas@monjalon.net> wrote:

> 24/03/2021 18:28, Tyler Retzlaff:
> > On Wed, Mar 24, 2021 at 06:04:08PM +0100, Thomas Monjalon wrote:  
> > > 24/03/2021 17:45, Tyler Retzlaff:
> > > 
> > > 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.  
> > 
> > so to qualify. you mean maybe it is breaking compilation of c++ in a
> > compiler that explicitly violates c++ standard when compiling c++? that
> > would mean it is not a c++ compiler.  
> 
> The asm keyword is part of all C++ standards?
> It seems asm is non-standard in C,
> that's why we use __asm__.
> 
> > in general i don't think it is a good practice to have dpdk introduce
> > names into the application namespace unqualified, but the point you make
> > is valid it can break c++ compilation if something was using this macro
> > as a convenience to the compiler specific extension __asm__. there will
> > be further issues with varying syntaxes that __asm__-style extensions
> > take from compiler to compiler as well.  
> 
> Yes we need to make sure there is no specific extension involved.
> Is C++ asm the same as the C __asm__?
> 
> > would you prefer that i change the preprocessor protection to include only
> > windows? since i'm certain that this will break for any c++ compiler on
> > windows the moment any stl header is included.  
> 
> No, C++ is probably the right scope.
> 
> > let me know how to adjust the patch i'll submit a new version.  
> 
> I don't know yet. I would like to understand the global picture,
> and have it properly documented in this commit log.
> 

There should be some test for C++ application use of API.
There doesn't appear to be one in the current CI suite.