[dpdk-dev] "virtual" C++ keyword used in rte_devargs.h and causes compilation error in C++

[Neil Horman]

On Sun, Feb 08, 2015 at 04:31:39AM -0300, Ariel Rodriguez wrote:
> "virtual" is a reserved word in c++. When the c++ compiler "g++" use that
> header in a "extern way (just generate standard typo for function
> identifiers)", there`s not way that the compiler posible "turn off" the
> "virtual" reserved  word. If, for example, you guys use the "new" word ...
> its just the same as virtual.
> 
Hmm, you're right, it seems the C++ specification only uses the extern
"Language" construct to define linkage behavior, it in no way defines keyword
recognition or behavior.

Truthfully, while this would be easy to fix by just changing the name, it might
be a good oportunity to make the rte_devargs struct private.  It really doesn't
need to be public at all, if you had an accessor/iterator function for the list,
and that would implicitly solve the problem by moving all the identifiers out of
any publically accessible namespace

Neil

> Regards.
> 
> On Sun, Feb 8, 2015 at 3:33 AM, Ming Zhao <mzhao at luminatewireless.com>
> wrote:
> 
> > In fact the current rte_devargs.h header is enclosed inside  extern C {}
> > block already. But it looks like it's not sufficient. Also there is also
> > the case that rte_devargs.virtual field could be accessed inside a cpp
> > file.
> >
> > On 02/07/2015 12:23 PM, Neil Horman wrote:
> > > On Fri, Feb 06, 2015 at 11:24:15PM -0800, Ming Zhao wrote:
> > >> The code is in rte_devargs.h:
> > >>
> > >> rte_devargs.h:
> > >>
> > >>                 /** Used if type is RTE_DEVTYPE_VIRTUAL. */
> > >>                 struct {
> > >>                         /** Driver name. */
> > >>                         char drv_name[32];
> > >>                 } virtual;
> > >>         };
> > >>
> > >> Which caused clang compiler to report error when this file is included
> > >> by a cpp file, the error message is:
> > >>
> > >> In file included from net/dpdk/testing/base-test.cc:3:
> > >> In file included from net/dpdk/testing/base-test.h:8:
> > >> third-party/dpdk/lib/librte_eal/common/include/rte_devargs.h:89:5:
> > >> error: 'virtual' can only appear on non-static
> > >>       member functions
> > >>                 } virtual;
> > >>                   ^
> > >>
> > >> I think we should try to pick another name for this field. I would
> > >> suggest calling it "vdev" instead, or I'll be happy to take another name
> > >> if someone comes with a different idea.
> > >>
> > >> Thanks!
> > >> Ming
> > >>
> > > You could do that, but it seems like it shouldn't be necessecary.
> > Shouldn't the
> > > solution just be to encapsulate either the header file or the #include
> > directive
> > > from the C++ file with extern C { }?
> > > Neil
> > >
> >