Re: [PATCH 1/1] eal: add C++ include guard in generic/rte_vect.h

[Ashish Sadanandan <ashish.sadanandan@gmail.com>]

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On Fri, Feb 2, 2024 at 2:41 AM Bruce Richardson <bruce.richardson@intel.com>
wrote:

> On Fri, Feb 02, 2024 at 10:18:23AM +0100, Thomas Monjalon wrote:
> > 02/02/2024 06:13, Ashish Sadanandan:
> > > The header was missing the extern "C" directive which causes name
> > > mangling of functions by C++ compilers, leading to linker errors
> > > complaining of undefined references to these functions.
> > >
> > > Fixes: 86c743cf9140 ("eal: define generic vector types")
> > > Cc: nelio.laranjeiro@6wind.com
> > > Cc: stable@dpdk.org
> > >
> > > Signed-off-by: Ashish Sadanandan <ashish.sadanandan@gmail.com>
> >
> > Thank you for improving C++ compatibility.
> >
> > I'm not sure what is best to fix it.
> > You are adding extern "C" in a file which is not directly included
> > by the user app. The same was done for rte_rwlock.h.
> > The other way is to make sure this include is in an extern "C" block
> > in lib/eal/*/include/rte_vect.h (instead of being before the block).
> >
> > I would like we use the same approach for all files.
> > Opinions?
> >
> I think just having the extern "C" guard in all files is the safest choice,
> because it's immediately obvious in each and every file that it is correct.
> Taking the other option, to check any indirect include file you need to go
> finding what other files include it and check there that a) they have
> include guards and b) the include for the indirect header is contained
> within it.
>
> Adopting the policy of putting the guard in each and every header is also a
> lot easier to do basic automated sanity checks on. If the file ends in .h,
> we just use grep to quickly verify it's not missing the guards. [Naturally,
> we can do more complete checks than that if we want, but 99% percent of
> misses can be picked up by a grep for the 'extern "C"' bit]
>
> /Bruce
>

100% agree with Bruce. It's a valid ideological argument that private
headers
don't need such safeguards, but it's difficult to enforce and easy to break
during refactoring.

- Ashish

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