Re: [PATCH 3/3] powerpc: enable support for GCC plugins

[Andrew Donnellan]

On 09/12/16 05:06, Kees Cook wrote:
> > i don't think that this is the right approach. there's a general and a special
> > issue here, both of which need different handling.
> >
> > the general problem is to detect problems related to gcc plugin headers and
> > notify the users about solutions. emitting various messages from a Makefile
> > is certainly not a scalable approach, just imagine how it will look when the
> > other 30+ archs begin to add their own special cases... if anything, they
> > should be documented in Documentation/gcc-plugins.txt (or a new doc if it
> > grows too big) and the Makefile message should just point at it.

I think I agree in principle - Makefiles are already unreadable enough 
without a million special cases.

> > as for the solutions, the general advice should enable the use of otherwise
> > failing gcc versions instead of forcing updating to new ones (though the
> > latter is advisable for other reasons but not everyone's in the position to
> > do so easily). in my experience all one needs to do is manually install the
> > missing files from the gcc sources (ideally distros would take care of it).

If someone else is willing to write up that advice, then great.

> > the specific problem addressed here can (and IMHO should) be solved in
> > another way: remove the inclusion of the offending headers in gcc-common.h
> > as neither tm.h nor c-common.h are needed by existing plugins. for background,

We can't build without tm.h: http://pastebin.com/W0azfCr0

And we get warnings without c-common.h: http://pastebin.com/Aw8CAj10

> > as for the location of c-common.h, upstream gcc moved it under c-family in
> > 2010 after the release of 4.5, so it should be where gcc-common.h expects
> > it and i'm not sure how it ended up at its old location for you.
>
> That is rather odd. What distro was the PPC test done on? (Or were
> these manually built gcc versions?)

These were all manually built using a script running on a Debian box. 
Installing precompiled distro versions of rather old gccs would have 
been somewhat challenging. I've just rebuilt 4.6.4 to double check that 
I wasn't just seeing things, but it seems that it definitely is still 
putting c-common.h in the old location.

--
Andrew Donnellan              OzLabs, ADL Canberra
andrew.donnellan@xxxxxxxxxxx  IBM Australia Limited