Re: [Qemu-devel] [PATCH 11/67] target/arm: Add stubs for aa32 decodetree

[Aleksandar Markovic]

On Fri, Aug 9, 2019 at 4:55 PM Richard Henderson <
address@hidden> wrote:

> On 8/9/19 3:31 AM, Aleksandar Markovic wrote:
> >
> >
> > On Thu, Aug 8, 2019 at 5:43 PM Richard Henderson <
> address@hidden
> > <mailto:address@hidden>> wrote:
> >
> >     On 8/8/19 4:41 AM, Aleksandar Markovic wrote:
> >     >     +/*
> >     >     + * Include the generated decoders.
> >     >     + * Note that the T32 decoder reuses some of the trans_*
> functions
> >     >     + * initially declared by the A32 decoder, which results in
> duplicate
> >     >     + * declaration warnings.  Suppress them.
> >     >     + */
> >     >     +
> >     >     +#ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE
> >     >     +# pragma GCC diagnostic push
> >     >     +# pragma GCC diagnostic ignored "-Wredundant-decls"
> >     >     +# ifdef __clang__
> >     >     +#  pragma GCC diagnostic ignored "-Wtypedef-redefinition"
> >     >     +# endif
> >     >     +#endif
> >     >     +
> >     >
> >     >
> >     > This looks more like a "band aid" solution rather than the right
> one.
> >
> >     What would the "right" solution be, would you say?
> >
> >
> > The right (without quotation marks) solution is not to generate the code
> that
> > generates compiler complaints.
>
> That would be impossible with the information supplied.
>

That limitation is a fault of decodetree design, not an obstacle per se.


> Emitting zero declarations will result in invalid C.  We ensure that each
> individual decodetree file does not emit duplicates.  However, there is no
> knowledge across separate decodetree files about which declarations are
> duplicate.
>
> In this particular case, I do not even agree that the warnings themselves
> are
> useful.  I suppose it's not impossible that they could diagnose some
> weirdness
> in a code base, where a function is declared in multiple headers or a patch
> application has gone awry leaving multiple sequential declarations, but
> honestly how often does that happen?
>
> I suppose with some work, we could not invoke decodetree multiple times,
> but
> give it all of the input files at once, producing a single output file.
>
>
> > Obviously, in this case, decodetree-generated code shows that it is
> > inferior to human-generated code.
>
> That is not obvious at all.  Moreover, I disagree strongly.
>
>
OK. I'm fine with your disagreeing. That why open source exists - to have
opportunities to hear different views.

Yours,
Aleksandar


> r~
>