Re: [avr-llvm-devel] Interrupt handling

[Borja F. <bor...@gm...>]

In my opinion the best thing should be to error out, it doesn't make sense
to set this attributes in non void functions. Technically from a codegen
perspective it doesn't matter because registers are all saved and restored
unless the naked attrib is set so it wouldnt't make a difference except for
some useless instructions. Doing this kind of things shows that the
programmer doesn't understand what he's doing.
I issued the warning to be sort of backwards compat with gcc, although in
this case we would be supporting wrong code. In conclusion, error out.

2012/3/6 Weddington, Eric <Eri...@at...>

>
> Well, we don't have to slavishly follow GCC either.
>
> What do you think?
>
> If you were a programmer, would you want the compiler to warn you, then
> not apply the attribute and continue compilation?
>
> Should the compiler assume that you did not want the attribute to be
> applied in the case of a non-void function or one with arguments?
>
> The compiler really doesn't know what the fix should be. I would think,
> that in this case, it really is equivalent to a syntax error. These
> attributes are only allowed on a non-void, non-argument function.
> Otherwise, the user needs to the fix the code to expressly say what
> needs to be done.
>
> This is outside the realm of the C standard, since we're dealing with
> function attributes and ISRs. Again, what do you think?
>
> Eric Weddington
>
> > -----Original Message-----
> > From: Borja Ferrer [mailto:bor...@gm...]
> > Sent: Tuesday, March 06, 2012 12:22 PM
> > To: Weddington, Eric
> > Cc: avr...@li...
> > Subject: Re: [avr-llvm-devel] Interrupt handling
> >
> > It issues a warning, so, it doesn't apply the attribute and it doesn't
> abort
> > compilation. I checked gcc and it warns aswell. However i can error
> out if
> > it's better, i leave that up to you.
> >
> >
> > 2012/3/6 Weddington, Eric <Eri...@at...>
> >
> >
> >
> >
> >       > -----Original Message-----
> >       > From: Borja Ferrer [mailto:bor...@gm...]
> >
> >       > Sent: Tuesday, March 06, 2012 11:57 AM
> >       > To: Weddington, Eric
> >       > Cc: avr...@li...
> >       > Subject: Re: [avr-llvm-devel] Interrupt handling
> >       >
> >
> >       > I've added some checks to the frontend when setting the
> >       signal/interrupt
> >       > attribute that are the following:
> >       >
> >       > 1) warn when the attrib is used in things that aren't function
> >       declarations.
> >       > 2) warn when the function has arguments
> >       > 3) warn when the function doesnt return a void
> >       >
> >       > If anybody can think of any more checks that are required let
> me know.
> >       >
> >       > Oh, and here are the warning messages printed for cases 2 and
> 3
> >       respectively,
> >       > again, if somebody has a better descriptive string or with
> better
> >       english I'll
> >       > change it:
> >       >
> >       > 2) "'%0' attribute only applies to functions with no
> arguments"
> >       > 3) "'%0' attribute only applies to functions with a void
> return type"
> >       > where %0 is either interrupt or signal
> >       >
> >
> >
> >       Semantics question: Do you mean that it issues just a *warning*?
> Or does
> >       it error out on these?
> >
> >
>
>