Re: __attribute__ error ("message")

[Jonathan Wakely <jwakely.gcc@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 1477 bytes --]

On Sat, 1 Apr 2023, 17:58 Jonny Grant, <jg@jguk.org> wrote:

>
>
> On 31/03/2023 23:13, Xi Ruoyao wrote:
> > On Fri, 2023-03-31 at 23:12 +0100, Jonny Grant wrote:
> >>
> >>
> >> On 31/03/2023 22:58, Xi Ruoyao wrote:
> >>> On Fri, 2023-03-31 at 22:54 +0100, Jonny Grant wrote:
> >>>> If the error or warning attribute is used on a function
> >>>> declaration
> >>>> and a call to such a function is not eliminated through dead code
> >>>> elimination or other optimizations, an error or warning
> >>>> (respectively)
> >>>> that includes message is diagnosed.
> >>>
> >>> In this example the "call to such a function" is clearly "eliminated
> >>> through" inlining (one of "other optimizations").
> >>>
> >>>> https://godbolt.org/z/n849GPTjj
> >>>
> >>
> >> ok yes, now I understand. The compile_abort() got inlined as abort().
> >>
> >> compile_abort():
> >>         pushq   %rax
> >>         call    abort
> >> main:
> >>         pushq   %rax
> >>         call    abort
> >>
> >>
> >> So if I implement it, I must avoid it being optimized (using pragma
> >> etc as below)
> >
> > Or just __attribute__((noipa)).
>
> That's much clearer.
>
> It does feel a shame the optimizer inlines the function, discarding the
> error("message"), before the attribute error("message") can be triggered.
> But we can just put that __attribute__((noipa)) at least.
>

Why provide a definition? Why do you want to define a function that can
never be called, because calling it gives an error?