On Thu, 27 Apr 2023 at 16:58, Marek Polacek wrote:
> On Thu, Apr 27, 2023 at 12:16:34PM +0100, Jonathan Wakely via Gcc-patches
> wrote:
> > C2x adds the ability to give an enumeration type a fixed underlying
> > type, as C++ already has. The -fshort-enums option alters the compiler's
> > choice of underlying type, but when it's fixed the compiler can't
> > choose.
> >
> > Similarly for C++ -fstrict-enums has no effect with a fixed underlying
> > type, because every value of the underlying type is a valid value of the
> > enumeration type.
> >
> > This caused confusion recently: https://gcc.gnu.org/PR109532
> >
> > OK for trunk?
>
> LGTM.
>
That's an ack C front end reviewer (thanks!), do I need an ack from a
C++/docs/global review too, or can I push?
>
> > -- >8 --
> >
> > gcc/ChangeLog:
> >
> > * doc/invoke.texi (Code Gen Options): Note that -fshort-enums
> > is ignored for a fixed underlying type.
> > (C++ Dialect Options): Likewise for -fstrict-enums.
> > ---
> > gcc/doc/invoke.texi | 4 ++++
> > 1 file changed, 4 insertions(+)
> >
> > diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> > index 2f40c58b21c..0f91464f8c0 100644
> > --- a/gcc/doc/invoke.texi
> > +++ b/gcc/doc/invoke.texi
> > @@ -3495,6 +3495,8 @@ defined in the C++ standard; basically, a value
> that can be
> > represented in the minimum number of bits needed to represent all the
> > enumerators). This assumption may not be valid if the program uses a
> > cast to convert an arbitrary integer value to the enumerated type.
> > +This option has no effect for an enumeration type with a fixed
> underlying
> > +type.
> >
> > @opindex fstrong-eval-order
> > @item -fstrong-eval-order
> > @@ -18303,6 +18305,8 @@ Use it to conform to a non-default application
> binary interface.
> > Allocate to an @code{enum} type only as many bytes as it needs for the
> > declared range of possible values. Specifically, the @code{enum} type
> > is equivalent to the smallest integer type that has enough room.
> > +This option has no effect for an enumeration type with a fixed
> underlying
> > +type.
> >
> > @strong{Warning:} the @option{-fshort-enums} switch causes GCC to
> generate
> > code that is not binary compatible with code generated without that
> switch.
> > --
> > 2.40.0
> >
>
> Marek
>
>
