Have you thought about adding a special case in sys/config.h which
when it has the appropriate conditions (platform plus compiler flag) will
define/redefine _LDBL_EQ_DBL?

It gets included as part of _ansi.h and after newlib.h.

-- Jeff J.


On Tue, Sep 26, 2023 at 10:43 AM Joel Sherrill <joel@rtems.org> wrote:

> Hi
>
> I wondered when we reorganized LDBL_EQ_DBL logic if there wouldn't be a
> multilib edge case. Chris encountered it.
>
> Attached is a simple test program based on the autoconf probe in
> configure.ac that can be preprocessed with different CPU/ABI flags. The
> following shows that the default on m68k is not the same as for the 5282.
>
> $ m68k-rtems6-gcc -O2 -E ldbl.c | less
>
> $ m68k-rtems6-gcc -O2 -E -mcpu=5282 ldbl.c | less
>
> Turns out the default flags end up with LDBL_EQ_DBL isn't defined but it
> should be for -mcpu=5282 builds.
>
> I don't know any mechanism to add header file variants in newlib by
> multilib, so I we need to consider moving this to a dynamic check.
>
> Any thoughts on where to move this?
>