Re: newlib ieeefp.h again

[Craig Howland <howland at LGSInnovations dot com>]

On 03/23/2017 02:58 AM, Sebastian Huber wrote:
> On 23/03/17 00:17, Andrew Johnson wrote:
> > Hi Joel & Craig,
> >
> > Hopefully you remember this email conversation from November:
> >
> > https://sourceware.org/ml/newlib/2016/msg01117.html
> >
> > I just built the RTEMS master branch for the uC5282 BSP, and found the
> > same problem with the ieeefp.h header when building EPICS Base using the
> > result. I think I can explain what's happening.
> >
> > Newlib's setting for _LDBL_EQ_DBL (in newlib.h) needs to change based on
> > the particular CPU being compiled for. Here's some evidence:
>
> Yes, this definition of _LDBL_EQ_DBL is wrong, since it depends on the 
> multilib. For example we have in the GCC build tree:
>
> grep _LDBL_EQ_DBL `find -name newlib.h`
> ./m68k-rtems4.12/m68040/softfp/newlib/newlib.h:/* #undef _LDBL_EQ_DBL */
> ...
>
> In the installation tree:
>
> grep _LDBL_EQ_DBL `find -name newlib.h`
> ./m68k-rtems4.12/include/newlib.h:/* #undef _LDBL_EQ_DBL */
>
> So, only one random newlib.h is copied to the installation tree, therefore all 
> newlib.h of the build tree must be identical.
>
> I would move the _LDBL_EQ_DBL definition to <ieeefp.h> based on compiler 
> provided defines.
The primary question is whether this is truly possible or not, which will depend 
upon both what compiler and how old of a compiler version newlib wants to 
support.  Back in 2009 when _LDBL_EQ_DBL was added to newlib.hin, this was not 
really possible as both float.h and compiler predefines were spotty.  As long as 
we don't need to go back too many versions, it ought to be fine to do it at 
build time now.
Craig