Possible Issue in ieeefp.h

[Craig Howland]

On 11/21/2016 11:38 AM, Joel Sherrill wrote:
>
>
> On 11/21/2016 10:26 AM, Craig Howland wrote:
>> On 11/21/2016 11:08 AM, Joel Sherrill wrote:
>>> Hi
>>>
>>> An RTEMS user has tried to build GNU FORTRAN. It used to build
>>> and test OK. I am copying his report and my suggestion. I think
>>> the constants tested in ieeefp.h do NOT match those predefined
>>> by GCC. I need someone more knowledgable to confirm.
>>>
>>> Thanks.
>>>
>>> --joel
>>>
>>>>
>>>>
>>>> On Mon, Nov 21, 2016 at 9:24 AM, Ricardo Derbes <rmderbes@gmail.com> wrote:
>>>> Hello.
>>>> I'm trying to build rtems toolchain for i386 using
>>>> rtems-source-builder with fortran support (--with-fortran option).
>>>> The RSB I'm using has been dowloaded from git, commit
>>>> 534332f22a66f16b4022e87ae50c11ff20c98dcb from Sep 12 2016.
>>>>
>>>> ...
>>>>
>>>> As for my application I need fortran support, how can I fix this problem?
>>>> As long I can see, all symbols that the compiler claims as undeclared
>>>> are indeed declared and accessible in file
>>>> ~/devel4.12-i386.fortran/rtems-source-builder/rtems/build/i386-rtems4.12-gcc-6-20160609-newlib-2.4.0.20160527-x86_64-linux-gnu-1/gcc-6-20160609/newlib/libc/include/ieeefp.h 
>>>>
>>>>
>>>> May be it's missing a symbol, e.g a proper value for LDBL_MANT_DIG ?
>>>>
>>>>
>>>> I see that GCC predefines these symbols:
>>>>
>>>> #define __FLT_MANT_DIG__ 24
>>>> #define __DEC64_MANT_DIG__ 16
>>>> #define __LDBL_MANT_DIG__ 53
>>>> #define __DBL_MANT_DIG__ 53
>>>> #define __DEC32_MANT_DIG__ 7
>>>> #define __DEC128_MANT_DIG__ 34
>>>>
>>>> And ieeefp.h in newlib has this:
>>>>
>>>> #elif LDBL_MANT_DIG == 53
>>>> /* This happens when doubles are 32-bits and long doubles are 64-bits.  */
>>>> #define EXT_EXPBITS     11
>>>> #define EXT_FRACHBITS   20
>>>> #define EXT_FRACLBITS   32
>>>> #define __ieee_ext_field_type unsigned long
>>>>
>>>> I am suspicious that the ifdef should use __LDBL_MANT_DIG__ not LDBL_MANT_DIG.
>>>>
>> ieeefp.h is definitely intending to use LDBL_MANT_DIG.  This is the C-standard
>> defined name which is supposed to be defined in float.h, and which ieeefp.h
>> directly states it is relying on.  Apparently the float.h being used is not
>> properly defined/set up, and this is what needs to be corrected.
>
> I have never poked in this area before. Where is this generated?
> Help on where to look and what could be broken is appreciated.
>
> Thanks.
>
>> Craig
>>
>
> --joel
float.h is generally assumed to be supplied by the compiler, in a fashion 
similar to stdarg.h, as it contains compiler-specific sizes.  (I just took a 
look at the GCC 4.1.1 PowerPC cross compiler's float.h, and they pretty much 
just turn their internal defines into the C-required names.)  Probably the 
--with-fortran option is messing things up.  Could you perhaps build without it 
just to get the right float.h, and then use that as a bootstrap of sorts to make 
the --with-fortran build work?  (Any way of finding the right float.h for your 
GCC version should work.)
Craig