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Re: Possible Issue in ieeefp.h




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


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