Re: [PATCH] newlib: switch to autoconf long double wider macro

Mike Frysinger <[email protected]> Fri, 21 Jan 2022 07:39:11 -0500

Newsgroups	gmane.comp.lib.newlib
Message-ID	<Yeqpb+RqYl1lvBqq@vapier>

On 21 Jan 2022 12:27, Corinna Vinschen wrote:
> On Jan 21 00:04, Mike Frysinger wrote:
> > Now that we require a recent version of autoconf, we can rely on this
> > macro existing.  It has inverted semantics from the existing test (it
> > looks for "is wider" instead of "is equal"), so we have to invert the
> > check when creating our _LDBL_EQ_DBL.
> > ---
> >  newlib/configure    | 72 +++++++++++++++++++++++++++++----------------
> >  newlib/configure.ac | 22 ++------------
> >  newlib/newlib.hin   |  4 +++
> >  3 files changed, 53 insertions(+), 45 deletions(-)
> 
> Looks right to me, please push.

for posterity, i'll note that autoconf uses a different (more comprehensive)
testing method that ultimately arrives at a diff answer than what newlib is
atm.  for aarch64, _LDBL_EQ_DBL is now defined when it wasn't before.

newlib today is doing:
#if DBL_MANT_DIG == LDBL_MANT_DIG && \
    LDBL_MIN_EXP == DBL_MIN_EXP   && \
    LDBL_MAX_EXP == DBL_MAX_EXP
  #define _LDBL_EQ_DBL
 #else
  #error "LDBL != DBL"
#endif

while autoconf is doing:
       (0 < ((DBL_MAX_EXP < LDBL_MAX_EXP)
          + (DBL_MANT_DIG < LDBL_MANT_DIG)
          - (LDBL_MAX_EXP < DBL_MAX_EXP)
          - (LDBL_MANT_DIG < DBL_MANT_DIG)))
       && (int) LDBL_EPSILON == 0
-mike

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