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Member "gnuastro-0.9/bootstrapped/m4/exponentf.m4" (17 Apr 2019, 2862 Bytes) of package /linux/privat/gnuastro-0.9.tar.lz:


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    1 # exponentf.m4 serial 2
    2 dnl Copyright (C) 2007-2008, 2010-2019 Free Software Foundation, Inc.
    3 dnl This file is free software; the Free Software Foundation
    4 dnl gives unlimited permission to copy and/or distribute it,
    5 dnl with or without modifications, as long as this notice is preserved.
    6 AC_DEFUN([gl_FLOAT_EXPONENT_LOCATION],
    7 [
    8   AC_CACHE_CHECK([where to find the exponent in a 'float'],
    9     [gl_cv_cc_float_expbit0],
   10     [
   11       AC_RUN_IFELSE(
   12         [AC_LANG_SOURCE([[
   13 #include <float.h>
   14 #include <stddef.h>
   15 #include <stdio.h>
   16 #include <string.h>
   17 #define NWORDS \
   18   ((sizeof (float) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
   19 typedef union { float value; unsigned int word[NWORDS]; } memory_float;
   20 static unsigned int ored_words[NWORDS];
   21 static unsigned int anded_words[NWORDS];
   22 static void add_to_ored_words (float x)
   23 {
   24   memory_float m;
   25   size_t i;
   26   /* Clear it first, in case
   27      sizeof (float) < sizeof (memory_float).  */
   28   memset (&m, 0, sizeof (memory_float));
   29   m.value = x;
   30   for (i = 0; i < NWORDS; i++)
   31     {
   32       ored_words[i] |= m.word[i];
   33       anded_words[i] &= m.word[i];
   34     }
   35 }
   36 int main ()
   37 {
   38   size_t j;
   39   FILE *fp = fopen ("conftest.out", "w");
   40   if (fp == NULL)
   41     return 1;
   42   for (j = 0; j < NWORDS; j++)
   43     anded_words[j] = ~ (unsigned int) 0;
   44   add_to_ored_words (0.25f);
   45   add_to_ored_words (0.5f);
   46   add_to_ored_words (1.0f);
   47   add_to_ored_words (2.0f);
   48   add_to_ored_words (4.0f);
   49   /* Remove bits that are common (e.g. if representation of the first mantissa
   50      bit is explicit).  */
   51   for (j = 0; j < NWORDS; j++)
   52     ored_words[j] &= ~anded_words[j];
   53   /* Now find the nonzero word.  */
   54   for (j = 0; j < NWORDS; j++)
   55     if (ored_words[j] != 0)
   56       break;
   57   if (j < NWORDS)
   58     {
   59       size_t i;
   60       for (i = j + 1; i < NWORDS; i++)
   61         if (ored_words[i] != 0)
   62           {
   63             fprintf (fp, "unknown");
   64             return (fclose (fp) != 0);
   65           }
   66       for (i = 0; ; i++)
   67         if ((ored_words[j] >> i) & 1)
   68           {
   69             fprintf (fp, "word %d bit %d", (int) j, (int) i);
   70             return (fclose (fp) != 0);
   71           }
   72     }
   73   fprintf (fp, "unknown");
   74   return (fclose (fp) != 0);
   75 }
   76         ]])],
   77         [gl_cv_cc_float_expbit0=`cat conftest.out`],
   78         [gl_cv_cc_float_expbit0="unknown"],
   79         [gl_cv_cc_float_expbit0="word 0 bit 23"])
   80       rm -f conftest.out
   81     ])
   82   case "$gl_cv_cc_float_expbit0" in
   83     word*bit*)
   84       word=`echo "$gl_cv_cc_float_expbit0" | sed -e 's/word //' -e 's/ bit.*//'`
   85       bit=`echo "$gl_cv_cc_float_expbit0" | sed -e 's/word.*bit //'`
   86       AC_DEFINE_UNQUOTED([FLT_EXPBIT0_WORD], [$word],
   87         [Define as the word index where to find the exponent of 'float'.])
   88       AC_DEFINE_UNQUOTED([FLT_EXPBIT0_BIT], [$bit],
   89         [Define as the bit index in the word where to find bit 0 of the exponent of 'float'.])
   90       ;;
   91   esac
   92 ])