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annotate m4/exponentf.m4 @ 10638:28050ad34088

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Fix getaddrinfo emulation for systems with struct sockaddr.sa_len. 2008-10-13 Paolo Bonzini <bonzini@gnu.org> fix getaddrinfo emulation for systems with struct sockaddr.sa_len * m4/getaddrinfo.m4 (gl_PREREQ_GETADDRINFO): Detect struct sockaddr.sa_len. * lib/getaddrinfo.c (getaddrinfo): Set it if appropriate.
author Paolo Bonzini <bonzini@gnu.org>
date Mon, 13 Oct 2008 19:49:44 +0200
parents 12944217dba7
children b5e42ef33b49
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12944217dba7 Move macros for finding floating-point exponents into separate M4 files.
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1 # exponentf.m4 serial 1
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2 dnl Copyright (C) 2007-2008 Free Software Foundation, Inc.
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3 dnl This file is free software; the Free Software Foundation
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4 dnl gives unlimited permission to copy and/or distribute it,
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5 dnl with or without modifications, as long as this notice is preserved.
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6 AC_DEFUN([gl_FLOAT_EXPONENT_LOCATION],
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7 [
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8 AC_CACHE_CHECK([where to find the exponent in a 'float'],
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9 [gl_cv_cc_float_expbit0],
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10 [
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11 AC_TRY_RUN([
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12 #include <float.h>
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13 #include <stddef.h>
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14 #include <stdio.h>
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15 #include <string.h>
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16 #define NWORDS \
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17 ((sizeof (float) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
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18 typedef union { float value; unsigned int word[NWORDS]; } memory_float;
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19 static unsigned int ored_words[NWORDS];
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20 static unsigned int anded_words[NWORDS];
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21 static void add_to_ored_words (float x)
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22 {
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23 memory_float m;
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24 size_t i;
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25 /* Clear it first, in case
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26 sizeof (float) < sizeof (memory_float). */
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27 memset (&m, 0, sizeof (memory_float));
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28 m.value = x;
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29 for (i = 0; i < NWORDS; i++)
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30 {
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31 ored_words[i] |= m.word[i];
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32 anded_words[i] &= m.word[i];
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33 }
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34 }
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35 int main ()
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36 {
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37 size_t j;
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38 FILE *fp = fopen ("conftest.out", "w");
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39 if (fp == NULL)
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40 return 1;
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41 for (j = 0; j < NWORDS; j++)
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42 anded_words[j] = ~ (unsigned int) 0;
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43 add_to_ored_words (0.25f);
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44 add_to_ored_words (0.5f);
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45 add_to_ored_words (1.0f);
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46 add_to_ored_words (2.0f);
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47 add_to_ored_words (4.0f);
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48 /* Remove bits that are common (e.g. if representation of the first mantissa
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49 bit is explicit). */
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50 for (j = 0; j < NWORDS; j++)
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51 ored_words[j] &= ~anded_words[j];
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52 /* Now find the nonzero word. */
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53 for (j = 0; j < NWORDS; j++)
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54 if (ored_words[j] != 0)
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55 break;
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56 if (j < NWORDS)
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57 {
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58 size_t i;
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59 for (i = j + 1; i < NWORDS; i++)
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60 if (ored_words[i] != 0)
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61 {
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62 fprintf (fp, "unknown");
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63 return (fclose (fp) != 0);
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64 }
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65 for (i = 0; ; i++)
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66 if ((ored_words[j] >> i) & 1)
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67 {
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68 fprintf (fp, "word %d bit %d", (int) j, (int) i);
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69 return (fclose (fp) != 0);
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70 }
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71 }
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72 fprintf (fp, "unknown");
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73 return (fclose (fp) != 0);
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74 }
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75 ],
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76 [gl_cv_cc_float_expbit0=`cat conftest.out`],
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77 [gl_cv_cc_float_expbit0="unknown"],
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78 [gl_cv_cc_float_expbit0="word 0 bit 23"])
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79 rm -f conftest.out
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80 ])
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81 case "$gl_cv_cc_float_expbit0" in
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82 word*bit*)
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83 word=`echo "$gl_cv_cc_float_expbit0" | sed -e 's/word //' -e 's/ bit.*//'`
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84 bit=`echo "$gl_cv_cc_float_expbit0" | sed -e 's/word.*bit //'`
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85 AC_DEFINE_UNQUOTED([FLT_EXPBIT0_WORD], [$word],
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86 [Define as the word index where to find the exponent of 'float'.])
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87 AC_DEFINE_UNQUOTED([FLT_EXPBIT0_BIT], [$bit],
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88 [Define as the bit index in the word where to find bit 0 of the exponent of 'float'.])
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89 ;;
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90 esac
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91 ])