1 | # size_max.m4 serial 5 |
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2 | dnl Copyright (C) 2003, 2005-2006 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 | |
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7 | dnl From Bruno Haible. |
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8 | |
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9 | AC_DEFUN([gl_SIZE_MAX], |
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10 | [ |
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11 | AC_CHECK_HEADERS(stdint.h) |
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12 | dnl First test whether the system already has SIZE_MAX. |
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13 | AC_MSG_CHECKING([for SIZE_MAX]) |
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14 | AC_CACHE_VAL([gl_cv_size_max], [ |
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15 | gl_cv_size_max= |
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16 | AC_EGREP_CPP([Found it], [ |
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17 | #include <limits.h> |
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18 | #if HAVE_STDINT_H |
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19 | #include <stdint.h> |
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20 | #endif |
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21 | #ifdef SIZE_MAX |
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22 | Found it |
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23 | #endif |
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24 | ], gl_cv_size_max=yes) |
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25 | if test -z "$gl_cv_size_max"; then |
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26 | dnl Define it ourselves. Here we assume that the type 'size_t' is not wider |
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27 | dnl than the type 'unsigned long'. Try hard to find a definition that can |
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28 | dnl be used in a preprocessor #if, i.e. doesn't contain a cast. |
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29 | _AC_COMPUTE_INT([sizeof (size_t) * CHAR_BIT - 1], size_t_bits_minus_1, |
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30 | [#include <stddef.h> |
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31 | #include <limits.h>], size_t_bits_minus_1=) |
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32 | _AC_COMPUTE_INT([sizeof (size_t) <= sizeof (unsigned int)], fits_in_uint, |
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33 | [#include <stddef.h>], fits_in_uint=) |
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34 | if test -n "$size_t_bits_minus_1" && test -n "$fits_in_uint"; then |
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35 | if test $fits_in_uint = 1; then |
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36 | dnl Even though SIZE_MAX fits in an unsigned int, it must be of type |
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37 | dnl 'unsigned long' if the type 'size_t' is the same as 'unsigned long'. |
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38 | AC_TRY_COMPILE([#include <stddef.h> |
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39 | extern size_t foo; |
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40 | extern unsigned long foo; |
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41 | ], [], fits_in_uint=0) |
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42 | fi |
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43 | dnl We cannot use 'expr' to simplify this expression, because 'expr' |
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44 | dnl works only with 'long' integers in the host environment, while we |
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45 | dnl might be cross-compiling from a 32-bit platform to a 64-bit platform. |
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46 | if test $fits_in_uint = 1; then |
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47 | gl_cv_size_max="(((1U << $size_t_bits_minus_1) - 1) * 2 + 1)" |
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48 | else |
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49 | gl_cv_size_max="(((1UL << $size_t_bits_minus_1) - 1) * 2 + 1)" |
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50 | fi |
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51 | else |
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52 | dnl Shouldn't happen, but who knows... |
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53 | gl_cv_size_max='((size_t)~(size_t)0)' |
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54 | fi |
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55 | fi |
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56 | ]) |
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57 | AC_MSG_RESULT([$gl_cv_size_max]) |
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58 | if test "$gl_cv_size_max" != yes; then |
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59 | AC_DEFINE_UNQUOTED([SIZE_MAX], [$gl_cv_size_max], |
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60 | [Define as the maximum value of type 'size_t', if the system doesn't define it.]) |
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61 | fi |
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62 | ]) |
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