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    1: # ============================================================================
    2: #  https://www.gnu.org/software/autoconf-archive/ax_compile_check_sizeof.html
    3: # ============================================================================
    4: #
    5: # SYNOPSIS
    6: #
    7: #   AX_COMPILE_CHECK_SIZEOF(TYPE [, HEADERS [, EXTRA_SIZES...]])
    8: #
    9: # DESCRIPTION
   10: #
   11: #   This macro checks for the size of TYPE using compile checks, not run
   12: #   checks. You can supply extra HEADERS to look into. the check will cycle
   13: #   through 1 2 4 8 16 and any EXTRA_SIZES the user supplies. If a match is
   14: #   found, it will #define SIZEOF_`TYPE' to that value. Otherwise it will
   15: #   emit a configure time error indicating the size of the type could not be
   16: #   determined.
   17: #
   18: #   The trick is that C will not allow duplicate case labels. While this is
   19: #   valid C code:
   20: #
   21: #     switch (0) case 0: case 1:;
   22: #
   23: #   The following is not:
   24: #
   25: #     switch (0) case 0: case 0:;
   26: #
   27: #   Thus, the AC_TRY_COMPILE will fail if the currently tried size does not
   28: #   match.
   29: #
   30: #   Here is an example skeleton configure.in script, demonstrating the
   31: #   macro's usage:
   32: #
   33: #     AC_PROG_CC
   34: #     AC_CHECK_HEADERS(stddef.h unistd.h)
   35: #     AC_TYPE_SIZE_T
   36: #     AC_CHECK_TYPE(ssize_t, int)
   37: #
   38: #     headers='#ifdef HAVE_STDDEF_H
   39: #     #include <stddef.h>
   40: #     #endif
   41: #     #ifdef HAVE_UNISTD_H
   42: #     #include <unistd.h>
   43: #     #endif
   44: #     '
   45: #
   46: #     AX_COMPILE_CHECK_SIZEOF(char)
   47: #     AX_COMPILE_CHECK_SIZEOF(short)
   48: #     AX_COMPILE_CHECK_SIZEOF(int)
   49: #     AX_COMPILE_CHECK_SIZEOF(long)
   50: #     AX_COMPILE_CHECK_SIZEOF(unsigned char *)
   51: #     AX_COMPILE_CHECK_SIZEOF(void *)
   52: #     AX_COMPILE_CHECK_SIZEOF(size_t, $headers)
   53: #     AX_COMPILE_CHECK_SIZEOF(ssize_t, $headers)
   54: #     AX_COMPILE_CHECK_SIZEOF(ptrdiff_t, $headers)
   55: #     AX_COMPILE_CHECK_SIZEOF(off_t, $headers)
   56: #
   57: # LICENSE
   58: #
   59: #   Copyright (c) 2008 Kaveh Ghazi <ghazi@caip.rutgers.edu>
   60: #   Copyright (c) 2017 Reini Urban <rurban@cpan.org>
   61: #
   62: #   This program is free software: you can redistribute it and/or modify it
   63: #   under the terms of the GNU General Public License as published by the
   64: #   Free Software Foundation, either version 3 of the License, or (at your
   65: #   option) any later version.
   66: #
   67: #   This program is distributed in the hope that it will be useful, but
   68: #   WITHOUT ANY WARRANTY; without even the implied warranty of
   69: #   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
   70: #   Public License for more details.
   71: #
   72: #   You should have received a copy of the GNU General Public License along
   73: #   with this program. If not, see <https://www.gnu.org/licenses/>.
   74: #
   75: #   As a special exception, the respective Autoconf Macro's copyright owner
   76: #   gives unlimited permission to copy, distribute and modify the configure
   77: #   scripts that are the output of Autoconf when processing the Macro. You
   78: #   need not follow the terms of the GNU General Public License when using
   79: #   or distributing such scripts, even though portions of the text of the
   80: #   Macro appear in them. The GNU General Public License (GPL) does govern
   81: #   all other use of the material that constitutes the Autoconf Macro.
   82: #
   83: #   This special exception to the GPL applies to versions of the Autoconf
   84: #   Macro released by the Autoconf Archive. When you make and distribute a
   85: #   modified version of the Autoconf Macro, you may extend this special
   86: #   exception to the GPL to apply to your modified version as well.
   87: 
   88: #serial 7
   89: 
   90: AU_ALIAS([AC_COMPILE_CHECK_SIZEOF], [AX_COMPILE_CHECK_SIZEOF])
   91: AC_DEFUN([AX_COMPILE_CHECK_SIZEOF],
   92: [changequote(<<, >>)dnl
   93: dnl The name to #define.
   94: define(<<AC_TYPE_NAME>>, translit(sizeof_$1, [a-z *], [A-Z_P]))dnl
   95: dnl The cache variable name.
   96: define(<<AC_CV_NAME>>, translit(ac_cv_sizeof_$1, [ *], [_p]))dnl
   97: changequote([, ])dnl
   98: AC_MSG_CHECKING(size of $1)
   99: AC_CACHE_VAL(AC_CV_NAME,
  100: [for ac_size in 4 8 1 2 16 $3 ; do # List sizes in rough order of prevalence.
  101:   AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
  102: #include <sys/types.h>
  103: $2
  104: ]], [[switch (0) case 0: case (sizeof ($1) == $ac_size):;]])], [AC_CV_NAME=$ac_size])
  105:   if test x$AC_CV_NAME != x ; then break; fi
  106: done
  107: ])
  108: if test x$AC_CV_NAME = x ; then
  109:   AC_MSG_ERROR([cannot determine a size for $1])
  110: fi
  111: AC_MSG_RESULT($AC_CV_NAME)
  112: AC_DEFINE_UNQUOTED(AC_TYPE_NAME, $AC_CV_NAME, [The number of bytes in type $1])
  113: undefine([AC_TYPE_NAME])dnl
  114: undefine([AC_CV_NAME])dnl
  115: ])