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Annotation of embedaddon/curl/m4/ax_compile_check_sizeof.m4, revision 1.1.1.1

1.1       misho       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: ])