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: ])
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