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- # ===========================================================================
- # https://www.gnu.org/software/autoconf-archive/ax_c_compile_value.html
- # ===========================================================================
- #
- # SYNOPSIS
- #
- # AX_C_COMPILE_VALUE (COMPILE-VALUE, ALIAS, INCLUDES)
- #
- # DESCRIPTION
- #
- # The AX_C_COMPILE_VALUE macro determines a compile time value by
- # generating the object code and reading the value from the code. Static
- # data initializers like sizeof(int) are unavailable to preprocessor. The
- # macro calculates the values known to compiler's static initializer.
- #
- # Assumptions: The sought value should not exceed 65535. The shell
- # interpreter and the sed utility are expected to exist and work similarly
- # across possible build platforms.
- #
- # Result: The resulting configure script will generate the preprocessor
- # symbol definition:
- #
- # #define COMPILE_VALUE_<ALIAS> <NUMBER>
- #
- # It was important that the value was embedded into the object file in a
- # predefined byte order during the test. This ensured that the result was
- # independent from the target platform's byte order.
- #
- # The existing AC_CHECK_SIZEOF macro also computes the size of the given
- # type without running the test program. However, the existing macro will
- # produce a piece of configure script that will take the time proportional
- # to the logarithm of the sought value.
- #
- # Example of use in configure.in:
- #
- # AX_C_COMPILE_VALUE(sizeof(int), sizeof_int)
- # AX_C_COMPILE_VALUE([sizeof(int[[543]])], sizeof_int543)
- #
- # As a result of running the generated configure script, the following
- # definition will appear in config.h:
- #
- # #define COMPILE_VALUE_SIZEOF_INT 4
- # #define COMPILE_VALUE_SIZEOF_INT543 2172
- #
- # LICENSE
- #
- # Copyright (c) 2008 Ilguiz Latypov
- #
- # This program is free software; you can redistribute it and/or modify it
- # under the terms of the GNU General Public License as published by the
- # Free Software Foundation; either version 2 of the License, or (at your
- # option) any later version.
- #
- # This program is distributed in the hope that it will be useful, but
- # WITHOUT ANY WARRANTY; without even the implied warranty of
- # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
- # Public License for more details.
- #
- # You should have received a copy of the GNU General Public License along
- # with this program. If not, see <https://www.gnu.org/licenses/>.
- #
- # As a special exception, the respective Autoconf Macro's copyright owner
- # gives unlimited permission to copy, distribute and modify the configure
- # scripts that are the output of Autoconf when processing the Macro. You
- # need not follow the terms of the GNU General Public License when using
- # or distributing such scripts, even though portions of the text of the
- # Macro appear in them. The GNU General Public License (GPL) does govern
- # all other use of the material that constitutes the Autoconf Macro.
- #
- # This special exception to the GPL applies to versions of the Autoconf
- # Macro released by the Autoconf Archive. When you make and distribute a
- # modified version of the Autoconf Macro, you may extend this special
- # exception to the GPL to apply to your modified version as well.
-
- #serial 7
-
- ## Portability defines that help interoperate with classic and modern autoconfs
- ifdef([AC_TR_SH],[
- define([AC_TR_SH_REUSE],[AC_TR_SH([$1])])
- define([AC_TR_CPP_REUSE],[AC_TR_CPP([$1])])
- ], [
- define([AC_TR_SH_REUSE],
- [patsubst(translit([[$1]], [*+], [pp]), [[^a-zA-Z0-9_]], [_])])
- define([AC_TR_CPP_REUSE],
- [patsubst(translit([[$1]],
- [*abcdefghijklmnopqrstuvwxyz],
- [PABCDEFGHIJKLMNOPQRSTUVWXYZ]),
- [[^A-Z0-9_]], [_])])
- ])
-
- AC_DEFUN([AX_C_COMPILE_VALUE], [
- pushdef([ac_c_compile_value],
- AC_TR_SH_REUSE([ac_cv_c_compile_value_$2]))dnl
- ac_c_compile_value_expand="$1"
- AC_CACHE_CHECK([value of $1 by analyzing object code],
- ac_c_compile_value, [
- save_CFLAGS="$CFLAGS"
- CFLAGS="$CFLAGS -c -o conftest.o"
- AC_TRY_COMPILE([$3
- #include <stddef.h>
- #include <stdint.h>
- #include <stdlib.h>
- #define COMPILE_VALUE $ac_c_compile_value_expand
- #define HEX_DIGIT(n) ((n) >= 10 ? 'a' + (n) - 10 : '0' + (n))
- char object_code_block[] = {
- '\n', 'e', '4', 'V', 'A',
- '0', 'x',
- (char) HEX_DIGIT((((COMPILE_VALUE / 16) / 16) / 16) % 16),
- (char) HEX_DIGIT(((COMPILE_VALUE / 16) / 16) % 16),
- (char) HEX_DIGIT((COMPILE_VALUE / 16) % 16),
- (char) HEX_DIGIT(COMPILE_VALUE % 16),
- 'Y', '3', 'p', 'M', '\n'
- };],
- [],
- [ac_c_compile_value=`
- typeset -i n=\`sed -ne 's/^e4VA0x\(.*\)Y3pM$/0x\1/p' < conftest.o\`;
- echo $n`],
- [ac_c_compile_value=0])
- CFLAGS="$save_CFLAGS"])
- AC_DEFINE_UNQUOTED(AC_TR_CPP_REUSE(compile_value_$2),
- [$[]ac_c_compile_value],
- [$1])
- popdef([ac_c_compile_value])dnl
- ])
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