This provides a simple ARRAY_SIZE() macro, which (given a good compiler) will also break compile if you try to use it on a pointer. This can ensure your code is robust to changes, without needing a gratuitous macro or constant. Credits to Rusty Russell (http://ccan.ozlabs.org/info/array_size.html) Having a util.h file, this kind of things can be shared among all users and we can remove all the declarations of ARRAY_SIZE. --- acinclude.m4 | 22 ++++++++++++++++++++++ configure.ac | 1 + src/util.h | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 78 insertions(+), 0 deletions(-) create mode 100644 src/util.h diff --git a/acinclude.m4 b/acinclude.m4 index a37959a..8c2ae92 100644 --- a/acinclude.m4 +++ b/acinclude.m4 @@ -31,6 +31,28 @@ AC_DEFUN([AC_FUNC_PPOLL], [ [Define to 1 if you need the ppoll() function.])) ]) +AC_DEFUN([AC_FUNC_TYPES_COMPATIBLE_P], [ + AC_CACHE_CHECK([if compiler has __builtin_types_compatible_p function], + [cc_cv_func_types_compatible_p], + [ac_save_CFLAGS="$CFLAGS" + CFLAGS="$CFLAGS -Werror" + AC_COMPILE_IFELSE([AC_LANG_SOURCE( + [int some_function(); + int some_function() { + return __builtin_types_compatible_p(char *, int) ? 1 : 0; + }])], + [cc_cv_func_types_compatible_p=yes], + [cc_cv_func_types_compatible_p=no]) + CFLAGS="$ac_save_CFLAGS" + ]) + + AS_IF([test "x$cc_cv_func_types_compatible_p" = "xyes"], + [AC_DEFINE([SUPPORT__BUILTIN_TYPES_COMPATIBLE_P], 1, + [Define this if the compiler supports __builtin_types_compatible_p() function]) + $1], + [$2]) +]) + AC_DEFUN([AC_INIT_BLUEZ], [ AC_PREFIX_DEFAULT(/usr/local) diff --git a/configure.ac b/configure.ac index 223c9d1..fed730f 100644 --- a/configure.ac +++ b/configure.ac @@ -31,6 +31,7 @@ AC_DISABLE_STATIC AC_PROG_LIBTOOL AC_FUNC_PPOLL +AC_FUNC_TYPES_COMPATIBLE_P AC_CHECK_LIB(dl, dlopen, dummy=yes, AC_MSG_ERROR(dynamic linking loader is required)) diff --git a/src/util.h b/src/util.h new file mode 100644 index 0000000..2c8a554 --- /dev/null +++ b/src/util.h @@ -0,0 +1,55 @@ +/* + * + * BlueZ - Bluetooth protocol stack for Linux + * + * Copyright (C) 2011 Texas Instruments, Inc. + * + * + * 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, write to the Free Software + * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA + * + */ + +/** + * BUILD_ASSERT_OR_ZERO - assert a build-time dependency, as an expression. + * @cond: the compile-time condition which must be true. + * + * Your compile will fail if the condition isn't true, or can't be evaluated + * by the compiler. This can be used in an expression: its value is "0". + * + * Example: + * #define foo_to_char(foo) \ + * ((char *)(foo) \ + * + BUILD_ASSERT_OR_ZERO(offsetof(struct foo, string) == 0)) + */ +#define BUILD_ASSERT_OR_ZERO(cond) \ + (sizeof(char [1 - 2*!(cond)]) - 1) + +#if SUPPORT__BUILTIN_TYPES_COMPATIBLE_P +#define _array_size_chk(arr) \ + BUILD_ASSERT_OR_ZERO(!__builtin_types_compatible_p(typeof(arr), \ + typeof(&(arr)[0]))) +#else +#define _array_size_chk(arr) 0 +#endif + +/** + * ARRAY_SIZE - get the number of elements in a visible array + * @arr: the array whose size you want. + * + * This does not work on pointers, or arrays declared as [], or + * function parameters. With correct compiler support, such usage + * will cause a build error (see build_assert). + */ +#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + _array_size_chk(arr)) -- 1.7.6 -- To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
