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
Hi Marcel,
On Fri, Jul 1, 2011 at 6:59 PM, Marcel Holtmann <[email protected]> wrote:
>
> Hi Lucas,
>
> > 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
>
> I am not sure that I actually want this. Where are the use cases of
> ARRAY_SIZE actually. Maybe we should just change them with proper NULL
> terminated arrays or other constants.
The uses cases are in the second patch. I added this because I was
going to use it for the AVRCP patches.
Why do you prefer NULL terminated arrays in case the content is static?
Regards,
Lucas De Marchi
Hi Lucas,
> 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
I am not sure that I actually want this. Where are the use cases of
ARRAY_SIZE actually. Maybe we should just change them with proper NULL
terminated arrays or other constants.
Regards
Marcel
---
audio/ipc.c | 3 +--
audio/pcm_bluetooth.c | 13 ++++++-------
lib/sdp.c | 3 +--
test/ipctest.c | 3 +--
4 files changed, 9 insertions(+), 13 deletions(-)
diff --git a/audio/ipc.c b/audio/ipc.c
index 1bdad78..cf4e8e4 100644
--- a/audio/ipc.c
+++ b/audio/ipc.c
@@ -21,8 +21,7 @@
*/
#include "ipc.h"
-
-#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
+#include "util.h"
/* This table contains the string representation for messages types */
static const char *strtypes[] = {
diff --git a/audio/pcm_bluetooth.c b/audio/pcm_bluetooth.c
index e633d1a..b20c653 100644
--- a/audio/pcm_bluetooth.c
+++ b/audio/pcm_bluetooth.c
@@ -43,6 +43,7 @@
#include "ipc.h"
#include "sbc.h"
#include "rtp.h"
+#include "util.h"
/* #define ENABLE_DEBUG */
@@ -1213,8 +1214,6 @@ static snd_pcm_ioplug_callback_t bluetooth_a2dp_capture = {
.poll_revents = bluetooth_poll_revents,
};
-#define ARRAY_NELEMS(a) (sizeof((a)) / sizeof((a)[0]))
-
static int bluetooth_hsp_hw_constraint(snd_pcm_ioplug_t *io)
{
struct bluetooth_data *data = io->private_data;
@@ -1232,13 +1231,13 @@ static int bluetooth_hsp_hw_constraint(snd_pcm_ioplug_t *io)
/* access type */
err = snd_pcm_ioplug_set_param_list(io, SND_PCM_IOPLUG_HW_ACCESS,
- ARRAY_NELEMS(access_list), access_list);
+ ARRAY_SIZE(access_list), access_list);
if (err < 0)
return err;
/* supported formats */
err = snd_pcm_ioplug_set_param_list(io, SND_PCM_IOPLUG_HW_FORMAT,
- ARRAY_NELEMS(format_list), format_list);
+ ARRAY_SIZE(format_list), format_list);
if (err < 0)
return err;
@@ -1294,13 +1293,13 @@ static int bluetooth_a2dp_hw_constraint(snd_pcm_ioplug_t *io)
/* access type */
err = snd_pcm_ioplug_set_param_list(io, SND_PCM_IOPLUG_HW_ACCESS,
- ARRAY_NELEMS(access_list), access_list);
+ ARRAY_SIZE(access_list), access_list);
if (err < 0)
return err;
/* supported formats */
err = snd_pcm_ioplug_set_param_list(io, SND_PCM_IOPLUG_HW_FORMAT,
- ARRAY_NELEMS(format_list), format_list);
+ ARRAY_SIZE(format_list), format_list);
if (err < 0)
return err;
@@ -1335,7 +1334,7 @@ static int bluetooth_a2dp_hw_constraint(snd_pcm_ioplug_t *io)
/* supported block sizes: */
err = snd_pcm_ioplug_set_param_list(io, SND_PCM_IOPLUG_HW_PERIOD_BYTES,
- ARRAY_NELEMS(period_list), period_list);
+ ARRAY_SIZE(period_list), period_list);
if (err < 0)
return err;
diff --git a/lib/sdp.c b/lib/sdp.c
index a48ee14..7f94cd9 100644
--- a/lib/sdp.c
+++ b/lib/sdp.c
@@ -48,12 +48,11 @@
#include "l2cap.h"
#include "sdp.h"
#include "sdp_lib.h"
+#include "util.h"
#define SDPINF(fmt, arg...) syslog(LOG_INFO, fmt "\n", ## arg)
#define SDPERR(fmt, arg...) syslog(LOG_ERR, "%s: " fmt "\n", __func__ , ## arg)
-#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
-
#ifdef SDP_DEBUG
#define SDPDBG(fmt, arg...) syslog(LOG_DEBUG, "%s: " fmt "\n", __func__ , ## arg)
#else
diff --git a/test/ipctest.c b/test/ipctest.c
index 9fdfac4..33801ba 100644
--- a/test/ipctest.c
+++ b/test/ipctest.c
@@ -42,14 +42,13 @@
#include "ipc.h"
#include "sbc.h"
+#include "util.h"
#define DBG(fmt, arg...) \
printf("debug %s: " fmt "\n" , __FUNCTION__ , ## arg)
#define ERR(fmt, arg...) \
fprintf(stderr, "ERROR %s: " fmt "\n" , __FUNCTION__ , ## arg)
-#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]))
-
#ifndef MIN
# define MIN(x, y) ((x) < (y) ? (x) : (y))
#endif
--
1.7.6