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From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To: Jaroslav Kysela <perex@perex.cz>, Takashi Iwai <tiwai@suse.com>,
	Liam Girdwood <lgirdwood@gmail.com>,
	Mark Brown <broonie@kernel.org>,
	Clemens Ladisch <clemens@ladisch.de>,
	Takashi Sakamoto <o-takashi@sakamocchi.jp>,
	Cezary Rojewski <cezary.rojewski@intel.com>,
	Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>,
	Jie Yang <yang.jie@linux.intel.com>
Cc: alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org,
	"Gustavo A. R. Silva" <gustavo@embeddedor.com>
Subject: [PATCH] sound: Replace zero-length array with flexible-array member
Date: Thu, 20 Feb 2020 07:24:20 -0600	[thread overview]
Message-ID: <20200220132420.GA29765@embeddedor> (raw)

The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by
this change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 include/sound/control.h                  | 2 +-
 include/sound/intel-nhlt.h               | 6 +++---
 include/sound/soc-dapm.h                 | 2 +-
 include/sound/soc.h                      | 2 +-
 include/uapi/sound/asound.h              | 2 +-
 include/uapi/sound/skl-tplg-interface.h  | 2 +-
 sound/core/oss/pcm_plugin.h              | 2 +-
 sound/firewire/fireworks/fireworks.h     | 2 +-
 sound/soc/intel/atom/sst-atom-controls.h | 2 +-
 sound/soc/intel/skylake/skl-i2s.h        | 2 +-
 sound/soc/intel/skylake/skl-topology.h   | 4 ++--
 sound/soc/intel/skylake/skl.h            | 2 +-
 sound/usb/usx2y/usbusx2y.h               | 2 +-
 13 files changed, 16 insertions(+), 16 deletions(-)

diff --git a/include/sound/control.h b/include/sound/control.h
index 11feeee31e35..aeaed2a05bae 100644
--- a/include/sound/control.h
+++ b/include/sound/control.h
@@ -75,7 +75,7 @@ struct snd_kcontrol {
 	unsigned long private_value;
 	void *private_data;
 	void (*private_free)(struct snd_kcontrol *kcontrol);
-	struct snd_kcontrol_volatile vd[0];	/* volatile data */
+	struct snd_kcontrol_volatile vd[];	/* volatile data */
 };
 
 #define snd_kcontrol(n) list_entry(n, struct snd_kcontrol, list)
diff --git a/include/sound/intel-nhlt.h b/include/sound/intel-nhlt.h
index f657fd8fc0ad..743c2f442280 100644
--- a/include/sound/intel-nhlt.h
+++ b/include/sound/intel-nhlt.h
@@ -50,7 +50,7 @@ enum nhlt_device_type {
 
 struct nhlt_specific_cfg {
 	u32 size;
-	u8 caps[0];
+	u8 caps[];
 } __packed;
 
 struct nhlt_fmt_cfg {
@@ -60,7 +60,7 @@ struct nhlt_fmt_cfg {
 
 struct nhlt_fmt {
 	u8 fmt_count;
-	struct nhlt_fmt_cfg fmt_config[0];
+	struct nhlt_fmt_cfg fmt_config[];
 } __packed;
 
 struct nhlt_endpoint {
@@ -80,7 +80,7 @@ struct nhlt_endpoint {
 struct nhlt_acpi_table {
 	struct acpi_table_header header;
 	u8 endpoint_count;
-	struct nhlt_endpoint desc[0];
+	struct nhlt_endpoint desc[];
 } __packed;
 
 struct nhlt_resource_desc  {
diff --git a/include/sound/soc-dapm.h b/include/sound/soc-dapm.h
index 1a9c5dd40228..f870f927b70c 100644
--- a/include/sound/soc-dapm.h
+++ b/include/sound/soc-dapm.h
@@ -688,7 +688,7 @@ struct snd_soc_dapm_context {
 /* A list of widgets associated with an object, typically a snd_kcontrol */
 struct snd_soc_dapm_widget_list {
 	int num_widgets;
-	struct snd_soc_dapm_widget *widgets[0];
+	struct snd_soc_dapm_widget *widgets[];
 };
 
 #define for_each_dapm_widgets(list, i, widget)				\
diff --git a/include/sound/soc.h b/include/sound/soc.h
index f0e4f36f83bf..9944b978ae70 100644
--- a/include/sound/soc.h
+++ b/include/sound/soc.h
@@ -1146,7 +1146,7 @@ struct snd_soc_pcm_runtime {
 	unsigned int fe_compr:1; /* for Dynamic PCM */
 
 	int num_components;
-	struct snd_soc_component *components[0]; /* CPU/Codec/Platform */
+	struct snd_soc_component *components[]; /* CPU/Codec/Platform */
 };
 #define for_each_rtd_components(rtd, i, component)			\
 	for ((i) = 0;							\
diff --git a/include/uapi/sound/asound.h b/include/uapi/sound/asound.h
index 535a7229e1d9..3809993f6cb4 100644
--- a/include/uapi/sound/asound.h
+++ b/include/uapi/sound/asound.h
@@ -1071,7 +1071,7 @@ struct snd_ctl_elem_value {
 struct snd_ctl_tlv {
 	unsigned int numid;	/* control element numeric identification */
 	unsigned int length;	/* in bytes aligned to 4 */
-	unsigned int tlv[0];	/* first TLV */
+	unsigned int tlv[];	/* first TLV */
 };
 
 #define SNDRV_CTL_IOCTL_PVERSION	_IOR('U', 0x00, int)
diff --git a/include/uapi/sound/skl-tplg-interface.h b/include/uapi/sound/skl-tplg-interface.h
index 9eee32f5e407..62f76f154d19 100644
--- a/include/uapi/sound/skl-tplg-interface.h
+++ b/include/uapi/sound/skl-tplg-interface.h
@@ -149,7 +149,7 @@ struct skl_dfw_algo_data {
 	__u32 rsvd:30;
 	__u32 param_id;
 	__u32 max;
-	char params[0];
+	char params[];
 } __packed;
 
 enum skl_tkn_dir {
diff --git a/sound/core/oss/pcm_plugin.h b/sound/core/oss/pcm_plugin.h
index 8d2f7a4e3ab6..46e273bd4a78 100644
--- a/sound/core/oss/pcm_plugin.h
+++ b/sound/core/oss/pcm_plugin.h
@@ -64,7 +64,7 @@ struct snd_pcm_plugin {
 	char *buf;
 	snd_pcm_uframes_t buf_frames;
 	struct snd_pcm_plugin_channel *buf_channels;
-	char extra_data[0];
+	char extra_data[];
 };
 
 int snd_pcm_plugin_build(struct snd_pcm_substream *handle,
diff --git a/sound/firewire/fireworks/fireworks.h b/sound/firewire/fireworks/fireworks.h
index dda797209a27..654e28a6669f 100644
--- a/sound/firewire/fireworks/fireworks.h
+++ b/sound/firewire/fireworks/fireworks.h
@@ -177,7 +177,7 @@ struct snd_efw_phys_meters {
 	u32 in_meters;
 	u32 reserved4;
 	u32 reserved5;
-	u32 values[0];
+	u32 values[];
 } __packed;
 enum snd_efw_clock_source {
 	SND_EFW_CLOCK_SOURCE_INTERNAL	= 0,
diff --git a/sound/soc/intel/atom/sst-atom-controls.h b/sound/soc/intel/atom/sst-atom-controls.h
index 5356e954a732..620b48d2a064 100644
--- a/sound/soc/intel/atom/sst-atom-controls.h
+++ b/sound/soc/intel/atom/sst-atom-controls.h
@@ -410,7 +410,7 @@ struct sst_cmd_set_gain_dual {
 struct sst_cmd_set_params {
 	struct sst_destination_id dst;
 	u16 command_id;
-	char params[0];
+	char params[];
 } __packed;
 
 
diff --git a/sound/soc/intel/skylake/skl-i2s.h b/sound/soc/intel/skylake/skl-i2s.h
index d7c15873c0d4..dfce91e11be1 100644
--- a/sound/soc/intel/skylake/skl-i2s.h
+++ b/sound/soc/intel/skylake/skl-i2s.h
@@ -46,7 +46,7 @@ struct skl_i2s_config_mclk {
 struct skl_i2s_config_mclk_ext {
 	u32 mdivctrl;
 	u32 mdivr_count;
-	u32 mdivr[0];
+	u32 mdivr[];
 } __packed;
 
 struct skl_i2s_config_blob_signature {
diff --git a/sound/soc/intel/skylake/skl-topology.h b/sound/soc/intel/skylake/skl-topology.h
index e967800dbb62..d2cd8ef8e97f 100644
--- a/sound/soc/intel/skylake/skl-topology.h
+++ b/sound/soc/intel/skylake/skl-topology.h
@@ -119,7 +119,7 @@ struct skl_cpr_gtw_cfg {
 struct skl_dma_control {
 	u32 node_id;
 	u32 config_length;
-	u32 config_data[0];
+	u32 config_data[];
 } __packed;
 
 struct skl_cpr_cfg {
@@ -152,7 +152,7 @@ struct skl_up_down_mixer_cfg {
 
 struct skl_algo_cfg {
 	struct skl_base_cfg  base_cfg;
-	char params[0];
+	char params[];
 } __packed;
 
 struct skl_base_outfmt_cfg {
diff --git a/sound/soc/intel/skylake/skl.h b/sound/soc/intel/skylake/skl.h
index 2bfbf59277c4..26057f38a014 100644
--- a/sound/soc/intel/skylake/skl.h
+++ b/sound/soc/intel/skylake/skl.h
@@ -49,7 +49,7 @@ struct skl_astate_param {
 
 struct skl_astate_config {
 	u32 count;
-	struct skl_astate_param astate_table[0];
+	struct skl_astate_param astate_table[];
 };
 
 struct skl_fw_config {
diff --git a/sound/usb/usx2y/usbusx2y.h b/sound/usb/usx2y/usbusx2y.h
index e0f77172ce8f..144b85f57bd2 100644
--- a/sound/usb/usx2y/usbusx2y.h
+++ b/sound/usb/usx2y/usbusx2y.h
@@ -18,7 +18,7 @@ struct snd_usX2Y_AsyncSeq {
 struct snd_usX2Y_urbSeq {
 	int	submitted;
 	int	len;
-	struct urb	*urb[0];
+	struct urb	*urb[];
 };
 
 #include "usx2yhwdeppcm.h"
-- 
2.25.0


             reply	other threads:[~2020-02-20 13:21 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-20 13:24 Gustavo A. R. Silva [this message]
2020-02-20 18:45 ` [PATCH] sound: Replace zero-length array with flexible-array member Mark Brown
2020-02-20 18:45   ` Mark Brown
2020-02-20 18:52   ` Gustavo A. R. Silva
2020-02-20 18:52     ` Gustavo A. R. Silva

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