[PATCH] sound: Replace zero-length array with flexible-array member

From: Gustavo A. R. Silva
Date: Thu Feb 20 2020 - 08:21:41 EST

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@xxxxxxxxxxxxxx>
---
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