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From: Zdenek Kabelac <zkabelac@redhat.com>
To: LVM general discussion and development <linux-lvm@redhat.com>,
	"heming.zhao@suse.com" <heming.zhao@suse.com>
Subject: Re: [linux-lvm] [PATCH] gcc: change zero-sized array to fexlible array
Date: Fri, 28 Aug 2020 21:32:44 +0200	[thread overview]
Message-ID: <80e36f4c-8193-1df5-41ad-e0caf42f6537@redhat.com> (raw)
In-Reply-To: <ff41471a-d775-a314-434a-eac3fd0668a4@suse.com>

[-- Attachment #1: Type: text/plain, Size: 1306 bytes --]

Dne 26. 08. 20 v 7:18 heming.zhao@suse.com napsal(a):
> ping.
> 
> @Marian & other maintainers
> 
> 
> On 8/21/20 12:05 AM, Zhao Heming wrote:
>> this patch makes gcc happy with compiling option: [-Wstringop-overflow=]
>>
>> Signed-off-by: Zhao Heming <heming.zhao@suse.com>
>> ---
>>    device_mapper/libdm-common.c | 2 +-
>>    lib/activate/fs.c            | 2 +-
>>    libdm/libdm-common.c         | 2 +-
>>    3 files changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/device_mapper/libdm-common.c b/device_mapper/libdm-common.c
>> index bc691d6..3627457 100644
>> --- a/device_mapper/libdm-common.c
>> +++ b/device_mapper/libdm-common.c
>> @@ -1445,7 +1445,7 @@ struct node_op_parms {
>>    	char *old_name;
>>    	int warn_if_udev_failed;
>>    	unsigned rely_on_udev;
>> -	char names[0];
>> +	char names[];
>>    };
>>    


Hi

Here I don't see much problem with patch itself - except it seems to be 
somewhat mysterious. Lvm2 is not strict ISO C compilable - there are far to 
many other things which would need to be fixed - thus flexible arrays 
shouldn't be an issue.

I'm curious why these 3 were important in your case - while other 26 
appearances passed for you just fine (see attachment).

So can you paste what sort of gcc problem do you actually try to solve ?

Regards

Zdenek

[-- Attachment #2: gcc-change-zero-sized-array-to-fexlible-array-II.patch --]
[-- Type: text/x-patch, Size: 8301 bytes --]

From: Zdenek Kabelac <zkabelac@redhat.com>
Date: Fri, 28 Aug 2020 19:15:01 +0200
Subject:  gcc: change zero-sized array to fexlible array II

---
 base/data-struct/hash.c                | 2 +-
 base/data-struct/radix-tree-adaptive.c | 2 +-
 daemons/lvmlockd/lvmlockd-internal.h   | 2 +-
 device_mapper/all.h                    | 6 +++---
 device_mapper/misc/dm-ioctl.h          | 8 ++++----
 lib/device/dev-cache.c                 | 2 +-
 lib/format_text/layout.h               | 6 +++---
 lib/label/label.c                      | 2 +-
 lib/metadata/lv_manip.c                | 2 +-
 libdm/datastruct/hash.c                | 2 +-
 libdm/libdevmapper.h                   | 6 +++---
 libdm/libdm-stats.c                    | 2 +-
 libdm/misc/dm-ioctl.h                  | 8 ++++----
 tools/tools.h                          | 2 +-
 14 files changed, 26 insertions(+), 26 deletions(-)

diff --git a/base/data-struct/hash.c b/base/data-struct/hash.c
index 0a0541d2e..5ef5ed276 100644
--- a/base/data-struct/hash.c
+++ b/base/data-struct/hash.c
@@ -22,7 +22,7 @@ struct dm_hash_node {
 	void *data;
 	unsigned data_len;
 	unsigned keylen;
-	char key[0];
+	char key[];
 };
 
 struct dm_hash_table {
diff --git a/base/data-struct/radix-tree-adaptive.c b/base/data-struct/radix-tree-adaptive.c
index b9ba4179f..3a46cc14b 100644
--- a/base/data-struct/radix-tree-adaptive.c
+++ b/base/data-struct/radix-tree-adaptive.c
@@ -47,7 +47,7 @@ struct value_chain {
 struct prefix_chain {
 	struct value child;
 	unsigned len;
-	uint8_t prefix[0];
+	uint8_t prefix[];
 };
 
 struct node4 {
diff --git a/daemons/lvmlockd/lvmlockd-internal.h b/daemons/lvmlockd/lvmlockd-internal.h
index 191c44926..14bdfeed0 100644
--- a/daemons/lvmlockd/lvmlockd-internal.h
+++ b/daemons/lvmlockd/lvmlockd-internal.h
@@ -158,7 +158,7 @@ struct resource {
 	struct list_head locks;
 	struct list_head actions;
 	char lv_args[MAX_ARGS+1];
-	char lm_data[0];		/* lock manager specific data */
+	char lm_data[];			/* lock manager specific data */
 };
 
 #define LD_LF_PERSISTENT 0x00000001
diff --git a/device_mapper/all.h b/device_mapper/all.h
index c3c6219e3..ace3b69a0 100644
--- a/device_mapper/all.h
+++ b/device_mapper/all.h
@@ -164,20 +164,20 @@ struct dm_info {
 struct dm_deps {
 	uint32_t count;
 	uint32_t filler;
-	uint64_t device[0];
+	uint64_t device[];
 };
 
 struct dm_names {
 	uint64_t dev;
 	uint32_t next;		/* Offset to next struct from start of this struct */
-	char name[0];
+	char name[];
 };
 
 struct dm_versions {
 	uint32_t next;		/* Offset to next struct from start of this struct */
 	uint32_t version[3];
 
-	char name[0];
+	char name[];
 };
 
 int dm_get_library_version(char *version, size_t size);
diff --git a/device_mapper/misc/dm-ioctl.h b/device_mapper/misc/dm-ioctl.h
index cc2374c36..49954a764 100644
--- a/device_mapper/misc/dm-ioctl.h
+++ b/device_mapper/misc/dm-ioctl.h
@@ -183,7 +183,7 @@ struct dm_target_spec {
 struct dm_target_deps {
 	uint32_t count;	/* Array size */
 	uint32_t padding;	/* unused */
-	uint64_t dev[0];	/* out */
+	uint64_t dev[];		/* out */
 };
 
 /*
@@ -193,7 +193,7 @@ struct dm_name_list {
 	uint64_t dev;
 	uint32_t next;		/* offset to the next record from
 				   the _start_ of this */
-	char name[0];
+	char name[];
 };
 
 /*
@@ -203,7 +203,7 @@ struct dm_target_versions {
         uint32_t next;
         uint32_t version[3];
 
-        char name[0];
+        char name[];
 };
 
 /*
@@ -212,7 +212,7 @@ struct dm_target_versions {
 struct dm_target_msg {
 	uint64_t sector;	/* Device sector */
 
-	char message[0];
+	char message[];
 };
 
 /*
diff --git a/lib/device/dev-cache.c b/lib/device/dev-cache.c
index c3f7c49be..d4e2658aa 100644
--- a/lib/device/dev-cache.c
+++ b/lib/device/dev-cache.c
@@ -35,7 +35,7 @@ struct dev_iter {
 
 struct dir_list {
 	struct dm_list list;
-	char dir[0];
+	char dir[];
 };
 
 static struct {
diff --git a/lib/format_text/layout.h b/lib/format_text/layout.h
index c3dfe8e7a..df7ed3a78 100644
--- a/lib/format_text/layout.h
+++ b/lib/format_text/layout.h
@@ -33,7 +33,7 @@ struct pv_header_extension {
 	uint32_t version;
 	uint32_t flags;
 	/* NULL-terminated list of bootloader areas */
-	struct disk_locn bootloader_areas_xl[0];
+	struct disk_locn bootloader_areas_xl[];
 } __attribute__ ((packed));
 
 /* Fields with the suffix _xl should be xlate'd wherever they appear */
@@ -46,7 +46,7 @@ struct pv_header {
 
 	/* NULL-terminated list of data areas followed by */
 	/* NULL-terminated list of metadata area headers */
-	struct disk_locn disk_areas_xl[0];	/* Two lists */
+	struct disk_locn disk_areas_xl[];	/* Two lists */
 } __attribute__ ((packed));
 
 /*
@@ -76,7 +76,7 @@ struct mda_header {
 	uint64_t start;		/* Absolute start byte of mda_header */
 	uint64_t size;		/* Size of metadata area */
 
-	struct raw_locn raw_locns[0];	/* NULL-terminated list */
+	struct raw_locn raw_locns[];	/* NULL-terminated list */
 } __attribute__ ((packed));
 
 struct mda_header *raw_read_mda_header(const struct format_type *fmt,
diff --git a/lib/label/label.c b/lib/label/label.c
index 4d369d4f1..8e68f9303 100644
--- a/lib/label/label.c
+++ b/lib/label/label.c
@@ -43,7 +43,7 @@ struct labeller_i {
 	struct dm_list list;
 
 	struct labeller *l;
-	char name[0];
+	char name[];
 };
 
 static struct dm_list _labellers;
diff --git a/lib/metadata/lv_manip.c b/lib/metadata/lv_manip.c
index c47ec72e2..95ca2df39 100644
--- a/lib/metadata/lv_manip.c
+++ b/lib/metadata/lv_manip.c
@@ -1798,7 +1798,7 @@ struct alloc_handle {
 	 * Contains area_count lists of areas allocated to data stripes
 	 * followed by log_area_count lists of areas allocated to log stripes.
 	 */
-	struct dm_list alloced_areas[0];
+	struct dm_list alloced_areas[];
 };
 
 /*
diff --git a/libdm/datastruct/hash.c b/libdm/datastruct/hash.c
index 4c940039a..726347ea2 100644
--- a/libdm/datastruct/hash.c
+++ b/libdm/datastruct/hash.c
@@ -20,7 +20,7 @@ struct dm_hash_node {
 	void *data;
 	unsigned data_len;
 	unsigned keylen;
-	char key[0];
+	char key[];
 };
 
 struct dm_hash_table {
diff --git a/libdm/libdevmapper.h b/libdm/libdevmapper.h
index e9b140563..059b96f0b 100644
--- a/libdm/libdevmapper.h
+++ b/libdm/libdevmapper.h
@@ -165,20 +165,20 @@ struct dm_info {
 struct dm_deps {
 	uint32_t count;
 	uint32_t filler;
-	uint64_t device[0];
+	uint64_t device[];
 };
 
 struct dm_names {
 	uint64_t dev;
 	uint32_t next;		/* Offset to next struct from start of this struct */
-	char name[0];
+	char name[];
 };
 
 struct dm_versions {
 	uint32_t next;		/* Offset to next struct from start of this struct */
 	uint32_t version[3];
 
-	char name[0];
+	char name[];
 };
 
 int dm_get_library_version(char *version, size_t size);
diff --git a/libdm/libdm-stats.c b/libdm/libdm-stats.c
index 5379bed5e..f8d79d807 100644
--- a/libdm/libdm-stats.c
+++ b/libdm/libdm-stats.c
@@ -65,7 +65,7 @@ struct dm_histogram {
 	const struct dm_stats_region *region;
 	uint64_t sum; /* Sum of histogram bin counts. */
 	int nr_bins; /* Number of histogram bins assigned. */
-	struct dm_histogram_bin bins[0];
+	struct dm_histogram_bin bins[];
 };
 
 /*
diff --git a/libdm/misc/dm-ioctl.h b/libdm/misc/dm-ioctl.h
index 52a7a93d1..55dee2148 100644
--- a/libdm/misc/dm-ioctl.h
+++ b/libdm/misc/dm-ioctl.h
@@ -183,7 +183,7 @@ struct dm_target_spec {
 struct dm_target_deps {
 	uint32_t count;	/* Array size */
 	uint32_t padding;	/* unused */
-	uint64_t dev[0];	/* out */
+	uint64_t dev[];		/* out */
 };
 
 /*
@@ -193,7 +193,7 @@ struct dm_name_list {
 	uint64_t dev;
 	uint32_t next;		/* offset to the next record from
 				   the _start_ of this */
-	char name[0];
+	char name[];
 };
 
 /*
@@ -203,7 +203,7 @@ struct dm_target_versions {
         uint32_t next;
         uint32_t version[3];
 
-        char name[0];
+        char name[];
 };
 
 /*
@@ -212,7 +212,7 @@ struct dm_target_versions {
 struct dm_target_msg {
 	uint64_t sector;	/* Device sector */
 
-	char message[0];
+	char message[];
 };
 
 /*
diff --git a/tools/tools.h b/tools/tools.h
index 4b944e2fd..befff5708 100644
--- a/tools/tools.h
+++ b/tools/tools.h
@@ -110,7 +110,7 @@ struct arg_values {
 struct arg_value_group_list {
         struct dm_list list;
 	uint32_t prio;
-        struct arg_values arg_values[0];
+	struct arg_values arg_values[];
 };
 
 #define PERMITTED_READ_ONLY 	0x00000002
-- 
2.27.0


  reply	other threads:[~2020-08-28 19:32 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-20 16:05 Zhao Heming
2020-08-20 16:08 ` heming.zhao
2020-08-26  5:18 ` heming.zhao
2020-08-28 19:32   ` Zdenek Kabelac [this message]
2020-08-29  3:11     ` heming.zhao
2020-09-02 15:22       ` Zdenek Kabelac
2020-09-03 14:58         ` heming.zhao

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