[PATCH] btrfs-progs: fix compile warning when using gcc8 to compile btrfs-progs

[PATCH] btrfs-progs: fix compile warning when using gcc8 to compile btrfs-progs

[Su Yanjun]

When using gcc8 to compile btrfs-progs, it complains as below:

ctree.c: In function 'btrfs_search_slot_for_read':
    ctree.c:1249:45: warning: passing argument 3 of 'btrfs_search_slot'
    discards 'const' qualifier from pointer target type
    [-Wdiscarded-qualifiers]
             ret = btrfs_search_slot(NULL, root, key, p, 0, 0);

Change btrfs_search_slot prototype with 'const' qualifier for argument 3.
Also fix similar problems as above change.

Signed-off-by: Su Yanjun <suyj.fnst@cn.fujitsu.com>
---
 ctree.c | 19 ++++++++++---------
 ctree.h | 10 +++++-----
 2 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/ctree.c b/ctree.c
index aa1568620205..c8dd73cf2ce2 100644
--- a/ctree.c
+++ b/ctree.c
@@ -27,7 +27,7 @@
 static int split_node(struct btrfs_trans_handle *trans, struct btrfs_root
 		      *root, struct btrfs_path *path, int level);
 static int split_leaf(struct btrfs_trans_handle *trans, struct btrfs_root
-		      *root, struct btrfs_key *ins_key,
+		      *root, const struct btrfs_key *ins_key,
 		      struct btrfs_path *path, int data_size, int extend);
 static int push_node_left(struct btrfs_trans_handle *trans,
 			  struct btrfs_root *root, struct extent_buffer *dst,
@@ -389,7 +389,7 @@ int btrfs_cow_block(struct btrfs_trans_handle *trans,
 	return ret;
 }
 
-int btrfs_comp_cpu_keys(struct btrfs_key *k1, struct btrfs_key *k2)
+int btrfs_comp_cpu_keys(const struct btrfs_key *k1, const struct btrfs_key *k2)
 {
 	if (k1->objectid > k2->objectid)
 		return 1;
@@ -409,7 +409,8 @@ int btrfs_comp_cpu_keys(struct btrfs_key *k1, struct btrfs_key *k2)
 /*
  * compare two keys in a memcmp fashion
  */
-static int btrfs_comp_keys(struct btrfs_disk_key *disk, struct btrfs_key *k2)
+static int btrfs_comp_keys(struct btrfs_disk_key *disk,
+		const struct btrfs_key *k2)
 {
 	struct btrfs_key k1;
 
@@ -602,7 +603,7 @@ static int noinline check_block(struct btrfs_root *root,
  * slot may point to max if the key is bigger than all of the keys
  */
 static int generic_bin_search(struct extent_buffer *eb, unsigned long p,
-			      int item_size, struct btrfs_key *key,
+			      int item_size, const struct btrfs_key *key,
 			      int max, int *slot)
 {
 	int low = 0;
@@ -636,7 +637,7 @@ static int generic_bin_search(struct extent_buffer *eb, unsigned long p,
  * simple bin_search frontend that does the right thing for
  * leaves vs nodes
  */
-static int bin_search(struct extent_buffer *eb, struct btrfs_key *key,
+static int bin_search(struct extent_buffer *eb, const struct btrfs_key *key,
 		      int level, int *slot)
 {
 	if (level == 0)
@@ -1129,9 +1130,9 @@ out:
  * tree.  if ins_len < 0, nodes will be merged as we walk down the tree (if
  * possible)
  */
-int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root
-		      *root, struct btrfs_key *key, struct btrfs_path *p, int
-		      ins_len, int cow)
+int btrfs_search_slot(struct btrfs_trans_handle *trans,
+		struct btrfs_root *root, const struct btrfs_key *key,
+		struct btrfs_path *p, int ins_len, int cow)
 {
 	struct extent_buffer *b;
 	int slot;
@@ -2150,7 +2151,7 @@ static noinline int copy_for_split(struct btrfs_trans_handle *trans,
  */
 static noinline int split_leaf(struct btrfs_trans_handle *trans,
 			       struct btrfs_root *root,
-			       struct btrfs_key *ins_key,
+			       const struct btrfs_key *ins_key,
 			       struct btrfs_path *path, int data_size,
 			       int extend)
 {
diff --git a/ctree.h b/ctree.h
index 2a2437070ef9..cf0efae9c185 100644
--- a/ctree.h
+++ b/ctree.h
@@ -1973,7 +1973,7 @@ static inline void btrfs_disk_key_to_cpu(struct btrfs_key *cpu,
 }
 
 static inline void btrfs_cpu_key_to_disk(struct btrfs_disk_key *disk,
-					 struct btrfs_key *cpu)
+					 const struct btrfs_key *cpu)
 {
 	disk->offset = cpu_to_le64(cpu->offset);
 	disk->type = cpu->type;
@@ -2552,7 +2552,7 @@ u64 add_new_free_space(struct btrfs_block_group_cache *block_group,
 u64 hash_extent_data_ref(u64 root_objectid, u64 owner, u64 offset);
 
 /* ctree.c */
-int btrfs_comp_cpu_keys(struct btrfs_key *k1, struct btrfs_key *k2);
+int btrfs_comp_cpu_keys(const struct btrfs_key *k1, const struct btrfs_key *k2);
 int btrfs_del_ptr(struct btrfs_root *root, struct btrfs_path *path,
 		int level, int slot);
 enum btrfs_tree_block_status
@@ -2595,9 +2595,9 @@ int btrfs_split_item(struct btrfs_trans_handle *trans,
 		     struct btrfs_path *path,
 		     struct btrfs_key *new_key,
 		     unsigned long split_offset);
-int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root
-		      *root, struct btrfs_key *key, struct btrfs_path *p, int
-		      ins_len, int cow);
+int btrfs_search_slot(struct btrfs_trans_handle *trans,
+		struct btrfs_root *root, const struct btrfs_key *key,
+		struct btrfs_path *p, int ins_len, int cow);
 int btrfs_search_slot_for_read(struct btrfs_root *root,
                                const struct btrfs_key *key,
                                struct btrfs_path *p, int find_higher,
-- 
2.19.1

Re: [PATCH] btrfs-progs: fix compile warning when using gcc8 to compile btrfs-progs

[David Sterba]

On Fri, Oct 12, 2018 at 03:41:53PM +0800, Su Yanjun wrote:
> When using gcc8 to compile btrfs-progs, it complains as below:
> 
> ctree.c: In function 'btrfs_search_slot_for_read':
>     ctree.c:1249:45: warning: passing argument 3 of 'btrfs_search_slot'
>     discards 'const' qualifier from pointer target type
>     [-Wdiscarded-qualifiers]
>              ret = btrfs_search_slot(NULL, root, key, p, 0, 0);
> 
> Change btrfs_search_slot prototype with 'const' qualifier for argument 3.
> Also fix similar problems as above change.
> 
> Signed-off-by: Su Yanjun <suyj.fnst@cn.fujitsu.com>

Applied with subject line changed, thanks.

Re: [PATCH] btrfs-progs: fix compile warning when using gcc8 to compile btrfs-progs

[David Sterba]

On Fri, Oct 12, 2018 at 09:36:37AM +0800, Su Yanjun wrote:
> When using gcc8 compiles utils.c, it complains as below:
> 
> utils.c:852:45: warning: '%s' directive output may be truncated writing
> up to 4095 bytes into a region of size 4084 [-Wformat-truncation=]
>    snprintf(path, sizeof(path), "/dev/mapper/%s", name);
>                                              ^~   ~~~~
> In file included from /usr/include/stdio.h:873,
>                  from utils.c:20:
> /usr/include/bits/stdio2.h:67:10: note: '__builtin___snprintf_chk'
> output between 13 and 4108 bytes into a destination of size 4096
>    return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
>           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>         __bos (__s), __fmt, __va_arg_pack ());
>         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> This isn't a type of warning we care about, particularly when PATH_MAX
> is much less than either.
> 
> Using the GCC option -Wno-format-truncation to disable this.

Disabling for the default build is probably ok, but I'd rather keep the
warning in the extended set that's defined in Makefile.extrawarn. Please
update the patch and also pick a more specific subject line, there's
another patch with exactly same text but completely different set of
changes. Thanks.

[PATCH] btrfs-progs: fix compile warning when using gcc8 to compile btrfs-progs

[Su Yanjun]

When using gcc8 compiles utils.c, it complains as below:

utils.c:852:45: warning: '%s' directive output may be truncated writing
up to 4095 bytes into a region of size 4084 [-Wformat-truncation=]
   snprintf(path, sizeof(path), "/dev/mapper/%s", name);
                                             ^~   ~~~~
In file included from /usr/include/stdio.h:873,
                 from utils.c:20:
/usr/include/bits/stdio2.h:67:10: note: '__builtin___snprintf_chk'
output between 13 and 4108 bytes into a destination of size 4096
   return __builtin___snprintf_chk (__s, __n, __USE_FORTIFY_LEVEL - 1,
          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        __bos (__s), __fmt, __va_arg_pack ());
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This isn't a type of warning we care about, particularly when PATH_MAX
is much less than either.

Using the GCC option -Wno-format-truncation to disable this.

Signed-off-by: Su Yanjun <suyj.fnst@cn.fujitsu.com>
---
 configure.ac | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index df02f20655d9..c626beca8b77 100644
--- a/configure.ac
+++ b/configure.ac
@@ -12,7 +12,7 @@ LIBBTRFS_MAJOR=0
 LIBBTRFS_MINOR=1
 LIBBTRFS_PATCHLEVEL=2
 
-CFLAGS=${CFLAGS:-"-g -O1 -Wall -D_FORTIFY_SOURCE=2"}
+CFLAGS=${CFLAGS:-"-g -O1 -Wall -D_FORTIFY_SOURCE=2 -Wno-format-truncation"}
 AC_SUBST([CFLAGS])
 
 AC_PREREQ([2.60])
-- 
2.19.1