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]
sizeof(flexible-array-member) triggers a warning because flexible array
members have incomplete type[1]. There are some instances of code in
which the sizeof operator is being incorrectly/erroneously applied to
zero-length arrays and the result is zero. Such instances may be hiding
some bugs. So, this work (flexible-array member conversions) will also
help to get completely rid of those sorts of issues.
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 <[email protected]>
---
fs/squashfs/squashfs_fs.h | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/fs/squashfs/squashfs_fs.h b/fs/squashfs/squashfs_fs.h
index 7187bd1a30ea..8d64edb80ebf 100644
--- a/fs/squashfs/squashfs_fs.h
+++ b/fs/squashfs/squashfs_fs.h
@@ -262,7 +262,7 @@ struct squashfs_dir_index {
__le32 index;
__le32 start_block;
__le32 size;
- unsigned char name[0];
+ unsigned char name[];
};
struct squashfs_base_inode {
@@ -327,7 +327,7 @@ struct squashfs_symlink_inode {
__le32 inode_number;
__le32 nlink;
__le32 symlink_size;
- char symlink[0];
+ char symlink[];
};
struct squashfs_reg_inode {
@@ -341,7 +341,7 @@ struct squashfs_reg_inode {
__le32 fragment;
__le32 offset;
__le32 file_size;
- __le16 block_list[0];
+ __le16 block_list[];
};
struct squashfs_lreg_inode {
@@ -358,7 +358,7 @@ struct squashfs_lreg_inode {
__le32 fragment;
__le32 offset;
__le32 xattr;
- __le16 block_list[0];
+ __le16 block_list[];
};
struct squashfs_dir_inode {
@@ -389,7 +389,7 @@ struct squashfs_ldir_inode {
__le16 i_count;
__le16 offset;
__le32 xattr;
- struct squashfs_dir_index index[0];
+ struct squashfs_dir_index index[];
};
union squashfs_inode {
@@ -410,7 +410,7 @@ struct squashfs_dir_entry {
__le16 inode_number;
__le16 type;
__le16 size;
- char name[0];
+ char name[];
};
struct squashfs_dir_header {
@@ -428,12 +428,12 @@ struct squashfs_fragment_entry {
struct squashfs_xattr_entry {
__le16 type;
__le16 size;
- char data[0];
+ char data[];
};
struct squashfs_xattr_val {
__le32 vsize;
- char value[0];
+ char value[];
};
struct squashfs_xattr_id {
