Skip to content

Commit 6e88abb

Browse files
uapi: linux: fiemap.h: Replace zero-length array with flexible-array member
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] KSPP#21 [3] commit 7649773 ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva <[email protected]>
1 parent d6cdad8 commit 6e88abb

File tree

1 file changed

+1
-1
lines changed

1 file changed

+1
-1
lines changed

include/uapi/linux/fiemap.h

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -34,7 +34,7 @@ struct fiemap {
3434
__u32 fm_mapped_extents;/* number of extents that were mapped (out) */
3535
__u32 fm_extent_count; /* size of fm_extents array (in) */
3636
__u32 fm_reserved;
37-
struct fiemap_extent fm_extents[0]; /* array of mapped extents (out) */
37+
struct fiemap_extent fm_extents[]; /* array of mapped extents (out) */
3838
};
3939

4040
#define FIEMAP_MAX_OFFSET (~0ULL)

0 commit comments

Comments
 (0)