Pull flexible-array member conversion from Gustavo Silva: "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 convertions) will also help to get completely rid of those sorts of issues. Notice that all of these patches have been baking in linux-next for quite a while now and, 238 more of these patches have already been merged into 5.7-rc1. There are a couple hundred more of these issues waiting to be addressed in the whole codebase" [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") * tag 'flexible-array-member-5.7-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux: (28 commits) xattr.h: Replace zero-length array with flexible-array member uapi: linux: fiemap.h: Replace zero-length array with flexible-array member uapi: linux: dlm_device.h: Replace zero-length array with flexible-array member tpm_eventlog.h: Replace zero-length array with flexible-array member ti_wilink_st.h: Replace zero-length array with flexible-array member swap.h: Replace zero-length array with flexible-array member skbuff.h: Replace zero-length array with flexible-array member sched: topology.h: Replace zero-length array with flexible-array member rslib.h: Replace zero-length array with flexible-array member rio.h: Replace zero-length array with flexible-array member posix_acl.h: Replace zero-length array with flexible-array member platform_data: wilco-ec.h: Replace zero-length array with flexible-array member memcontrol.h: Replace zero-length array with flexible-array member list_lru.h: Replace zero-length array with flexible-array member lib: cpu_rmap: Replace zero-length array with flexible-array member irq.h: Replace zero-length array with flexible-array member ihex.h: Replace zero-length array with flexible-array member igmp.h: Replace zero-length array with flexible-array member genalloc.h: Replace zero-length array with flexible-array member ethtool.h: Replace zero-length array with flexible-array member ...
Showing the changes to include/uapi/linux (2 of 28 files). Show all
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| @@ -45,13 +45,13 @@ struct dlm_lock_params { · 44 unmodified lines | |||
| 45 | void __user *bastaddr; | 45 | void __user *bastaddr; |
| 46 | struct dlm_lksb __user *lksb; | 46 | struct dlm_lksb __user *lksb; |
| 47 | char lvb[DLM_USER_LVB_LEN]; | 47 | char lvb[DLM_USER_LVB_LEN]; |
| 48 | char name[0]; | 48 | char name[]; |
| 49 | }; | 49 | }; |
| 50 | 50 | ||
| 51 | struct dlm_lspace_params { | 51 | struct dlm_lspace_params { |
| 52 | __u32 flags; | 52 | __u32 flags; |
| 53 | __u32 minor; | 53 | __u32 minor; |
| 54 | char name[0]; | 54 | char name[]; |
| 55 | }; | 55 | }; |
| 56 | 56 | ||
| 57 | struct dlm_purge_params { | 57 | struct dlm_purge_params { |
| @@ -34,7 +34,7 @@ struct fiemap { · 33 unmodified lines | |||
| 34 | __u32 fm_mapped_extents;/* number of extents that were mapped (out) */ | 34 | __u32 fm_mapped_extents;/* number of extents that were mapped (out) */ |
| 35 | __u32 fm_extent_count; /* size of fm_extents array (in) */ | 35 | __u32 fm_extent_count; /* size of fm_extents array (in) */ |
| 36 | __u32 fm_reserved; | 36 | __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) */ |
| 38 | }; | 38 | }; |
| 39 | 39 | ||
| 40 | #define FIEMAP_MAX_OFFSET (~0ULL) | 40 | #define FIEMAP_MAX_OFFSET (~0ULL) |