| Message ID | 1586599916-15456-1-git-send-email-qiwuchen55@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [RESEND,1/3] mm: Replace zero-length array with flexible-array member | expand |
On Sat, Apr 11, 2020 at 06:11:54PM +0800, qiwuchen55@gmail.com wrote: >From: chenqiwu <chenqiwu@xiaomi.com> > >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] https://github.com/KSPP/linux/issues/21 >[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") > >Signed-off-by: chenqiwu <chenqiwu@xiaomi.com> The change looks good to me. Reviewed-by: Wei Yang <richard.weiyang@gmail.com> >--- > include/linux/mm.h | 2 +- > include/linux/mmzone.h | 2 +- > include/linux/swap.h | 2 +- > 3 files changed, 3 insertions(+), 3 deletions(-) > >diff --git a/include/linux/mm.h b/include/linux/mm.h >index 5a32342..9831bb5 100644 >--- a/include/linux/mm.h >+++ b/include/linux/mm.h >@@ -1718,7 +1718,7 @@ struct frame_vector { > unsigned int nr_frames; /* Number of frames stored in ptrs array */ > bool got_ref; /* Did we pin pages by getting page ref? */ > bool is_pfns; /* Does array contain pages or pfns? */ >- void *ptrs[0]; /* Array of pinned pfns / pages. Use >+ void *ptrs[]; /* Array of pinned pfns / pages. Use > * pfns_vector_pages() or pfns_vector_pfns() > * for access */ > }; >diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h >index 1b9de7d..f6b9fa9 100644 >--- a/include/linux/mmzone.h >+++ b/include/linux/mmzone.h >@@ -1147,7 +1147,7 @@ struct mem_section_usage { > DECLARE_BITMAP(subsection_map, SUBSECTIONS_PER_SECTION); > #endif > /* See declaration of similar field in struct zone */ >- unsigned long pageblock_flags[0]; >+ unsigned long pageblock_flags[]; > }; > > void subsection_map_init(unsigned long pfn, unsigned long nr_pages); >diff --git a/include/linux/swap.h b/include/linux/swap.h >index b835d8d..e1bbf7a 100644 >--- a/include/linux/swap.h >+++ b/include/linux/swap.h >@@ -275,7 +275,7 @@ struct swap_info_struct { > */ > struct work_struct discard_work; /* discard worker */ > struct swap_cluster_list discard_clusters; /* discard clusters list */ >- struct plist_node avail_lists[0]; /* >+ struct plist_node avail_lists[]; /* > * entries in swap_avail_heads, one > * entry per node. > * Must be last as the number of the >-- >1.9.1
diff --git a/include/linux/mm.h b/include/linux/mm.h index 5a32342..9831bb5 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1718,7 +1718,7 @@ struct frame_vector { unsigned int nr_frames; /* Number of frames stored in ptrs array */ bool got_ref; /* Did we pin pages by getting page ref? */ bool is_pfns; /* Does array contain pages or pfns? */ - void *ptrs[0]; /* Array of pinned pfns / pages. Use + void *ptrs[]; /* Array of pinned pfns / pages. Use * pfns_vector_pages() or pfns_vector_pfns() * for access */ }; diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 1b9de7d..f6b9fa9 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -1147,7 +1147,7 @@ struct mem_section_usage { DECLARE_BITMAP(subsection_map, SUBSECTIONS_PER_SECTION); #endif /* See declaration of similar field in struct zone */ - unsigned long pageblock_flags[0]; + unsigned long pageblock_flags[]; }; void subsection_map_init(unsigned long pfn, unsigned long nr_pages); diff --git a/include/linux/swap.h b/include/linux/swap.h index b835d8d..e1bbf7a 100644 --- a/include/linux/swap.h +++ b/include/linux/swap.h @@ -275,7 +275,7 @@ struct swap_info_struct { */ struct work_struct discard_work; /* discard worker */ struct swap_cluster_list discard_clusters; /* discard clusters list */ - struct plist_node avail_lists[0]; /* + struct plist_node avail_lists[]; /* * entries in swap_avail_heads, one * entry per node. * Must be last as the number of the