Messages in this thread Patch in this message | | | Date | Mon, 9 Mar 2020 15:23:27 -0500 | From | "Gustavo A. R. Silva" <> | Subject | [PATCH][next] pstore: ram_core: Replace zero-length array with flexible-array member |
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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: Gustavo A. R. Silva <gustavo@embeddedor.com> --- fs/pstore/ram_core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c index 1f4d8c06f9be..c917c191e78c 100644 --- a/fs/pstore/ram_core.c +++ b/fs/pstore/ram_core.c @@ -34,7 +34,7 @@ struct persistent_ram_buffer { uint32_t sig; atomic_t start; atomic_t size; - uint8_t data[0]; + uint8_t data[]; }; #define PERSISTENT_RAM_SIG (0x43474244) /* DBGC */ -- 2.25.0
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