From e8dc73c9f9ea554b36093dea23e4ca3b586105d7 Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Wed, 26 Feb 2020 15:26:12 -0600 Subject: xen: 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] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva Link: https://lore.kernel.org/r/20200226212612.GA4663@embeddedor Reviewed-by: Juergen Gross Signed-off-by: Boris Ostrovsky --- include/xen/interface/io/tpmif.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include') diff --git a/include/xen/interface/io/tpmif.h b/include/xen/interface/io/tpmif.h index 28e7dcd75e82..f8aa8bac5196 100644 --- a/include/xen/interface/io/tpmif.h +++ b/include/xen/interface/io/tpmif.h @@ -46,7 +46,7 @@ struct vtpm_shared_page { uint8_t pad; uint8_t nr_extra_pages; /* extra pages for long packets; may be zero */ - uint32_t extra_pages[0]; /* grant IDs; length in nr_extra_pages */ + uint32_t extra_pages[]; /* grant IDs; length in nr_extra_pages */ }; #endif -- cgit v1.2.3-59-g8ed1b