From 880a7817c1a82a93d3f83dfb25dce1f0db629c66 Mon Sep 17 00:00:00 2001 From: Philippe Mathieu-Daudé Date: Wed, 4 Mar 2020 16:38:16 +0100 Subject: misc: Replace zero-length arrays with flexible array member (manual) Description copied from Linux kernel commit from Gustavo A. R. Silva (see [3]): --v-- description start --v-- 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], 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 unadvertenly introduced [2] to the Linux codebase from now on. --^-- description end --^-- Do the similar housekeeping in the QEMU codebase (which uses C99 since commit 7be41675f7cb). All these instances of code were found with the help of the following command (then manual analysis, without modifying structures only having a single flexible array member, such QEDTable in block/qed.h): git grep -F '[0];' [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=76497732932f [3] https://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux.git/commit/?id=17642a2fbd2c1 Inspired-by: Gustavo A. R. Silva Reviewed-by: David Hildenbrand Signed-off-by: Philippe Mathieu-Daudé Signed-off-by: Paolo Bonzini --- docs/interop/vhost-user.rst | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'docs/interop') diff --git a/docs/interop/vhost-user.rst b/docs/interop/vhost-user.rst index 401652397c..3b1b6602c7 100644 --- a/docs/interop/vhost-user.rst +++ b/docs/interop/vhost-user.rst @@ -568,7 +568,7 @@ For split virtqueue, queue region can be implemented as: uint16_t used_idx; /* Used to track the state of each descriptor in descriptor table */ - DescStateSplit desc[0]; + DescStateSplit desc[]; } QueueRegionSplit; To track inflight I/O, the queue region should be processed as follows: @@ -690,7 +690,7 @@ For packed virtqueue, queue region can be implemented as: uint8_t padding[7]; /* Used to track the state of each descriptor fetched from descriptor ring */ - DescStatePacked desc[0]; + DescStatePacked desc[]; } QueueRegionPacked; To track inflight I/O, the queue region should be processed as follows: -- cgit v1.2.3-55-g7522