Linux-HyperV Archive on
 help / color / Atom feed
From: "Gustavo A. R. Silva" <>
To: "K. Y. Srinivasan" <>,
	Haiyang Zhang <>,
	Stephen Hemminger <>,
	Sasha Levin <>,
	Lorenzo Pieralisi <>,
	Andrew Murray <>,
	Bjorn Helgaas <>
	"Gustavo A. R. Silva" <>
Subject: [PATCH] PCI: hv: Replace zero-length array with flexible-array member
Date: Wed, 12 Feb 2020 18:50:48 -0600
Message-ID: <> (raw)

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.

[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <>
 drivers/pci/controller/pci-hyperv.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index 9977abff92fc..be957268f9d6 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -260,7 +260,7 @@ struct pci_packet {
 				int resp_packet_size);
 	void *compl_ctxt;
-	struct pci_message message[0];
+	struct pci_message message[];
@@ -296,7 +296,7 @@ struct pci_bus_d0_entry {
 struct pci_bus_relations {
 	struct pci_incoming_message incoming;
 	u32 device_count;
-	struct pci_function_description func[0];
+	struct pci_function_description func[];
 } __packed;
 struct pci_q_res_req_response {
@@ -508,7 +508,7 @@ struct hv_dr_work {
 struct hv_dr_state {
 	struct list_head list_entry;
 	u32 device_count;
-	struct pci_function_description func[0];
+	struct pci_function_description func[];
 enum hv_pcichild_state {

             reply index

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-13  0:50 Gustavo A. R. Silva [this message]
2020-02-13  3:43 ` Dexuan Cui

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \ \ \ \ \ \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-HyperV Archive on

Archives are clonable:
	git clone --mirror linux-hyperv/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-hyperv linux-hyperv/ \
	public-inbox-index linux-hyperv

Example config snippet for mirrors

Newsgroup available over NNTP:

AGPL code for this site: git clone