From: "Gustavo A. R. Silva" <gustavo@embeddedor.com> To: "Vitor Soares" <vitor.soares@synopsys.com>, "Boris Brezillon" <bbrezillon@kernel.org>, "Przemysław Gaj" <pgaj@cadence.com> Cc: linux-i3c@lists.infradead.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" <gustavo@embeddedor.com> Subject: [PATCH] i3c: master: Replace zero-length array with flexible-array member Date: Thu, 27 Feb 2020 07:13:07 -0600 [thread overview] Message-ID: <20200227131307.GA24935@embeddedor> (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. [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> --- drivers/i3c/master/dw-i3c-master.c | 2 +- drivers/i3c/master/i3c-master-cdns.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/i3c/master/dw-i3c-master.c b/drivers/i3c/master/dw-i3c-master.c index bd26c3b9634e..5c5306cd50ec 100644 --- a/drivers/i3c/master/dw-i3c-master.c +++ b/drivers/i3c/master/dw-i3c-master.c @@ -221,7 +221,7 @@ struct dw_i3c_xfer { struct completion comp; int ret; unsigned int ncmds; - struct dw_i3c_cmd cmds[0]; + struct dw_i3c_cmd cmds[]; }; struct dw_i3c_master { diff --git a/drivers/i3c/master/i3c-master-cdns.c b/drivers/i3c/master/i3c-master-cdns.c index 54712793709e..3fee8bd7fe20 100644 --- a/drivers/i3c/master/i3c-master-cdns.c +++ b/drivers/i3c/master/i3c-master-cdns.c @@ -388,7 +388,7 @@ struct cdns_i3c_xfer { struct completion comp; int ret; unsigned int ncmds; - struct cdns_i3c_cmd cmds[0]; + struct cdns_i3c_cmd cmds[]; }; struct cdns_i3c_data { -- 2.25.0
WARNING: multiple messages have this Message-ID (diff)
From: "Gustavo A. R. Silva" <gustavo@embeddedor.com> To: "Vitor Soares" <vitor.soares@synopsys.com>, "Boris Brezillon" <bbrezillon@kernel.org>, "Przemysław Gaj" <pgaj@cadence.com> Cc: linux-i3c@lists.infradead.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" <gustavo@embeddedor.com> Subject: [PATCH] i3c: master: Replace zero-length array with flexible-array member Date: Thu, 27 Feb 2020 07:13:07 -0600 [thread overview] Message-ID: <20200227131307.GA24935@embeddedor> (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. [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> --- drivers/i3c/master/dw-i3c-master.c | 2 +- drivers/i3c/master/i3c-master-cdns.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/i3c/master/dw-i3c-master.c b/drivers/i3c/master/dw-i3c-master.c index bd26c3b9634e..5c5306cd50ec 100644 --- a/drivers/i3c/master/dw-i3c-master.c +++ b/drivers/i3c/master/dw-i3c-master.c @@ -221,7 +221,7 @@ struct dw_i3c_xfer { struct completion comp; int ret; unsigned int ncmds; - struct dw_i3c_cmd cmds[0]; + struct dw_i3c_cmd cmds[]; }; struct dw_i3c_master { diff --git a/drivers/i3c/master/i3c-master-cdns.c b/drivers/i3c/master/i3c-master-cdns.c index 54712793709e..3fee8bd7fe20 100644 --- a/drivers/i3c/master/i3c-master-cdns.c +++ b/drivers/i3c/master/i3c-master-cdns.c @@ -388,7 +388,7 @@ struct cdns_i3c_xfer { struct completion comp; int ret; unsigned int ncmds; - struct cdns_i3c_cmd cmds[0]; + struct cdns_i3c_cmd cmds[]; }; struct cdns_i3c_data { -- 2.25.0 _______________________________________________ linux-i3c mailing list linux-i3c@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-i3c
next reply other threads:[~2020-02-27 13:10 UTC|newest] Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-02-27 13:13 Gustavo A. R. Silva [this message] 2020-02-27 13:13 ` [PATCH] i3c: master: Replace zero-length array with flexible-array member Gustavo A. R. Silva
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