From 9b5816b56af6a424619ab51d24de34dfc65102d8 Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Thu, 7 May 2020 13:53:13 -0500 Subject: gnss: replace zero-length array with flexible-array 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] sizeof(flexible-array-member) triggers a warning because flexible array members have incomplete type[1]. There are some instances of code in which the sizeof operator is being incorrectly/erroneously applied to zero-length arrays and the result is zero. Such instances may be hiding some bugs. So, this work (flexible-array member conversions) will also help to get completely rid of those sorts of issues. 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 Signed-off-by: Johan Hovold --- drivers/gnss/serial.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/gnss') diff --git a/drivers/gnss/serial.h b/drivers/gnss/serial.h index 980ffdc86c2a..621953f7821d 100644 --- a/drivers/gnss/serial.h +++ b/drivers/gnss/serial.h @@ -16,7 +16,7 @@ struct gnss_serial { struct gnss_device *gdev; speed_t speed; const struct gnss_serial_ops *ops; - unsigned long drvdata[0]; + unsigned long drvdata[]; }; enum gnss_serial_pm_state { -- cgit v1.2.3