• Gustavo A. R. Silva's avatar
    leds: leds-pwm: Replace zero-length array with flexible-array member · 7bbec6c4
    Gustavo A. R. Silva authored
    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 76497732 ("cxgb3/l2t: Fix undefined behaviour")
    Signed-off-by: default avatarGustavo A. R. Silva <gustavo@embeddedor.com>
    Signed-off-by: default avatarPavel Machek <pavel@ucw.cz>
    7bbec6c4
leds-pwm.c 4.45 KB