From: Gustavo A. R. Silva Date: Mon, 20 Apr 2020 18:14:01 +0000 (-0500) Subject: m68k: amiga: config: Replace zero-length array with flexible-array member X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=366b8149fbff1965f9e25bb27dd4698d654be270;p=linux.git m68k: amiga: config: Replace zero-length array with flexible-array member 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 Link: https://lore.kernel.org/r/20200420181401.GA32172@embeddedor Signed-off-by: Geert Uytterhoeven --- diff --git a/arch/m68k/amiga/config.c b/arch/m68k/amiga/config.c index 777196e9c9bc4..4eb911d64e8da 100644 --- a/arch/m68k/amiga/config.c +++ b/arch/m68k/amiga/config.c @@ -629,7 +629,7 @@ struct savekmsg { unsigned long magic2; /* SAVEKMSG_MAGIC2 */ unsigned long magicptr; /* address of magic1 */ unsigned long size; - char data[0]; + char data[]; }; static struct savekmsg *savekmsg;