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Date: Sun, 17 Oct 2021 12:17:32 -0700 From: Randy Dunlap <rdunlap@...radead.org> To: Arnd Bergmann <arnd@...db.de> Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-arch <linux-arch@...r.kernel.org>, Geert Uytterhoeven <geert@...ux-m68k.org>, linux-m68k <linux-m68k@...ts.linux-m68k.org> Subject: Re: [PATCH] asm-generic: bug.h: add unreachable() in BUG() for CONFIG_BUG not set On 10/17/21 12:09 PM, Arnd Bergmann wrote: > On Sun, Oct 17, 2021 at 7:49 PM Randy Dunlap <rdunlap@...radead.org> wrote: >> >> When CONFIG_BUG is not set/enabled, there is a warning >> on ARCH=m68k, gcc version 11.1.0-nolibc from Arnd's crosstools: >> >> ../fs/afs/dir.c: In function 'afs_dir_set_page_dirty': >> ../fs/afs/dir.c:51:1: error: no return statement in function returning non-void [-Werror=return-type] >> >> Adding "unreachable()" in the BUG() macro silences the warning. > > No, I don't think this is the right solution: > >> -#define BUG() do {} while (1) >> +#define BUG() do {unreachable();} while (1) > > Marking this code unreachable() means the compiler is free > to assume any code path leading here will never be entered, > which leads to additional undefined behavior and other warnings > rather than just hanging reproducibly. > > The endless loop here should normally be sufficient to tell the > compiler that the function never returns, so it sounds like a > problem in gcc for m68k. Sounds likely. > Did you see any other issues like this one on m68k, or the > same one on another architecture? No and no. thanks. -- ~Randy
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