On 11/04/24 10:04, Arnd Bergmann wrote: > On Wed, Apr 10, 2024, at 17:32, Adrian Hunter wrote: >> BUG() does not return, and arch implementations of BUG() use unreachable() >> or other non-returning code. However with !CONFIG_BUG, the default >> implementation is often used instead, and that does not do that. x86 always >> uses its own implementation, but powerpc with !CONFIG_BUG gives a build >> error: >> >> kernel/time/timekeeping.c: In function ‘timekeeping_debug_get_ns’: >> kernel/time/timekeeping.c:286:1: error: no return statement in function >> returning non-void [-Werror=return-type] >> >> Add unreachable() to default !CONFIG_BUG BUG() implementation. > > I'm a bit worried about this patch, since we have had problems > with unreachable() inside of BUG() in the past, and as far as I > can remember, the current version was the only one that > actually did the right thing on all compilers. > > One problem with an unreachable() annotation here is that if > a compiler misanalyses the endless loop, it can decide to > throw out the entire code path leading up to it and just > run into undefined behavior instead of printing a BUG() > message. > > Do you know which compiler version show the warning above? Original report has a list https://lore.kernel.org/all/CA+G9fYvjdZCW=7ZGxS6A_3bysjQ56YF7S-+PNLQ_8a4DKh1Bhg@xxxxxxxxxxxxxx/
