On Fri, Mar 19, 2021 at 10:24:43PM -0400, Alan Stern wrote: > On Sat, Mar 20, 2021 at 09:31:51AM +0800, Jay Fang wrote: > > From: Zihao Tang <tangzihao1@xxxxxxxxxxxxx> > > > > Fix the following smatch warnings: > > > > drivers/usb/host/ohci-hcd.c:1318 ohci_hcd_mod_init() warn: > > ignoring unreachable code. > > > > platform_driver_register(&TMIO_OHCI_DRIVER) is the last > > platform_driver_register() call in ohci_hcd_mod_init(), so if it > > failed, there's no need to unregister it, but just goto error_tmio. > > > > So remove the unreachable platform_driver_unregister(&TMIO_OHCI_DRIVER). > > No functionality change. > > Doesn't the compiler realize that the call is unreachable, and > therefore avoid generating any object for it? > This is a static checker warning. For example, Heart Bleed bug was an ignored unreachable code static checker warning. > It's true that the function call is, strictly speaking, unnecessary. > However, it provides a pleasing symmetry and it acts as a guide in the > unlikely event that anyone wants to add another platform-specific > driver in the future. Hopefully future programmers can figure out basic stuff like that. This code doesn't trigger a Smatch warning on my .config because the Smatch check doesn't warn if the previous line was an #endif. On the other hand, the ifdefs are also why I forwarded the email when I saw the warning from kbuild. Normally kbuild is better at picking the person to blame but because this is a .config thing that confused it. Anyway, I glanced at the warning and thought it looked suspicious enough to warrant a further look. When I first wrote the Smatch unreachable code warning there were a handful of places which used that style of code: return 0; unreachable_release(); err_release: release_something(); I just left those as-is because it was obvious to me that it was done intentionally. However, it seems that other people have removed all of those behind my back so I can't find an example of this now except for in ohci_hcd_mod_init(). Anyway, I would have put a special case to silence these false positives but it wasn't common practice in 2014 and no one does it these days. regards, dan carpenter
