Messages in this thread | | | From | Nick Desaulniers <> | Date | Fri, 4 Mar 2022 11:26:47 -0800 | Subject | Re: [PATCH] x86/bug: __WARN_FLAGS: prevent shadowing by renaming local variable f to __flags |
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On Thu, Mar 3, 2022 at 3:08 AM Vincent Mailhol <mailhol.vincent@wanadoo.fr> wrote: > > The macro __WARN_FLAGS() uses a local variable named "f". This being a > common name, there is a risk of shadowing other variables. > > For example: > > | In file included from ./include/linux/bug.h:5, > | from ./include/linux/cpumask.h:14, > | from ./arch/x86/include/asm/cpumask.h:5, > | from ./arch/x86/include/asm/msr.h:11, > | from ./arch/x86/include/asm/processor.h:22, > | from ./arch/x86/include/asm/timex.h:5, > | from ./include/linux/timex.h:65, > | from ./include/linux/time32.h:13, > | from ./include/linux/time.h:60, > | from ./include/linux/stat.h:19, > | from ./include/linux/module.h:13, > | from virt/lib/irqbypass.mod.c:1: > | ./include/linux/rcupdate.h: In function 'rcu_head_after_call_rcu': > | ./arch/x86/include/asm/bug.h:80:21: warning: declaration of 'f' shadows a parameter [-Wshadow] > | 80 | __auto_type f = BUGFLAG_WARNING|(flags); \ > | | ^ > | ./include/asm-generic/bug.h:106:17: note: in expansion of macro '__WARN_FLAGS' > | 106 | __WARN_FLAGS(BUGFLAG_ONCE | \ > | | ^~~~~~~~~~~~ > | ./include/linux/rcupdate.h:1007:9: note: in expansion of macro 'WARN_ON_ONCE' > | 1007 | WARN_ON_ONCE(func != (rcu_callback_t)~0L); > | | ^~~~~~~~~~~~ > | In file included from ./include/linux/rbtree.h:24, > | from ./include/linux/mm_types.h:11, > | from ./include/linux/buildid.h:5, > | from ./include/linux/module.h:14, > | from virt/lib/irqbypass.mod.c:1: > | ./include/linux/rcupdate.h:1001:62: note: shadowed declaration is here > | 1001 | rcu_head_after_call_rcu(struct rcu_head *rhp, rcu_callback_t f) > | | ~~~~~~~~~~~~~~~^ > > This patch renames the variable from f to __flags (with two underscore > prefixes as suggested in the Linux kernel coding style [1]) in order > to prevent collisions. > > [1] Linux kernel coding style, section 12) Macros, Enums and RTL, > paragraph 5) namespace collisions when defining local variables in > macros resembling functions > https://www.kernel.org/doc/html/v4.10/process/coding-style.html#macros-enums-and-rtl
Ah, thanks for the patch. I missed that coding style recommendation. Might want to link to a newer (or evergreen) version of the docs though: https://www.kernel.org/doc/html/latest/process/coding-style.html#macros-enums-and-rtl Not sure what happens when we start shadowing variables named __flags, but maybe we cross that bridge if/when we get there.
Thanks for the fix! Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> -- Thanks, ~Nick Desaulniers
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