Re: [Xen-devel] [PATCH 2/8] xen/misc: Remove or annotate possibly-unused functions

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 09.02.16 at 21:01, <andrew.cooper3@xxxxxxxxxx> wrote:
> --- a/xen/common/rcupdate.c
> +++ b/xen/common/rcupdate.c
> @@ -141,12 +141,6 @@ static inline int rcu_batch_before(long a, long b)
>      return (a - b) < 0;
>  }
>  
> -/* Is batch a after batch b ? */
> -static inline int rcu_batch_after(long a, long b)
> -{
> -    return (a - b) > 0;
> -}

To me it is the nature of inline functions that they may or may not be
used, regardless of whether they live in a header file (where I would
have supposed Clang won't warn about, but the change below makes
me assume I'm wrong) or in a source file.

> --- a/xen/include/xen/compat.h
> +++ b/xen/include/xen/compat.h
> @@ -134,14 +134,16 @@
>  #define CHECK_NAME_(k, n, tag) __check ## tag ## k ## _ ## n
>  
>  #define CHECK_TYPE(name) \
> -static inline int CHECK_NAME(name, T)(xen_ ## name ## _t *x, \
> -                                      compat_ ## name ## _t *c) \
> +static inline int __maybe_unused \
> +CHECK_NAME(name, T)(xen_ ## name ## _t *x, \
> +                    compat_ ## name ## _t *c) \
>  { \
>      return x == c; \
>  }
>  #define CHECK_TYPE_(k, n) \
> -static inline int CHECK_NAME_(k, n, T)(k xen_ ## n *x, \
> -                                       k compat_ ## n *c) \
> +static inline int __maybe_unused \
> +CHECK_NAME_(k, n, T)(k xen_ ## n *x, \
> +                     k compat_ ## n *c) \
>  { \
>      return x == c; \
>  }
> @@ -154,14 +156,14 @@ static inline int CHECK_NAME_(k, n, T)(k xen_ ## n *x, \
>                                            sizeof(k compat_ ## n)) * 2]
>  
>  #define CHECK_FIELD_COMMON(name, t, f) \
> -static inline int name(xen_ ## t ## _t *x, compat_ ## t ## _t *c) \
> +static inline int __maybe_unused name(xen_ ## t ## _t *x, compat_ ## t ## _t 
> *c) \
>  { \
>      BUILD_BUG_ON(offsetof(xen_ ## t ## _t, f) != \
>                   offsetof(compat_ ## t ## _t, f)); \
>      return &x->f == &c->f; \
>  }
>  #define CHECK_FIELD_COMMON_(k, name, n, f) \
> -static inline int name(k xen_ ## n *x, k compat_ ## n *c) \
> +static inline int __maybe_unused name(k xen_ ## n *x, k compat_ ## n *c) \
>  { \
>      BUILD_BUG_ON(offsetof(k xen_ ## n, f) != \
>                   offsetof(k compat_ ## n, f)); \

So if these are all noticed to be unused, why would others in other
header files not be? I think there's at the very least some aspect
missing in the description, explaining what makes these stand out
from the others.

Jan


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