Re: [linux-next:master 6345/7161] ipc/util.c:226:13: note: in expansion of macro 'max'

[Manfred Spraul <manfred@colorfullife.com>]

Hi,

Sorry - it seem that I forgot to retest the patch without sysctl() after 
converting from direct if/else to max().

On 4/12/19 8:43 PM, kbuild test robot wrote:
> [...]
>     ipc/util.c: In function 'ipc_idr_alloc':
>     include/linux/kernel.h:828:29: warning: comparison of distinct pointer types lacks a cast
>        (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
>                                  ^
>     include/linux/kernel.h:842:4: note: in expansion of macro '__typecheck'
>        (__typecheck(x, y) && __no_side_effects(x, y))
>         ^~~~~~~~~~~
>     include/linux/kernel.h:852:24: note: in expansion of macro '__safe_cmp'
>       __builtin_choose_expr(__safe_cmp(x, y), \
>                             ^~~~~~~~~~
>     include/linux/kernel.h:868:19: note: in expansion of macro '__careful_cmp'
>      #define max(x, y) __careful_cmp(x, y, >)
>                        ^~~~~~~~~~~~~
>>> ipc/util.c:226:13: note: in expansion of macro 'max'
>        max_idx = max(ids->in_use*3/2, ipc_min_cycle);
>                  ^~~
>
>     223		if (next_id < 0) { /* !CHECKPOINT_RESTORE or next_id is unset */
>     224			int max_idx;
>     225	
>   > 226			max_idx = max(ids->in_use*3/2, ipc_min_cycle);

With sysctl disabled, ipc_min_cycle is RADIX_TREE_MAP_SIZE, and this is

 > include/linux/radix-tree.h:#define RADIX_TREE_MAP_SIZE  (1UL << 
RADIX_TREE_MAP_SHIFT)

The checker behind max() is not smart enough to notice that 
RADIX_TREE_MAP_SIZE can be represented as int without an overflow.


What is the right approach?

 > #define ipc_min_cycle    ({    int tmp; tmp = RADIX_TREE_MAP_SIZE; tmp;})


--

     Manfred