[PATCH v4 1/1] arch/sh: avoid spurious sizeof-pointer-div warning

[Michael Karcher]

Gcc warns about the pattern sizeof(void*)/sizeof(void), as it looks like
the abuse of a pattern to calculate the array size. This pattern appears
in the unevaluated part of the ternary operator in _INTC_ARRAY if the
parameter is NULL.

The replacement uses an alternate approach to return 0 in case of NULL
which does not generate the pattern sizeof(void*)/sizeof(void), but still
emits the warning if _INTC_ARRAY is called with a nonarray parameter.

This patch is required for successful compilation with -Werror enabled.

The idea to use _Generic for type distinction is taken from Comment #7
in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108483 by Jakub Jelinek

Signed-off-by: Michael Karcher <kernel@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>
---
This edition of the mail has the correct "v4" designation in the subject.

History:
v4:
  - Put the case distinction into the numerator instead of the denominator
  - Refactor the case disctinction into a second macro
v3:
  - I had a stern discussion with Thunderbird about not mangling the
    space characters in my email, and I hope spaces get sent as standard
    spaces now
v2:
  - improve title and remove mostly redundant first sentence of the
    description
  - adjust formatting of the _Generic construction

diff --git a/include/linux/sh_intc.h b/include/linux/sh_intc.h
index c255273b0281..98d1da0d8e36 100644
--- a/include/linux/sh_intc.h
+++ b/include/linux/sh_intc.h
@@ -97,7 +97,9 @@ struct intc_hw_desc {
     unsigned int nr_subgroups;
 };

-#define _INTC_ARRAY(a) a, __same_type(a, NULL) ? 0 : sizeof(a)/sizeof(*a)
+#define _INTC_SIZEOF_OR_ZERO(a) (_Generic(a,                 \
+                                 typeof(NULL):  0,           \
+                                 default:       sizeof(a)))
+#define _INTC_ARRAY(a) a, _INTC_SIZEOF_OR_ZERO(a)/sizeof(*a)

 #define INTC_HW_DESC(vectors, groups, mask_regs,    \
              prio_regs,    sense_regs, ack_regs)    \