Message-ID: <563ff850-9966-b790-96d4-bb0557e1152c@mkarcher.dialup.fu-berlin.de>
Date:   Sun, 22 Jan 2023 17:27:11 +0100
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To:     linux-kernel@vger.kernel.org, linux-sh@vger.kernel.org,
        Segher Boessenkool <segher@kernel.crashing.org>,
        Rich Felker <dalias@libc.org>,
        Yoshinori Sato <ysato@users.sourceforge.jp>,
        John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
From:   Michael Karcher <kernel@mkarcher.dialup.fu-berlin.de>
Subject: [PATCH v2 1/1] arch/sh: avoid spurious sizeof-pointer-div warning
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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@mkarcher.dialup.fu-berlin.de>
---
History:
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_ARRAY(a) a, sizeof(a) / (_Generic(a, \
+                                       typeof(NULL):  (size_t)-1, \
+                                       default:       sizeof(*a)))

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