linux-kernel - RE: [PATCH v2] acpica: fix -Wnull-pointer-arithmetic warnings

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Date:   Fri, 26 Jul 2019 19:35:49 +0000
From:   "Moore, Robert" <robert.moore@...el.com>
To:     Qian Cai <cai@....pw>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>
CC:     "Schmauss, Erik" <erik.schmauss@...el.com>,
        "jkim@...eBSD.org" <jkim@...eBSD.org>,
        "lenb@...nel.org" <lenb@...nel.org>,
        "ndesaulniers@...gle.com" <ndesaulniers@...gle.com>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "devel@...ica.org" <devel@...ica.org>,
        "clang-built-linux@...glegroups.com" 
        <clang-built-linux@...glegroups.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2] acpica: fix -Wnull-pointer-arithmetic warnings

We've taken the change to ACPI_TO_POINTER.
Thanks,
Bob


-----Original Message-----
From: Qian Cai [mailto:cai@....pw] 
Sent: Thursday, July 18, 2019 12:49 PM
To: Wysocki, Rafael J <rafael.j.wysocki@...el.com>
Cc: Moore, Robert <robert.moore@...el.com>; Schmauss, Erik <erik.schmauss@...el.com>; jkim@...eBSD.org; lenb@...nel.org; ndesaulniers@...gle.com; linux-acpi@...r.kernel.org; devel@...ica.org; clang-built-linux@...glegroups.com; linux-kernel@...r.kernel.org; Qian Cai <cai@....pw>
Subject: [PATCH v2] acpica: fix -Wnull-pointer-arithmetic warnings

Clang generate quite a few of those warnings.

drivers/acpi/scan.c:759:28: warning: arithmetic on a null pointer treated as a cast from integer to pointer is a GNU extension [-Wnull-pointer-arithmetic]
		status = acpi_get_handle(ACPI_ROOT_OBJECT,
obj->string.pointer,
                                         ^~~~~~~~~~~~~~~~
./include/acpi/actypes.h:458:56: note: expanded from macro 'ACPI_ROOT_OBJECT'
 #define ACPI_ROOT_OBJECT                ((acpi_handle) ACPI_TO_POINTER
(ACPI_MAX_PTR))
							^~~~~~~~~~~~~~~
./include/acpi/actypes.h:509:41: note: expanded from macro 'ACPI_TO_POINTER'
 #define ACPI_TO_POINTER(i)              ACPI_ADD_PTR (void, (void *) 0,
(acpi_size) (i))
                                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./include/acpi/actypes.h:503:84: note: expanded from macro 'ACPI_ADD_PTR'
 #define ACPI_ADD_PTR(t, a, b)           ACPI_CAST_PTR (t,
(ACPI_CAST_PTR (u8, (a)) + (acpi_size)(b)))
                                         ^~~~~~~~~~~~~~~~~
./include/acpi/actypes.h:501:66: note: expanded from macro 'ACPI_CAST_PTR'
 #define ACPI_CAST_PTR(t, p)             ((t *) (acpi_uintptr_t) (p))
                                                                 ^ This is because pointer arithmetic on a pointer not pointing to an array is an undefined behavior (C11 6.5.6, constraint 8). Fix it by just casting the corresponding pointers using ACPI_CAST_PTR() and skip the arithmetic. Also, fix a checkpatch warning together.

ERROR: Macros with complex values should be enclosed in parentheses
 #45: FILE: include/acpi/actypes.h:509:
+#define ACPI_TO_POINTER(i)              ACPI_CAST_PTR (void, i)

Signed-off-by: Qian Cai <cai@....pw>
---

v2: Use ACPI_CAST_PTR() in ACPI_TO_POINTER() directly without
    arithmetic.

 include/acpi/actypes.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/acpi/actypes.h b/include/acpi/actypes.h index ad6892a24015..163181e2d884 100644
--- a/include/acpi/actypes.h
+++ b/include/acpi/actypes.h
@@ -506,7 +506,7 @@ typedef u64 acpi_integer;
 
 /* Pointer/Integer type conversions */
 
-#define ACPI_TO_POINTER(i)              ACPI_ADD_PTR (void, (void *) 0, (acpi_size) (i))
+#define ACPI_TO_POINTER(i)              (ACPI_CAST_PTR (void, i))
 #define ACPI_TO_INTEGER(p)              ACPI_PTR_DIFF (p, (void *) 0)
 #define ACPI_OFFSET(d, f)               ACPI_PTR_DIFF (&(((d *) 0)->f), (void *) 0)
 #define ACPI_PHYSADDR_TO_PTR(i)         ACPI_TO_POINTER(i)
--
2.20.1 (Apple Git-117)