* [Qemu-devel] [PATCH for 2.7] atomic: strip "const" from variables declared with typeof
@ 2016-08-08 12:19 Paolo Bonzini
2016-08-08 12:23 ` no-reply
0 siblings, 1 reply; 2+ messages in thread
From: Paolo Bonzini @ 2016-08-08 12:19 UTC (permalink / raw)
To: qemu-devel; +Cc: bobby.prani, rth
With the latest clang, we have the following warning:
/home/pranith/devops/code/qemu/include/qemu/seqlock.h:62:21: warning: passing 'typeof (*&sl->sequence) *' (aka 'const unsigned int *') to parameter of type 'unsigned int *' discards qualifiers [-Wincompatible-pointer-types-discards-qualifiers]
return unlikely(atomic_read(&sl->sequence) != start);
^~~~~~~~~~~~~~~~~~~~~~~~~~
/home/pranith/devops/code/qemu/include/qemu/atomic.h:58:25: note: expanded from macro 'atomic_read'
__atomic_load(ptr, &_val, __ATOMIC_RELAXED); \
^~~~~
Stripping const is a bit tricky due to promotions, but it is doable
with either C11 _Generic or GCC extensions. Use the latter.
Reported-by: Pranith Kumar <bobby.prani@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
include/qemu/atomic.h | 48 ++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 42 insertions(+), 6 deletions(-)
diff --git a/include/qemu/atomic.h b/include/qemu/atomic.h
index 7e13fca..fc9cfa2 100644
--- a/include/qemu/atomic.h
+++ b/include/qemu/atomic.h
@@ -18,6 +18,42 @@
/* Compiler barrier */
#define barrier() ({ asm volatile("" ::: "memory"); (void)0; })
+/* The variable that receives the old value of an atomically-accessed
+ * variable must be non-qualified, because atomic builtins return values
+ * through a pointer-type argument as in __atomic_load(&var, &old, MODEL).
+ *
+ * This macro has to handle types smaller than int manually, because of
+ * implicit promotion. int and larger types, as well as pointers, can be
+ * converted to a non-qualified type just by applying a binary operator.
+ */
+#define typeof_strip_qual(expr) \
+ typeof( \
+ __builtin_choose_expr( \
+ __builtin_types_compatible_p(typeof(expr), signed char) || \
+ __builtin_types_compatible_p(typeof(expr), const signed char) || \
+ __builtin_types_compatible_p(typeof(expr), volatile signed char) || \
+ __builtin_types_compatible_p(typeof(expr), const volatile signed char), \
+ (signed char)1, \
+ __builtin_choose_expr( \
+ __builtin_types_compatible_p(typeof(expr), unsigned char) || \
+ __builtin_types_compatible_p(typeof(expr), const unsigned char) || \
+ __builtin_types_compatible_p(typeof(expr), volatile unsigned char) || \
+ __builtin_types_compatible_p(typeof(expr), const volatile unsigned char), \
+ (unsigned char)1, \
+ __builtin_choose_expr( \
+ __builtin_types_compatible_p(typeof(expr), signed short) || \
+ __builtin_types_compatible_p(typeof(expr), const signed short) || \
+ __builtin_types_compatible_p(typeof(expr), volatile signed short) || \
+ __builtin_types_compatible_p(typeof(expr), const volatile signed short), \
+ (signed short)1, \
+ __builtin_choose_expr( \
+ __builtin_types_compatible_p(typeof(expr), unsigned short) || \
+ __builtin_types_compatible_p(typeof(expr), const unsigned short) || \
+ __builtin_types_compatible_p(typeof(expr), volatile unsigned short) || \
+ __builtin_types_compatible_p(typeof(expr), const volatile unsigned short), \
+ (unsigned short)1, \
+ (expr)+0)))))
+
#ifdef __ATOMIC_RELAXED
/* For C11 atomic ops */
@@ -54,7 +90,7 @@
#define atomic_read(ptr) \
({ \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
- typeof(*ptr) _val; \
+ typeof_strip_qual(*ptr) _val; \
__atomic_load(ptr, &_val, __ATOMIC_RELAXED); \
_val; \
})
@@ -80,7 +116,7 @@
#define atomic_rcu_read(ptr) \
({ \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
- typeof(*ptr) _val; \
+ typeof_strip_qual(*ptr) _val; \
atomic_rcu_read__nocheck(ptr, &_val); \
_val; \
})
@@ -103,7 +139,7 @@
#define atomic_mb_read(ptr) \
({ \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
- typeof(*ptr) _val; \
+ typeof_strip_qual(*ptr) _val; \
__atomic_load(ptr, &_val, __ATOMIC_RELAXED); \
smp_rmb(); \
_val; \
@@ -120,7 +156,7 @@
#define atomic_mb_read(ptr) \
({ \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
- typeof(*ptr) _val; \
+ typeof_strip_qual(*ptr) _val; \
__atomic_load(ptr, &_val, __ATOMIC_SEQ_CST); \
_val; \
})
@@ -137,7 +173,7 @@
#define atomic_xchg(ptr, i) ({ \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
- typeof(*ptr) _new = (i), _old; \
+ typeof_strip_qual(*ptr) _new = (i), _old; \
__atomic_exchange(ptr, &_new, &_old, __ATOMIC_SEQ_CST); \
_old; \
})
@@ -146,7 +182,7 @@
#define atomic_cmpxchg(ptr, old, new) \
({ \
QEMU_BUILD_BUG_ON(sizeof(*ptr) > sizeof(void *)); \
- typeof(*ptr) _old = (old), _new = (new); \
+ typeof_strip_qual(*ptr) _old = (old), _new = (new); \
__atomic_compare_exchange(ptr, &_old, &_new, false, \
__ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST); \
_old; \
--
2.7.4
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [Qemu-devel] [PATCH for 2.7] atomic: strip "const" from variables declared with typeof
2016-08-08 12:19 [Qemu-devel] [PATCH for 2.7] atomic: strip "const" from variables declared with typeof Paolo Bonzini
@ 2016-08-08 12:23 ` no-reply
0 siblings, 0 replies; 2+ messages in thread
From: no-reply @ 2016-08-08 12:23 UTC (permalink / raw)
To: pbonzini; +Cc: famz, qemu-devel, bobby.prani, rth
Hi,
Your series seems to have some coding style problems. See output below for
more information:
Message-id: 1470658774-16049-1-git-send-email-pbonzini@redhat.com
Type: series
Subject: [Qemu-devel] [PATCH for 2.7] atomic: strip "const" from variables declared with typeof
=== TEST SCRIPT BEGIN ===
#!/bin/bash
BASE=base
n=1
total=$(git log --oneline $BASE.. | wc -l)
failed=0
commits="$(git log --format=%H --reverse $BASE..)"
for c in $commits; do
echo "Checking PATCH $n/$total: $(git show --no-patch --format=%s $c)..."
if ! git show $c --format=email | ./scripts/checkpatch.pl --mailback -; then
failed=1
echo
fi
n=$((n+1))
done
exit $failed
=== TEST SCRIPT END ===
Updating 3c8cf5a9c21ff8782164d1def7f44bd888713384
From https://github.com/patchew-project/qemu
* [new tag] patchew/1470658774-16049-1-git-send-email-pbonzini@redhat.com -> patchew/1470658774-16049-1-git-send-email-pbonzini@redhat.com
Switched to a new branch 'test'
5cd912b atomic: strip "const" from variables declared with typeof
=== OUTPUT BEGIN ===
Checking PATCH 1/1: atomic: strip "const" from variables declared with typeof...
WARNING: line over 80 characters
#38: FILE: include/qemu/atomic.h:29:
+#define typeof_strip_qual(expr) \
WARNING: line over 80 characters
#39: FILE: include/qemu/atomic.h:30:
+ typeof( \
WARNING: line over 80 characters
#40: FILE: include/qemu/atomic.h:31:
+ __builtin_choose_expr( \
WARNING: line over 80 characters
#41: FILE: include/qemu/atomic.h:32:
+ __builtin_types_compatible_p(typeof(expr), signed char) || \
WARNING: line over 80 characters
#42: FILE: include/qemu/atomic.h:33:
+ __builtin_types_compatible_p(typeof(expr), const signed char) || \
WARNING: line over 80 characters
#43: FILE: include/qemu/atomic.h:34:
+ __builtin_types_compatible_p(typeof(expr), volatile signed char) || \
WARNING: Use of volatile is usually wrong: see Documentation/volatile-considered-harmful.txt
#43: FILE: include/qemu/atomic.h:34:
+ __builtin_types_compatible_p(typeof(expr), volatile signed char) || \
WARNING: line over 80 characters
#44: FILE: include/qemu/atomic.h:35:
+ __builtin_types_compatible_p(typeof(expr), const volatile signed char), \
WARNING: Use of volatile is usually wrong: see Documentation/volatile-considered-harmful.txt
#44: FILE: include/qemu/atomic.h:35:
+ __builtin_types_compatible_p(typeof(expr), const volatile signed char), \
WARNING: line over 80 characters
#45: FILE: include/qemu/atomic.h:36:
+ (signed char)1, \
WARNING: line over 80 characters
#46: FILE: include/qemu/atomic.h:37:
+ __builtin_choose_expr( \
WARNING: line over 80 characters
#47: FILE: include/qemu/atomic.h:38:
+ __builtin_types_compatible_p(typeof(expr), unsigned char) || \
WARNING: line over 80 characters
#48: FILE: include/qemu/atomic.h:39:
+ __builtin_types_compatible_p(typeof(expr), const unsigned char) || \
WARNING: line over 80 characters
#49: FILE: include/qemu/atomic.h:40:
+ __builtin_types_compatible_p(typeof(expr), volatile unsigned char) || \
WARNING: Use of volatile is usually wrong: see Documentation/volatile-considered-harmful.txt
#49: FILE: include/qemu/atomic.h:40:
+ __builtin_types_compatible_p(typeof(expr), volatile unsigned char) || \
WARNING: line over 80 characters
#50: FILE: include/qemu/atomic.h:41:
+ __builtin_types_compatible_p(typeof(expr), const volatile unsigned char), \
WARNING: Use of volatile is usually wrong: see Documentation/volatile-considered-harmful.txt
#50: FILE: include/qemu/atomic.h:41:
+ __builtin_types_compatible_p(typeof(expr), const volatile unsigned char), \
WARNING: line over 80 characters
#51: FILE: include/qemu/atomic.h:42:
+ (unsigned char)1, \
WARNING: line over 80 characters
#52: FILE: include/qemu/atomic.h:43:
+ __builtin_choose_expr( \
WARNING: line over 80 characters
#53: FILE: include/qemu/atomic.h:44:
+ __builtin_types_compatible_p(typeof(expr), signed short) || \
WARNING: line over 80 characters
#54: FILE: include/qemu/atomic.h:45:
+ __builtin_types_compatible_p(typeof(expr), const signed short) || \
WARNING: line over 80 characters
#55: FILE: include/qemu/atomic.h:46:
+ __builtin_types_compatible_p(typeof(expr), volatile signed short) || \
WARNING: Use of volatile is usually wrong: see Documentation/volatile-considered-harmful.txt
#55: FILE: include/qemu/atomic.h:46:
+ __builtin_types_compatible_p(typeof(expr), volatile signed short) || \
WARNING: line over 80 characters
#56: FILE: include/qemu/atomic.h:47:
+ __builtin_types_compatible_p(typeof(expr), const volatile signed short), \
WARNING: Use of volatile is usually wrong: see Documentation/volatile-considered-harmful.txt
#56: FILE: include/qemu/atomic.h:47:
+ __builtin_types_compatible_p(typeof(expr), const volatile signed short), \
WARNING: line over 80 characters
#57: FILE: include/qemu/atomic.h:48:
+ (signed short)1, \
WARNING: line over 80 characters
#58: FILE: include/qemu/atomic.h:49:
+ __builtin_choose_expr( \
WARNING: line over 80 characters
#59: FILE: include/qemu/atomic.h:50:
+ __builtin_types_compatible_p(typeof(expr), unsigned short) || \
WARNING: line over 80 characters
#60: FILE: include/qemu/atomic.h:51:
+ __builtin_types_compatible_p(typeof(expr), const unsigned short) || \
WARNING: line over 80 characters
#61: FILE: include/qemu/atomic.h:52:
+ __builtin_types_compatible_p(typeof(expr), volatile unsigned short) || \
WARNING: Use of volatile is usually wrong: see Documentation/volatile-considered-harmful.txt
#61: FILE: include/qemu/atomic.h:52:
+ __builtin_types_compatible_p(typeof(expr), volatile unsigned short) || \
WARNING: line over 80 characters
#62: FILE: include/qemu/atomic.h:53:
+ __builtin_types_compatible_p(typeof(expr), const volatile unsigned short), \
WARNING: Use of volatile is usually wrong: see Documentation/volatile-considered-harmful.txt
#62: FILE: include/qemu/atomic.h:53:
+ __builtin_types_compatible_p(typeof(expr), const volatile unsigned short), \
WARNING: line over 80 characters
#63: FILE: include/qemu/atomic.h:54:
+ (unsigned short)1, \
ERROR: spaces required around that '+' (ctx:VxV)
#64: FILE: include/qemu/atomic.h:55:
+ (expr)+0)))))
^
total: 1 errors, 34 warnings, 90 lines checked
Your patch has style problems, please review. If any of these errors
are false positives report them to the maintainer, see
CHECKPATCH in MAINTAINERS.
=== OUTPUT END ===
Test command exited with code: 1
^ permalink raw reply [flat|nested] 2+ messages in thread
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2016-08-08 12:19 [Qemu-devel] [PATCH for 2.7] atomic: strip "const" from variables declared with typeof Paolo Bonzini
2016-08-08 12:23 ` no-reply
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