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Re: [Qemu-devel] [PATCH 1/1] seqlock: Fix warning reg. incompatible cast
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH 1/1] seqlock: Fix warning reg. incompatible cast |
Date: |
Mon, 8 Aug 2016 11:05:15 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 |
On 07/08/2016 03:41, Pranith Kumar wrote:
> With the latest clang, we have the following warning. We are not using
> the const qualifier consistently in other functions. So remove it from
> the only one that uses it to fix the 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 qualifier
> s [-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); \
> ^~~~~
> /home/pranith/devops/code/qemu/include/qemu/compiler.h:62:43: note: expanded
> from macro 'unlikely'
> #define unlikely(x) __builtin_expect(!!(x), 0)
>
> Signed-off-by: Pranith Kumar <address@hidden>
This is a compiler bug, isn't it? Atomic loads of a const pointer
should be allowed.
Paolo
> ---
> include/qemu/seqlock.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/qemu/seqlock.h b/include/qemu/seqlock.h
> index 2e2be4c..aa4cf15 100644
> --- a/include/qemu/seqlock.h
> +++ b/include/qemu/seqlock.h
> @@ -55,7 +55,7 @@ static inline unsigned seqlock_read_begin(QemuSeqLock *sl)
> return ret & ~1;
> }
>
> -static inline int seqlock_read_retry(const QemuSeqLock *sl, unsigned start)
> +static inline int seqlock_read_retry(QemuSeqLock *sl, unsigned start)
> {
> /* Read other fields before reading final sequence. */
> smp_rmb();
>