| Message ID | 20160824204424.14041-1-bobby.prani@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 24/08/2016 22:44, Pranith Kumar wrote: > This patch tries to do the Right Thing™ to test for C11 features, > which is to test __STDC_VERSION__. Compilers can provide atomics even for older standards, for example: $ echo '__STDC_VERSION__' | gcc -E -x c - -std=gnu99 | tail -1 199901L $ echo '__ATOMIC_RELAXED' | gcc -E -x c - -std=gnu99 | tail -1 0 Which is why the patch is not using __STDC_VERSION__. Unfortunately, the C standard does not define a feature macro for atomics; it provides __STDC_NO_ATOMICS__ but it is defined backwards. Thanks, Paolo > Signed-off-by: Pranith Kumar <bobby.prani@gmail.com> > --- > include/qemu/atomic.h | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/include/qemu/atomic.h b/include/qemu/atomic.h > index 43b0645..d313e6b 100644 > --- a/include/qemu/atomic.h > +++ b/include/qemu/atomic.h > @@ -60,7 +60,7 @@ > (unsigned short)1, \ > (expr)+0)))))) > > -#ifdef __ATOMIC_RELAXED > +#if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 201112L) > /* For C11 atomic ops */ > > /* Manual memory barriers > @@ -210,7 +210,7 @@ > #define atomic_and(ptr, n) ((void) __atomic_fetch_and(ptr, n, __ATOMIC_SEQ_CST)) > #define atomic_or(ptr, n) ((void) __atomic_fetch_or(ptr, n, __ATOMIC_SEQ_CST)) > > -#else /* __ATOMIC_RELAXED */ > +#else /* __STDC_VERSION__ */ > > /* > * We use GCC builtin if it's available, as that can use mfence on > @@ -405,5 +405,5 @@ > #define atomic_and(ptr, n) ((void) __sync_fetch_and_and(ptr, n)) > #define atomic_or(ptr, n) ((void) __sync_fetch_and_or(ptr, n)) > > -#endif /* __ATOMIC_RELAXED */ > +#endif /* __STDC_VERSION__ */ > #endif /* QEMU_ATOMIC_H */ >
diff --git a/include/qemu/atomic.h b/include/qemu/atomic.h index 43b0645..d313e6b 100644 --- a/include/qemu/atomic.h +++ b/include/qemu/atomic.h @@ -60,7 +60,7 @@ (unsigned short)1, \ (expr)+0)))))) -#ifdef __ATOMIC_RELAXED +#if defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 201112L) /* For C11 atomic ops */ /* Manual memory barriers @@ -210,7 +210,7 @@ #define atomic_and(ptr, n) ((void) __atomic_fetch_and(ptr, n, __ATOMIC_SEQ_CST)) #define atomic_or(ptr, n) ((void) __atomic_fetch_or(ptr, n, __ATOMIC_SEQ_CST)) -#else /* __ATOMIC_RELAXED */ +#else /* __STDC_VERSION__ */ /* * We use GCC builtin if it's available, as that can use mfence on @@ -405,5 +405,5 @@ #define atomic_and(ptr, n) ((void) __sync_fetch_and_and(ptr, n)) #define atomic_or(ptr, n) ((void) __sync_fetch_and_or(ptr, n)) -#endif /* __ATOMIC_RELAXED */ +#endif /* __STDC_VERSION__ */ #endif /* QEMU_ATOMIC_H */
This patch tries to do the Right Thing™ to test for C11 features, which is to test __STDC_VERSION__. Signed-off-by: Pranith Kumar <bobby.prani@gmail.com> --- include/qemu/atomic.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)