2013-10-15 10:49:55

by Ramkumar Ramachandra

Subject: [PATCH] virtio tools: use ansi versions of asm and volatile

asm and volatile are provided for backward compatibility; use the ansi
versions __asm__ and __volatile__.

Cc: Rusty Russell <[email protected]>
Cc: Michael S. Tsirkin <[email protected]>
Signed-off-by: Ramkumar Ramachandra <[email protected]>
---
tools/virtio/asm/barrier.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/virtio/asm/barrier.h b/tools/virtio/asm/barrier.h
index aff61e1..b2fbbfc 100644
--- a/tools/virtio/asm/barrier.h
+++ b/tools/virtio/asm/barrier.h
@@ -1,5 +1,5 @@
#if defined(__i386__) || defined(__x86_64__)
-#define barrier() asm volatile("" ::: "memory")
+#define barrier() __asm__ __volatile__("" ::: "memory")
#define mb() __sync_synchronize()

#define smp_mb() mb()
--
1.8.4.477.g5d89aa9

2013-10-16 22:46:54

by Rusty Russell

Subject: Re: [PATCH] virtio tools: use ansi versions of asm and volatile

Ramkumar Ramachandra <[email protected]> writes:
> asm and volatile are provided for backward compatibility; use the ansi
> versions __asm__ and __volatile__.

Really? I don't see that in the gcc documentation. In fact, I didn't
know __volatile__ at all:

If you are writing a header file that should be includable in ISO C
programs, write `__asm__' instead of `asm'. *Note Alternate Keywords::.

We're not...

Cheers,
Rusty.

> Cc: Rusty Russell <[email protected]>
> Cc: Michael S. Tsirkin <[email protected]>
> Signed-off-by: Ramkumar Ramachandra <[email protected]>
> ---
> tools/virtio/asm/barrier.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/virtio/asm/barrier.h b/tools/virtio/asm/barrier.h
> index aff61e1..b2fbbfc 100644
> --- a/tools/virtio/asm/barrier.h
> +++ b/tools/virtio/asm/barrier.h
> @@ -1,5 +1,5 @@
> #if defined(__i386__) || defined(__x86_64__)
> -#define barrier() asm volatile("" ::: "memory")
> +#define barrier() __asm__ __volatile__("" ::: "memory")
> #define mb() __sync_synchronize()
>
> #define smp_mb() mb()
> --
> 1.8.4.477.g5d89aa9

2013-10-17 06:24:46

by Ramkumar Ramachandra

Subject: Re: [PATCH] virtio tools: use ansi versions of asm and volatile

Rusty Russell wrote:
> Ramkumar Ramachandra <[email protected]> writes:
>> asm and volatile are provided for backward compatibility; use the ansi
>> versions __asm__ and __volatile__.
>
> Really? I don't see that in the gcc documentation. In fact, I didn't
> know __volatile__ at all:

Try compiling the program with `gcc -ansi`, and you'll see that "asm"
and "volatile" are undeclared. The motivation for my patch comes from
barrier() being declared differently in compiler-gcc.h.

However, the tree is polluted with the non-ansi versions anyway;
compilers will continue to support them for decades. So, I'd request
you to drop the patch.

Thanks.