Re: [PATCH v3] net: fix build error with clang

Hi, 

-----Original Message-----
From: Yuanhan Liu [mailto:yuanhan.liu@linux.intel.com]
Sent: Tuesday, September 27, 2016 5:20 AM
To: dev@dpdk.org
Cc: Jerin Jacob <redacted>; Chen, Jing D
[off-list ref]; Liang, Cunming [off-list ref];
Richardson, Bruce [off-list ref]; Thomas Monjalon
[off-list ref]
Subject: Re: [PATCH v3] net: fix build error with clang

Can any PMD guys review it? It blocks a virtio patchset apply...

Thanks.

	--yliu

On Mon, Sep 26, 2016 at 12:29:13PM +0800, Yuanhan Liu wrote:

quoted

Interestingly, clang and gcc has different prototype for _mm_prefetch().
For gcc, we have

   _mm_prefetch (const void *__P, enum _mm_hint __I)

While for clang, it's

   #define _mm_prefetch(a, sel) (__builtin_prefetch((void *)(a), 0,
(sel)))

That's how the following error comes with clang:

   error: cast from 'const void *' to 'void *' drops const qualifier
   [-Werror,-Wcast-qual]
           _mm_prefetch((const void *)rused, _MM_HINT_T0);
   /usr/lib/llvm-3.8/bin/../lib/clang/3.8.0/include/xmmintrin.h:684:58:
   note: expanded from macro '_mm_prefetch'
            #define _mm_prefetch(a, sel) (__builtin_prefetch((void *)(a),
                                          0, (sel)))

What's weird is that the build was actaully Okay before. I met it
while apply Jerin's vector support for ARM patch set: he just move
this peiece of code to another file, nothing else changed.

This patch fix the issue when Jerin's patchset is applied. Thus, I
think it's still needed.

Similarly, make the same change to other _mm_prefetch users, just in
case this weird issue shows up again somehow later.

Fixes: fc3d66212fed ("virtio: add vector Rx")
Fixes: c95584dc2b18 ("ixgbe: new vectorized functions for Rx/Tx")
Fixes: 9ed94e5bb04e ("i40e: add vector Rx")
Fixes: 7092be8437bd ("fm10k: add vector Rx")

Cc: Jerin Jacob <redacted>
Cc: Chen Jing D(Mark) <redacted>
Cc: Cunming Liang <redacted>
Cc: Bruce Richardson <redacted>
CC: Thomas Monjalon <redacted>
Signed-off-by: Yuanhan Liu <redacted>

Acked-by: Jing Chen <redacted>