[dpdk-dev] [PATCH v2] test-pmd: Fix pointer aliasing error

[Ananyev, Konstantin]

> -----Original Message-----
> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Michael Qiu
> Sent: Thursday, December 04, 2014 3:29 AM
> To: dev at dpdk.org
> Subject: [dpdk-dev] [PATCH v2] test-pmd: Fix pointer aliasing error
> 
> 
> app/test-pmd/csumonly.c: In function ‘get_psd_sum’:
> build/include/rte_ip.h:161: error: dereferencing pointer ‘u16’
>         does break strict-aliasing rules
> build/include/rte_ip.h:157: note: initialized from here
>         ...
> 
> The root cause is that, compile enable strict aliasing by default,
> while in function rte_raw_cksum() try to convert 'const char *'
> to 'const uint16_t *'.
> 
> This patch is one workaround fix.
> 
> Signed-off-by: Michael Qiu <michael.qiu at intel.com>
> ---
>  lib/librte_net/rte_ip.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/librte_net/rte_ip.h b/lib/librte_net/rte_ip.h
> index 61e4457..f1c7087 100644
> --- a/lib/librte_net/rte_ip.h
> +++ b/lib/librte_net/rte_ip.h
> @@ -154,7 +154,8 @@ struct ipv4_hdr {
>  static inline uint16_t
>  rte_raw_cksum(const char *buf, size_t len)
>  {
> -	const uint16_t *u16 = (const uint16_t *)buf;
> +	unsigned long ptr = (unsigned long)buf;

I think better use uintptr_t here.
It is specially designed to be long enough to hold pointer value.

> +	const uint16_t *u16 = (const uint16_t *)ptr;
>  	uint32_t sum = 0;
> 
>  	while (len >= (sizeof(*u16) * 4)) {
> --
> 1.9.3