On 12/4/2014 9:35 PM, Michael Qiu wrote:
> 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>
> ---
> v3 --> v2:
> use uintptr_t instead of unsigned long to
> save pointer.
>
> v2 --> v1:
> Workaround solution instead of shut off the
> gcc params.
>
> 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..cda3436 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;
> + uintptr_t ptr = (uintptr_t)buf;
> + const uint16_t *u16 = (const uint16_t *)ptr;
> uint32_t sum = 0;
>
> while (len >= (sizeof(*u16) * 4)) {
This workaround is to solve the compile issue of GCC strict-aliasing(Two
different type pointers should not be point to the same memory address).
For GCC 4.4.7 it will definitely occurs if flags "-fstrict-aliasing"
and "-Wall" used.
Thanks,
Michael
