Re: [PATCH v2] librte_eal/common: Fix cast from pointer to integer of different size

[Pawel Wodkowski <pawelx.wodkowski-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

> -----Original Message-----
> From: Qiu, Michael
> Sent: Tuesday, March 03, 2015 11:00 AM
> To: Wodkowski, PawelX; dev-VfR2kkLFssw@public.gmane.org
> Subject: Re: [dpdk-dev] [PATCH v2] librte_eal/common: Fix cast from pointer to
> integer of different size
>
> On 3/3/2015 4:25 PM, Wodkowski, PawelX wrote:
> > On 2015-03-03 03:20, Michael Qiu wrote:
> >> /i686-native-linuxapp-gcc/include/rte_memcpy.h:592:23: error:
> >> cast from pointer to integer of different size
> >> [-Werror=pointer-to-int-cast]
> >>
> >>    dstofss = 16 - (int)((long long)(void *)dst & 0x0F) + 16;
> >>
> >> Type 'long long' is 64-bit in i686 platform while 'void *'
> >> is 32-bit.
> >>
> >> Signed-off-by: Michael Qiu <michael.qiu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> >> ---
> >> v2 --> v1:
> >> 	Remove unnecessary casting (void *)
> >>
> >>   lib/librte_eal/common/include/arch/x86/rte_memcpy.h | 4 ++--
> >>   1 file changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/lib/librte_eal/common/include/arch/x86/rte_memcpy.h
> b/lib/librte_eal/common/include/arch/x86/rte_memcpy.h
> >> index 7b2d382..85a5f4d 100644
> >> --- a/lib/librte_eal/common/include/arch/x86/rte_memcpy.h
> >> +++ b/lib/librte_eal/common/include/arch/x86/rte_memcpy.h
> >> @@ -589,12 +589,12 @@ COPY_BLOCK_64_BACK15:
> >>   	 * unaligned copy functions require up to 15 bytes
> >>   	 * backwards access.
> >>   	 */
> >> -	dstofss = 16 - (int)((long long)(void *)dst & 0x0F) + 16;
> >> +	dstofss = 16 - (int)((long)dst & 0x0F) + 16;
> >>   	n -= dstofss;
> >>   	rte_mov32((uint8_t *)dst, (const uint8_t *)src);
> >>   	src = (const uint8_t *)src + dstofss;
> >>   	dst = (uint8_t *)dst + dstofss;
> >> -	srcofs = (int)((long long)(const void *)src & 0x0F);
> >> +	srcofs = (int)((long)src & 0x0F);
> >>
> >>   	/**
> >>   	 * For aligned copy
> >>
> > I think you should use here size_t, (u)ptrdiff_t or (u)intptr_t as this
>
> Yes, but 'long' is enough, does it limit anything, or has any issue with
> multiple platforms?
>

Those types ((u)ptrdiff_t, (u)intptr_t) exists specially for 
pointer-to-int and int-to-pointer casts. Using integer primitives might 
produce further warnings/error in the future and need further patches 
fixing the same place.

Also why make offset variables signed and different type? This introduce 
a lot of unnecessary explicit and implicit casts or type promotions.

> > will be more portable.
> > Also type of dstofss and srcofs should be changed accordingly.
>
> No, I think, it should be offset.
>
> Thanks,
> Michael
> >


-- 
Pawel