Re: [dpdk-dev] [PATCH v3] Fix two compile issues with i686 platform

[Bruce Richardson <bruce.richardson@intel.com>]

On Fri, Dec 05, 2014 at 09:22:05AM -0500, Neil Horman wrote:
> On Fri, Dec 05, 2014 at 04:31:47PM +0800, Chao Zhu wrote:
> > 
> > On 2014/12/4 17:12, Michael Qiu wrote:
> > >lib/librte_eal/linuxapp/eal/eal_memory.c:324:4: error: comparison
> > >is always false due to limited range of data type [-Werror=type-limits]
> > >     || (hugepage_sz == RTE_PGSIZE_16G)) {
> > >     ^
> > >cc1: all warnings being treated as errors
> > >
> > >lib/librte_eal/linuxapp/eal/eal.c(461): error #2259: non-pointer
> > >conversion from "long long" to "void *" may lose significant bits
> > >    RTE_PTR_ALIGN_CEIL((uintptr_t)addr, RTE_PGSIZE_16M);
> > >
> > >This was introuduced by commit b77b5639:
> > >         mem: add huge page sizes for IBM Power
> > >
> > >The root cause is that size_t and uintptr_t are 32-bit in i686
> > >platform, but RTE_PGSIZE_16M and RTE_PGSIZE_16G are always 64-bit.
> > >
> > >Define RTE_PGSIZE_16G only in 64 bit platform to avoid
> > >this issue.
> > >
> > >Signed-off-by: Michael Qiu <michael.qiu@intel.com>
> > >---
> > >  v3 ---> v2
> > >	Change RTE_PGSIZE_16G from ULL to UL
> > >	to keep all entries consistent
> > >
> > >  V2 ---> v1
> > >	Change two type entries to one, and
> > >	leave RTE_PGSIZE_16G only valid for
> > >	64-bit platform
> > >
> NACK, this is the wrong way to fix this problem.  Pagesizes are independent of
> architecutre.  While a system can't have a hugepage size that exceeds its
> virtual address limit, theres no need to do per-architecture special casing of
> page sizes here.  Instead of littering the code with ifdef RTE_ARCH_64
> everytime you want to check a page size, just convert the size_t to a uint64_t
> and you can allow all of the enumerated page types on all architecutres, and
> save yourself some ifdeffing in the process.
> 
> Neil

While I get your point, I find it distasteful to use a uint64_t for memory sizes,
when there is the size_t type defined for that particular purpose.
However, I suppose that reducing the number of #ifdefs compared to using the
"correct" datatypes for objects is a more practical optino - however distastful
I find it.

/Bruce