[dpdk-dev] [PATCH v3 08/10] eal/windows: fix rte_page_sizes with Clang on Windows

[Ray Kinsella]

On 15/04/2020 12:17, Jerin Jacob wrote:
> On Wed, Apr 15, 2020 at 4:39 PM Dmitry Kozlyuk <dmitry.kozliuk at gmail.com> wrote:
>>
>>
>>
>>> On Wed, Apr 15, 2020 at 4:02 PM Dmitry Kozlyuk <dmitry.kozliuk at gmail.com> wrote:
>>>>
>>>>> On Wed, Apr 15, 2020 at 1:16 AM Dmitry Kozlyuk <dmitry.kozliuk at gmail.com> wrote:
>>>>>>
>>>>>> Clang on Windows follows MS ABI where enum values are limited to 2^31-1.
>>>>>> Enum rte_page_size has members valued above this limit, which get
>>>>>> wrapped to zero, resulting in compilation error (duplicate values in
>>>>>> enum). Using MS ABI is mandatory for Windows EAL to call Win32 APIs.
>>>>>>
>>>>>> Define these values outside of the enum for Clang on Windows only.
>>>>>> This does not affect runtime, because Windows doesn't run on machines
>>>>>> with 4GiB and 16GiB hugepages.
>>>>>>
>>>>>> Signed-off-by: Dmitry Kozlyuk <dmitry.kozliuk at gmail.com>
>>>>>> ---
>>>>>>  lib/librte_eal/include/rte_memory.h | 6 ++++++
>>>>>>  1 file changed, 6 insertions(+)
>>>>>>
>>>>>> diff --git a/lib/librte_eal/include/rte_memory.h b/lib/librte_eal/include/rte_memory.h
>>>>>> index 1b7c3e5df..3ec673f51 100644
>>>>>> --- a/lib/librte_eal/include/rte_memory.h
>>>>>> +++ b/lib/librte_eal/include/rte_memory.h
>>>>>> @@ -34,8 +34,14 @@ enum rte_page_sizes {
>>>>>>         RTE_PGSIZE_256M  = 1ULL << 28,
>>>>>>         RTE_PGSIZE_512M  = 1ULL << 29,
>>>>>>         RTE_PGSIZE_1G    = 1ULL << 30,
>>>>>> +/* Work around Clang on Windows being limited to 32-bit underlying type. */
>>>>>
>>>>> It does look like "enum rte_page_sizes" NOT used as enum anywhere.
>>>>>
>>>>> [master][dpdk.org] $ grep -ri "enum rte_page_sizes" lib/
>>>>> lib/librte_eal/include/rte_memory.h:enum rte_page_sizes {
>>>>>
>>>>> Why not remove this workaround and define all items as #define to
>>>>> avoid below ifdef clutter.
>>>>>
>>>>>> +#if !defined(RTE_CC_CLANG) || !defined(RTE_EXEC_ENV_WINDOWS)
>>>>>
>>>>> See above.
>>>>>
>>>>>>         RTE_PGSIZE_4G    = 1ULL << 32,
>>>>>>         RTE_PGSIZE_16G   = 1ULL << 34,
>>>>>> +#else
>>>>>> +#define RTE_PGSIZE_4G  (1ULL << 32)
>>>>>> +#define RTE_PGSIZE_16G (1ULL << 34)
>>>>>> +#endif
>>>>>>  };
>>>>>>
>>>>>>  #define SOCKET_ID_ANY -1                    /**< Any NUMA socket. */
>>>>>> --
>>>>>> 2.25.1
>>>>>>
>>>>
>>>> This is a public header and removing enum rte_page_sizes will break API.
>>>> Moving members out of enum while keeping enum itself might break compilation
>>>> because of integer constants being converted to enum (with -Werror).
>>>
>>> If none of the public API is using this enum then I think, we may not
>>> need to make this enum as public.
>>
>> Agreed.
>>
>>> Since it has ULL, I believe both cases(enum or define), it will be
>>> treated as unsigned long long. ie. NO ABI breakage.
>>
>> I was talking about API only (compile-time compatibility). Getting rid of
>> #ifdef and workarounds sounds right, we'll just need a notice in release
>> notes.
> 
> Good to check ./devtools/check-abi.sh for any ABI breakage.

or something like this to cover all the bases.
DPDK_ABI_REF_DIR=/build/dpdk/reference/ DPDK_ABI_REF_VERSION=v20.02 ./devtools/test-meson-builds.sh


>>
>> --
>> Dmitry Kozlyuk