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To: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
Cc: dev@dpdk.org, Pallavi Kadam <pallavi.kadam@intel.com>,
Dmitry Malloy <dmitrym@microsoft.com>,
Narcisa Ana Maria Vasile <navasile@linux.microsoft.com>,
Ray Kinsella <mdr@ashroe.eu>, Neil Horman <nhorman@tuxdriver.com>
References: <20210303225121.16146-1-dmitry.kozliuk@gmail.com>
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From: Ferruh Yigit <ferruh.yigit@intel.com>
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Date: Thu, 20 May 2021 17:04:06 +0100
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Subject: Re: [dpdk-dev] [PATCH] doc: announce renaming of rte_ether_hdr
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On 5/20/2021 4:50 PM, Dmitry Kozlyuk wrote:
> 2021-05-20 16:27 (UTC+0100), Ferruh Yigit:
>> On 5/20/2021 4:06 PM, Dmitry Kozlyuk wrote:
>>> 2021-05-20 15:24 (UTC+0100), Ferruh Yigit:
>>>> On 3/3/2021 10:51 PM, Dmitry Kozlyuk wrote:
>>> [...]
>>>>>
>>>>> It is not mandatory to rename `d_addr`, this is for consistency only.
>>>>> Naming in `rte_ether_hdr` will also resemble `rte_ipv4/6_hdr`.
>>>>>
>>>>> Workaround is to define `struct rte_ether_hdr` in such a away that
>>>>> it can be used with or without `s_addr` macro (as defined on Windows)
>>>>> This can be done for Windows only or for all platforms to save space.
>>>>>
>>>>> #pragma push_macro("s_addr")
>>>>> #ifdef s_addr
>>>>> #undef s_addr
>>>>> #endif
>>>>>
>>>>> struct rte_ether_hdr {
>>>>> struct rte_ether_addr d_addr; /**< Destination address. */
>>>>> RTE_STD_C11
>>>>> union {
>>>>> struct rte_ether_addr s_addr; /**< Source address. */
>>>>> struct {
>>>>> struct rte_ether_addr S_un;
>>>>> /**< MUST NOT be used directly, only via s_addr */
>>>>> } S_addr;
>>>>> /*< MUST NOT be used directly, only via s_addr */
>>>>> };
>>>>> uint16_t ether_type; /**< Frame type. */
>>>>> } __rte_aligned(2);
>>>>>
>>>>> #pragma pop_macro("s_addr")
>>>>>
>>>>
>>>> What is the problem with the workaround, why we can't live with it?
>>>>
>>>> It requires an order in include files, right?
>>>
>>> There's no problem except a tricky structure definition with fields that
>>> violate DPDK coding rules. It works with any include order.
>>>
>>> Will fix typos in v3, thanks.
>>>
>>
>> For following case, won't compiler take 's_addr' as macro?
>>
>> #include <rte_ether.h>
>> #include <winsock2.h>
>> struct rte_ether_hdr eh;
>> /* eh.s_addr.addr_bytes[0] = 0;
>>
>
> Yes, it will. The macro will expand to `S_addr.S_un` and compile successfully.
will 'eh.S_addr.S_un.addr_bytes[0] = 0;' compile successfully?
> In theory, Microsoft can change the definition of `s_addr`, and while I doubt
> they will, it's a valid concern and a reason to remove workaround in 21.11.
>