[dpdk-dev] [PATCH v4] doc: announce API changes for Windows compatibility

[Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>]

Windows headers define `s_addr`, `min`, and `max` as macros.
If DPDK headers are included after Windows ones, DPDK structure
definitions containing fields with these names get broken (example 1),
as well as any usage of such fields (example 2). If DPDK headers
undefined these macros, it could break consumer code (example 3).
It is proposed to rename structure fields in DPDK, because Win32 headers
are used more widely than DPDK, as a general-purpose platform compared
to domain-specific kit, and are harder to fix because of that.
Exact new names are left for further discussion.

Example 1:

    /* in DPDK public header included after windows.h */
    struct rte_type {
        int min;    /* ERROR: `min` is a macro */
    };

Example 2:

    #include <rte_ether.h>
    #include <winsock2.h>
    struct rte_ether_hdr eh;
    eh.s_addr.addr_bytes[0] = 0;    /* ERROR: `addr_s` is a macro */

Example 3:

    #include <winsock2.h>
    #include <rte_ether.h>
    struct in_addr addr;
    addr.s_addr = 0;      /* ERROR: there is no `s_addr` field,
                             and `s_addr` macro is undefined by DPDK. */

Commit 6c068dbd9fea ("net: work around s_addr macro on Windows")
modified definition of `struct rte_ether_hdr` to avoid the issue.
However, the workaround assumes `#define s_addr S_addr.S_un`
in Windows headers, which is not a part of official API.
It also complicates the definition of `struct rte_ether_hdr`.

Signed-off-by: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
Acked-by: Khoa To <khot@microsoft.com>
---
v4: improve wording (Akhil).
v3: fix typos (Ferruh), remove naming speculation,
    replace workaround snippet with commit reference.

 doc/guides/rel_notes/deprecation.rst | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/doc/guides/rel_notes/deprecation.rst b/doc/guides/rel_notes/deprecation.rst
index 9584d6bfd7..cc6e8db92c 100644
--- a/doc/guides/rel_notes/deprecation.rst
+++ b/doc/guides/rel_notes/deprecation.rst
@@ -147,3 +147,12 @@ Deprecation Notices
 * cmdline: ``cmdline`` structure will be made opaque to hide platform-specific
   content. On Linux and FreeBSD, supported prior to DPDK 20.11,
   original structure will be kept until DPDK 21.11.
+
+* net: ``s_addr`` and ``d_addr`` fields of ``rte_ether_hdr`` structure
+  will be renamed in DPDK 21.11 to avoid conflict with Windows Sockets headers.
+
+* compressdev: ``min`` and ``max`` fields of ``rte_param_log2_range`` structure
+  will be renamed in DPDK 21.11 to avoid conflict with Windows Sockets headers.
+
+* cryptodev: ``min`` and ``max`` fields of ``rte_crypto_param_range`` structure
+  will be renamed in DPDK 21.11 to avoid conflict with Windows Sockets headers.
-- 
2.29.3