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

[Thomas Monjalon]

02/08/2021 15:48, Akhil Goyal:
> > 2021-08-02 12:45 (UTC+0000), Akhil Goyal:
> > > > 21/07/2021 21:55, Dmitry Kozlyuk:
> > > > > 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 at gmail.com>
> > > > > Acked-by: Khoa To <khot at microsoft.com>
[...]
> > > > Acked-by: Thomas Monjalon <thomas at monjalon.net>
> > > >
> > > Can we have a local variable named as min/max?
> > > If not, then I believe it is not a good idea.
> > 
> > Yes, except for inline functions in public headers.
> > The only problematic one I know of is this (rte_lru_x86.h):
> > 
> > static inline int
> > f_lru_pos(uint64_t lru_list)
> > {
> > 	__m128i lst = _mm_set_epi64x((uint64_t)-1, lru_list);
> > 	__m128i min = _mm_minpos_epu16(lst); /* <<< */
> > 	return _mm_extract_epi16(min, 1);
> > }
> > 
> > Fixing it breaks neither API nor ABI, thus no explicit deprecation notice.
> OK,
> Acked-by: Akhil Goyal <gakhil at marvell.com>

Applied, thanks.