> From: Andre Muezerie [mailto:andre...@linux.microsoft.com] > Sent: Tuesday, 19 November 2024 05.35 > > From: Tyler Retzlaff <roret...@linux.microsoft.com> > > MSVC struct packing is not compatible with GCC. Provide a macro that > can be used to push existing pack value and sets packing to 1-byte. > The existing __rte_packed macro is then used to restore the pack value > prior to the push. > > Instead of providing macros exclusively for MSVC and for GCC the > existing macro is deliberately utilized to trigger a warning if no > existing packing has been pushed allowing easy identification of > locations where the __rte_msvc_pack is missing. > > Signed-off-by: Tyler Retzlaff <roret...@linux.microsoft.com> > --- > lib/eal/include/rte_common.h | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/lib/eal/include/rte_common.h > b/lib/eal/include/rte_common.h > index 4d299f2b36..409890863e 100644 > --- a/lib/eal/include/rte_common.h > +++ b/lib/eal/include/rte_common.h > @@ -103,8 +103,10 @@ typedef uint16_t unaligned_uint16_t; > * Force a structure to be packed > */ > #ifdef RTE_TOOLCHAIN_MSVC > -#define __rte_packed > +#define __rte_msvc_pack __pragma(pack(push, 1)) > +#define __rte_packed __pragma(pack(pop)) > #else > +#define __rte_msvc_pack > #define __rte_packed __attribute__((__packed__)) > #endif > > -- > 2.47.0.vfs.0.3
Before proceeding with this, can we please discuss the alternative, proposed here: https://inbox.dpdk.org/dev/cajfav8ystgibbe+nkt9mc30r0+zp64_kgurhozqd90rd2hx...@mail.gmail.com/ The definition of the packing macro in OVS, for reference: https://github.com/openvswitch/ovs/blob/main/include/openvswitch/compiler.h#L209 The current solution requires __rte_packed to be placed at the end of a structure, although __attribute__((packed)) is normally allowed at the beginning (between the "struct" tag and the name of the structure), which introduces a high risk of contributors placing it "incorrectly", thus causing errors. I have a strong preference for an __RTE_PACKED(decl) variant. Here's a third alternative: #ifdef RTE_TOOLCHAIN_MSVC #define __rte_msvc_pack_begin __pragma(pack(push, 1)) #define __rte_msvc_pack_end __pragma(pack(pop)) #else #define __rte_msvc_pack_begin #define __rte_msvc_pack_end #endif The third alternative is also problematic, e.g. if a contributor forgets the _end after the structure declaration, or adds another structure declaration before the _end. -Morten
