Re: [PATCH] lib/lpm: use standard atomic_store_explicit

[Bruce Richardson <bruce.richardson@intel.com>]

On Wed, Dec 04, 2024 at 08:20:19AM -0800, Andre Muezerie wrote:
> On Wed, Dec 04, 2024 at 08:56:35AM +0100, David Marchand wrote:
> > Hello Andre,
> > 
> > On Wed, Dec 4, 2024 at 3:20 AM Andre Muezerie
> > <andremue@linux.microsoft.com> wrote:
> > >
> > > MSVC issues the warning below:
> > >
> > > ../lib/lpm/rte_lpm.c(297): warning C4013
> > >     '__atomic_store' undefined; assuming extern returning int
> > > ../lib/lpm/rte_lpm.c(298): error C2065:
> > >     '__ATOMIC_RELAXED': undeclared identifier
> > >
> > > The fix is to use standard atomic_store_explicit() instead of
> > > gcc specific __atomic_store().
> > > atomic_store_explicit() was already being used in other parts
> > > of DPDK and is compatible
> > > with many compilers, including MSVC.
> > >
> > > Signed-off-by: Andre Muezerie <andremue@linux.microsoft.com>
> > 
> > With this change, is there anything remaining that blocks this library
> > compilation with MSVC?
> > If not, please update meson.build so that CI can test lpm compilation
> > with MSVC on this patch (and that will detect regressions once
> > merged).
> > 
> > 
> > -- 
> > David Marchand
> 
> Hi David,
> 
> I'm eager to enable lpm to be compiled with MSVC. Even though
> this was the last issue I observed for this lib on my machine,
> lpm depends on hash, which depends on net, which depends on mbuf and
> mbuf is not enabled for MSVC yet.
> 
I was a bit curious about this dependency chain and decided to investigate
a bit. The "weak link" in this chain appears to me to be the link between
the hash library and the net library. Within the hash library, I believe
only the thash functionality depends on net, for definitions of the ipv6
headers and address fields.

If we want to break that dependency (temporarily, since net is pretty much
an essential DPDK lib), the following patch should work.

Regards,
/Bruce

diff --git a/lib/hash/meson.build b/lib/hash/meson.build
index e6cb1ebe3b..f9096edd67 100644
--- a/lib/hash/meson.build
+++ b/lib/hash/meson.build
@@ -6,24 +6,34 @@ headers = files(
         'rte_hash_crc.h',
         'rte_hash.h',
         'rte_jhash.h',
-        'rte_thash.h',
-        'rte_thash_gfni.h',
 )
 indirect_headers += files(
         'rte_crc_arm64.h',
         'rte_crc_generic.h',
         'rte_crc_sw.h',
         'rte_crc_x86.h',
-        'rte_thash_x86_gfni.h',
 )
 
 sources = files(
         'rte_cuckoo_hash.c',
         'rte_hash_crc.c',
         'rte_fbk_hash.c',
+)
+
+deps = ['rcu']
+
+if dpdk_conf.has('RTE_LIB_NET')
+    headers += files(
+        'rte_thash.h',
+        'rte_thash_gfni.h',
+    )
+    indirect_headers += files(
+        'rte_thash_x86_gfni.h',
+    )
+    sources += files(
         'rte_thash.c',
         'rte_thash_gfni.c',
         'rte_thash_gf2_poly_math.c',
-)
-
-deps = ['net', 'rcu']
+    )
+    deps += ['net']
+endif