Re: [ovs-dev] [PATCH v4 03/15] util: add helpers to overload SAFE macro

Wed, 23 Mar 2022 00:20:32 -0700 


On 3/18/22 14:19, Eelco Chaudron wrote:



On 9 Mar 2022, at 17:10, Adrian Moreno wrote:


Having both LONG and SHORT versions of the SAFE macros with different
names is not very convenient. Add helpers that facilitate overloading
such macros using a single name.

In order to work around a known issue in MSVC [1], an indirection layer
has to be introduced.

[1]
https://developercommunity.visualstudio.com/t/-va-args-seems-to-be-trated-as-a-single-parameter/460154

Acked-by: Dumitru Ceara <[email protected]>
Signed-off-by: Adrian Moreno <[email protected]>
---


This looks good to me!

Acked-by: Eelco Chaudron <[email protected]>



Thanks for the review Eelco.



Small nit, do we need to update the date in the copyright notice? I keep 
forgetting if we do or do not. But I guess not, as I do not see it in other 
files.



I honestly have no idea. Maybe Ilya can help here?


  include/openvswitch/util.h | 21 +++++++++++++++++++++
  1 file changed, 21 insertions(+)

diff --git a/include/openvswitch/util.h b/include/openvswitch/util.h
index 157f8cecd..8184dd3d3 100644
--- a/include/openvswitch/util.h
+++ b/include/openvswitch/util.h
@@ -268,6 +268,27 @@ OVS_NO_RETURN void ovs_assert_failure(const char *, const 
char *, const char *);
  #define UPDATE_MULTIVAR_SAFE_LONG(VAR, NEXT_VAR)                              
\
      UPDATE_MULTIVAR(VAR, ITER_VAR(NEXT_VAR))

+/* Helpers to allow overloading the *_SAFE iterator macros and select either
+ * the LONG or the SHORT version depending on the number of arguments.
+ */
+#define GET_SAFE_MACRO2(_1, _2, NAME, ...) NAME
+#define GET_SAFE_MACRO3(_1, _2, _3, NAME, ...) NAME
+#define GET_SAFE_MACRO4(_1, _2, _3, _4, NAME, ...) NAME
+#define GET_SAFE_MACRO5(_1, _2, _3, _4, _5, NAME, ...) NAME
+#define GET_SAFE_MACRO6(_1, _2, _3, _4, _5, _6, NAME, ...) NAME
+#define GET_SAFE_MACRO(MAX_ARGS) GET_SAFE_MACRO ## MAX_ARGS
+
+/* MSVC treats __VA_ARGS__ as a simple token in argument lists. Introduce
+ * a level of indirection to work around that. */
+#define EXPAND_MACRO(name, args) name args
+
+/* Overload the LONG and the SHORT version of the macros. MAX_ARGS is the
+ * maximum number of arguments (i.e: the number of arguments of the LONG
+ * version). */
+#define OVERLOAD_SAFE_MACRO(LONG, SHORT, MAX_ARGS, ...) \
+        EXPAND_MACRO(GET_SAFE_MACRO(MAX_ARGS), \
+                     (__VA_ARGS__, LONG, SHORT))(__VA_ARGS__)
+
  /* Returns the number of elements in ARRAY. */
  #define ARRAY_SIZE(ARRAY) __ARRAY_SIZE(ARRAY)

--
2.34.1

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--
Adrián Moreno

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