Simplify declarations of x-macro FLATBUFFERS_TD (#5638)

1 files changed, 19 insertions, 7 deletions

diff --git a/include/flatbuffers/idl.h b/include/flatbuffers/idl.h
index 5c7fc11d..4e8f71d3 100644
--- a/include/flatbuffers/idl.h
+++ b/include/flatbuffers/idl.h
@@ -91,6 +91,20 @@ switch (type) {
 }
 */
 
+// If not all FLATBUFFERS_GEN_() arguments are necessary for implementation 
+// of FLATBUFFERS_TD, you can use a variadic macro (with __VA_ARGS__ if needed).
+// In the above example, only CTYPE is used to generate the code, it can be rewritten:
+
+/*
+switch (type) {
+  #define FLATBUFFERS_TD(ENUM, IDLTYPE, CTYPE, ...) \
+    case BASE_TYPE_ ## ENUM: \
+      // do something specific to CTYPE here
+    FLATBUFFERS_GEN_TYPES(FLATBUFFERS_TD)
+  #undef FLATBUFFERS_TD
+}
+*/
+
 #define FLATBUFFERS_GEN_TYPES(TD) \
         FLATBUFFERS_GEN_TYPES_SCALAR(TD) \
         FLATBUFFERS_GEN_TYPES_POINTER(TD) \
@@ -101,17 +115,15 @@ switch (type) {
 __extension__  // Stop GCC complaining about trailing comma with -Wpendantic.
 #endif
 enum BaseType {
-  #define FLATBUFFERS_TD(ENUM, IDLTYPE, CTYPE, JTYPE, GTYPE, NTYPE, PTYPE, \
-                         RTYPE, KTYPE) \
-      BASE_TYPE_ ## ENUM,
+  #define FLATBUFFERS_TD(ENUM, ...) \
+    BASE_TYPE_ ## ENUM,
     FLATBUFFERS_GEN_TYPES(FLATBUFFERS_TD)
   #undef FLATBUFFERS_TD
 };
 
-#define FLATBUFFERS_TD(ENUM, IDLTYPE, CTYPE, JTYPE, GTYPE, NTYPE, PTYPE, \
-                       RTYPE, KTYPE) \
-    static_assert(sizeof(CTYPE) <= sizeof(largest_scalar_t), \
-                  "define largest_scalar_t as " #CTYPE);
+#define FLATBUFFERS_TD(ENUM, IDLTYPE, CTYPE, ...) \
+  static_assert(sizeof(CTYPE) <= sizeof(largest_scalar_t), \
+                "define largest_scalar_t as " #CTYPE);
   FLATBUFFERS_GEN_TYPES(FLATBUFFERS_TD)
 #undef FLATBUFFERS_TD