FMT_FOR_EACH_NARG -> FMT_NARG.

format.h

@@ -2178,14 +2178,17 @@ inline void FormatDec(char *&buffer, T value) {
 #define FMT_CONCATENATE2(arg1, arg2)  arg1##arg2
 
 #define FMT_EXPAND(args) args
-#define FMT_FOR_EACH_NARG(...) FMT_FOR_EACH_NARG_(__VA_ARGS__, FMT_FOR_EACH_RSEQ_N())
-#define FMT_FOR_EACH_NARG_(...) FMT_EXPAND(FMT_FOR_EACH_ARG_N(__VA_ARGS__))
-#define FMT_FOR_EACH_ARG_N(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, N, ...) N
-#define FMT_FOR_EACH_RSEQ_N() 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0
+
+// Returns the number of arguments.
+// Based on https://groups.google.com/forum/#!topic/comp.std.c/d-6Mj5Lko_s.
+#define FMT_NARG(...) FMT_NARG_(__VA_ARGS__, FMT_RSEQ_N())
+#define FMT_NARG_(...) FMT_ARG_N(__VA_ARGS__)
+#define FMT_ARG_N(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, N, ...) N
+#define FMT_RSEQ_N() 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0
 
 #define FMT_FOR_EACH_(N, func, ...) FMT_CONCATENATE(FMT_FOR_EACH, N)(func, __VA_ARGS__)
 #define FMT_FOR_EACH(f, ...) \
-  FMT_EXPAND(FMT_FOR_EACH_(FMT_FOR_EACH_NARG(__VA_ARGS__), f, __VA_ARGS__))
+  FMT_EXPAND(FMT_FOR_EACH_(FMT_NARG(__VA_ARGS__), f, __VA_ARGS__))
 
 #define FMT_ADD_ARG_NAME(type, index) type arg##index
 #define FMT_GET_ARG_NAME(type, index) arg##index

test/macro-test.cc

@@ -49,6 +49,19 @@ TEST(UtilTest, ForEach) {
   }
 }
 
+TEST(UtilTest, NArg) {
+  EXPECT_EQ(1, FMT_NARG(a));
+  EXPECT_EQ(2, FMT_NARG(a, b));
+  EXPECT_EQ(3, FMT_NARG(a, b, c));
+  EXPECT_EQ(4, FMT_NARG(a, b, c, d));
+  EXPECT_EQ(5, FMT_NARG(a, b, c, d, e));
+  EXPECT_EQ(6, FMT_NARG(a, b, c, d, e, f));
+  EXPECT_EQ(7, FMT_NARG(a, b, c, d, e, f, g));
+  EXPECT_EQ(8, FMT_NARG(a, b, c, d, e, f, g, h));
+  EXPECT_EQ(9, FMT_NARG(a, b, c, d, e, f, g, h, i));
+  EXPECT_EQ(10, FMT_NARG(a, b, c, d, e, f, g, h, i, j));
+}
+
 int result;
 
 #define MAKE_TEST(func) \