--- a/mfbt/MacroArgs.h
+++ b/mfbt/MacroArgs.h
@@ -11,65 +11,74 @@
#ifndef mozilla_MacroArgs_h
#define mozilla_MacroArgs_h
// Concatenates pre-processor tokens in a way that can be used with __LINE__.
#define MOZ_CONCAT2(x, y) x ## y
#define MOZ_CONCAT(x, y) MOZ_CONCAT2(x, y)
/*
+ * MOZ_ARG_COUNT(...) counts the number of variadic arguments.
+ * You must pass in between 0 and 50 (inclusive) variadic arguments.
+ * For example:
+ *
+ * MOZ_ARG_COUNT() expands to 0
+ * MOZ_ARG_COUNT(a) expands to 1
+ * MOZ_ARG_COUNT(a, b) expands to 2
+ *
+ * Implementation notes:
+ * The `##__VA_ARGS__` form is a GCC extension that removes the comma if
+ * __VA_ARGS__ is empty. It is supported by Clang too. MSVC ignores ##,
+ * and its default behavior is already to strip the comma when __VA_ARGS__
+ * is empty.
+ *
+ * So MOZ_MACROARGS_ARG_COUNT_HELPER() expands to
+ * (_, 50, 49, ...)
+ * MOZ_MACROARGS_ARG_COUNT_HELPER(a) expands to
+ * (_, a, 50, 49, ...)
+ * etc.
+ */
+#define MOZ_ARG_COUNT(...) \
+ MOZ_MACROARGS_ARG_COUNT_HELPER2(MOZ_MACROARGS_ARG_COUNT_HELPER(__VA_ARGS__))
+
+#define MOZ_MACROARGS_ARG_COUNT_HELPER(...) (_, ##__VA_ARGS__, \
+ 50, 49, 48, 47, 46, 45, 44, 43, 42, 41, \
+ 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, \
+ 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, \
+ 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, \
+ 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
+
+#define MOZ_MACROARGS_ARG_COUNT_HELPER2(aArgs) \
+ MOZ_MACROARGS_ARG_COUNT_HELPER3 aArgs
+
+#define MOZ_MACROARGS_ARG_COUNT_HELPER3(a0, \
+ a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, \
+ a11, a12, a13, a14, a15, a16, a17, a18, a19, a20, \
+ a21, a22, a23, a24, a25, a26, a27, a28, a29, a30, \
+ a31, a32, a33, a34, a35, a36, a37, a38, a39, a40, \
+ a41, a42, a43, a44, a45, a46, a47, a48, a49, a50, \
+ a51, ...) a51
+
+/*
* MOZ_PASTE_PREFIX_AND_ARG_COUNT(aPrefix, ...) counts the number of variadic
* arguments and prefixes it with |aPrefix|. For example:
*
* MOZ_PASTE_PREFIX_AND_ARG_COUNT(, foo, 42) expands to 2
* MOZ_PASTE_PREFIX_AND_ARG_COUNT(A, foo, 42, bar) expands to A3
* MOZ_PASTE_PREFIX_AND_ARG_COUNT(A) expands to A0
* MOZ_PASTE_PREFIX_AND_ARG_COUNT() expands to 0, but MSVC warns there
* aren't enough arguments given.
*
* You must pass in between 0 and 50 (inclusive) variadic arguments, past
* |aPrefix|.
- *
- * The `##__VA_ARGS__` form is a GCC extension that removes the comma if
- * __VA_ARGS__ is empty. It is supported by Clang too. MSVC ignores ##,
- * and its default behavior is already to strip the comma when __VA_ARGS__
- * is empty.
- *
- * So MOZ_MACROARGS_ARG_COUNT_HELPER(prefix) expands to
- * (_, prefix50, prefix49, ...)
- * MOZ_MACROARGS_ARG_COUNT_HELPER(prefix, a) expands to
- * (_, a, prefix50, prefix49, ...)
- * etc.
*/
+#define MOZ_PASTE_PREFIX_AND_ARG_COUNT_GLUE(a, b) a b
#define MOZ_PASTE_PREFIX_AND_ARG_COUNT(aPrefix, ...) \
- MOZ_MACROARGS_ARG_COUNT_HELPER2( \
- MOZ_MACROARGS_ARG_COUNT_HELPER(aPrefix, ##__VA_ARGS__))
-
-#define MOZ_MACROARGS_ARG_COUNT_HELPER(aPrefix, ...) (_, ##__VA_ARGS__, \
- aPrefix##50, aPrefix##49, aPrefix##48, aPrefix##47, aPrefix##46, \
- aPrefix##45, aPrefix##44, aPrefix##43, aPrefix##42, aPrefix##41, \
- aPrefix##40, aPrefix##39, aPrefix##38, aPrefix##37, aPrefix##36, \
- aPrefix##35, aPrefix##34, aPrefix##33, aPrefix##32, aPrefix##31, \
- aPrefix##30, aPrefix##29, aPrefix##28, aPrefix##27, aPrefix##26, \
- aPrefix##25, aPrefix##24, aPrefix##23, aPrefix##22, aPrefix##21, \
- aPrefix##20, aPrefix##19, aPrefix##18, aPrefix##17, aPrefix##16, \
- aPrefix##15, aPrefix##14, aPrefix##13, aPrefix##12, aPrefix##11, \
- aPrefix##10, aPrefix##9, aPrefix##8, aPrefix##7, aPrefix##6, \
- aPrefix##5, aPrefix##4, aPrefix##3, aPrefix##2, aPrefix##1, aPrefix##0)
-
-#define MOZ_MACROARGS_ARG_COUNT_HELPER2(aArgs) \
- MOZ_MACROARGS_ARG_COUNT_HELPER3 aArgs
-
-#define MOZ_MACROARGS_ARG_COUNT_HELPER3(a0, \
- a1, a2, a3, a4, a5, a6, a7, a8, a9, a10, \
- a11, a12, a13, a14, a15, a16, a17, a18, a19, a20, \
- a21, a22, a23, a24, a25, a26, a27, a28, a29, a30, \
- a31, a32, a33, a34, a35, a36, a37, a38, a39, a40, \
- a41, a42, a43, a44, a45, a46, a47, a48, a49, a50, \
- a51, ...) a51
+ MOZ_PASTE_PREFIX_AND_ARG_COUNT_GLUE( \
+ MOZ_CONCAT, (aPrefix, MOZ_ARG_COUNT(__VA_ARGS__)))
/*
* MOZ_ARGS_AFTER_N expands to its arguments excluding the first |N|
* arguments. For example:
*
* MOZ_ARGS_AFTER_2(a, b, c, d) expands to: c, d
*/
#define MOZ_ARGS_AFTER_1(a1, ...) __VA_ARGS__
