X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=folly%2FPreprocessor.h;h=800608d4afc3562569c50e048299ceca03ff7b18;hb=9276f2a5646a94eda765c92b171b98c499313213;hp=49bbc7109466f7307ebe46f084af2842d6b6b900;hpb=321542683a01c3f334047531e9b487f047129775;p=folly.git

diff --git a/folly/Preprocessor.h b/folly/Preprocessor.h
index 49bbc710..800608d4 100644
--- a/folly/Preprocessor.h
+++ b/folly/Preprocessor.h
@@ -16,8 +16,7 @@
 
 // @author: Andrei Alexandrescu
 
-#ifndef FOLLY_PREPROCESSOR_
-#define FOLLY_PREPROCESSOR_
+#pragma once
 
 /**
  * Necessarily evil preprocessor-related amenities.
@@ -47,6 +46,10 @@
 #define FB_THIRD(a, b, ...) __VA_ARGS__
 #endif
 
+// MSVC's preprocessor is a pain, so we have to
+// forcefully expand the VA args in some places.
+#define FB_VA_GLUE(a, b) a b
+
 /**
  * Helper macro that extracts the first argument out of a list of any
  * number of arguments.
@@ -58,7 +61,14 @@
  * number of arguments. If only one argument is given, it returns
  * that.
  */
+#ifdef _MSC_VER
+// GCC refuses to expand this correctly if this macro itself was
+// called with FB_VA_GLUE :(
+#define FB_ARG_2_OR_1(...) \
+  FB_VA_GLUE(FB_ARG_2_OR_1_IMPL, (__VA_ARGS__, __VA_ARGS__))
+#else
 #define FB_ARG_2_OR_1(...) FB_ARG_2_OR_1_IMPL(__VA_ARGS__, __VA_ARGS__)
+#endif
 // Support macro for the above
 #define FB_ARG_2_OR_1_IMPL(a, b, ...) b
 
@@ -73,6 +83,16 @@
  */
 #define FB_SINGLE_ARG(...) __VA_ARGS__
 
+/**
+ * Helper macro that just ignores its parameters.
+ */
+#define FOLLY_IGNORE(...)
+
+/**
+ * Helper macro that just ignores its parameters and inserts a semicolon.
+ */
+#define FOLLY_SEMICOLON(...) ;
+
 /**
  * FB_ANONYMOUS_VARIABLE(str) introduces an identifier starting with
  * str and ending with a number that varies with the line.
@@ -92,5 +112,3 @@
  * another macro expansion.
  */
 #define FB_STRINGIZE(x) #x
-
-#endif // FOLLY_PREPROCESSOR_