[cfe-commits] r38761 - /cfe/cfe/trunk/Lex/MacroExpander.cpp

[sabre at cs.uiuc.edu]

Author: sabre
Date: Wed Jul 11 11:24:24 2007
New Revision: 38761

URL: http://llvm.org/viewvc/llvm-project?rev=38761&view=rev
Log:
Implement pasting of arguments that expand to no tokens.  This handles the
C99 "placemarker" concept.

Modified:
    cfe/cfe/trunk/Lex/MacroExpander.cpp

Modified: cfe/cfe/trunk/Lex/MacroExpander.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/cfe/trunk/Lex/MacroExpander.cpp?rev=38761&r1=38760&r2=38761&view=diff

==============================================================================
--- cfe/cfe/trunk/Lex/MacroExpander.cpp (original)
+++ cfe/cfe/trunk/Lex/MacroExpander.cpp Wed Jul 11 11:24:24 2007
@@ -377,9 +377,23 @@
       }
       
       // FIXME: Handle comma swallowing GNU extension.
-      // FIXME: Handle 'placemarker' stuff.
-      assert(0 && "FIXME: handle empty arguments!");
-      //ResultToks.push_back(CurTok);
+      
+      // If an empty argument is on the LHS or RHS of a paste, the standard (C99
+      // 6.10.3.3p2,3) calls for a bunch of placemarker stuff to occur.  We
+      // implement this by eating ## operators when a LHS or RHS expands to
+      // empty.
+      if (PasteAfter) {
+        // Discard the argument token and skip (don't copy to the expansion
+        // buffer) the paste operator after it.
+        ++i;
+        continue;
+      }
+      
+      // If this is on the RHS of a paste operator, we've already copied the
+      // paste operator to the ResultToks list.  Remove it.
+      assert(PasteBefore && ResultToks.back().getKind() == tok::hashhash);
+      ResultToks.pop_back();
+      continue;
     }
   }