Merge pull request dabeaz#168 from laerreal/fixup_infinite_recursion

Fixup infinite recursion in CPP during macro arguments expansion

ply/cpp.py

@@ -436,7 +436,7 @@ def macro_prescan(self,macro):
     # representing the replacement macro tokens
     # ----------------------------------------------------------------------
 
-    def macro_expand_args(self,macro,args):
+    def macro_expand_args(self,macro,args,expanded):
         # Make a copy of the macro token sequence
         rep = [copy.copy(_x) for _x in macro.value]
 
@@ -460,16 +460,16 @@ def macro_expand_args(self,macro,args):
         # has been sorted in reverse order of patch location since replacements will cause the
         # size of the replacement sequence to expand from the patch point.
 
-        expanded = { }
+        expanded_args = { }
         for ptype, argnum, i in macro.patch:
             # Concatenation.   Argument is left unexpanded
             if ptype == 'c':
                 rep[i:i+1] = args[argnum]
             # Normal expansion.  Argument is macro expanded first
             elif ptype == 'e':
-                if argnum not in expanded:
-                    expanded[argnum] = self.expand_macros(args[argnum])
-                rep[i:i+1] = expanded[argnum]
+                if argnum not in expanded_args:
+                    expanded_args[argnum] = self.expand_macros(args[argnum],expanded)
+                rep[i:i+1] = expanded_args[argnum]
 
         # Get rid of removed comma if necessary
         if comma_patch:
@@ -530,7 +530,7 @@ def expand_macros(self,tokens,expanded=None):
                                         del args[len(m.arglist):]
 
                                 # Get macro replacement text
-                                rep = self.macro_expand_args(m,args)
+                                rep = self.macro_expand_args(m,args,expanded)
                                 rep = self.expand_macros(rep,expanded)
                                 for r in rep:
                                     r.lineno = t.lineno

test/testcpp.py

@@ -45,6 +45,22 @@ def __test_preprocessing(self, in_, expected, time_limit = 1.0):
         else:
             self.assertMultiLineEqual(out, expected)
 
+    def test_infinite_argument_expansion(self):
+        # CPP does not drags set of currently expanded macros through macro
+        # arguments expansion. If there is a match between an argument value
+        # and name of an already expanded macro then CPP falls into infinite
+        # recursion.
+        self.__test_preprocessing("""\
+#define a(x) x
+#define b a(b)
+b
+"""         , """\
+
+
+b"""
+        )
+
+
     def test_concatenation(self):
         self.__test_preprocessing("""\
 #define a(x) x##_