Fixes issue #195, including test case

Additionally, cpp.Preprocessor.evalexpr is split into three methods: evalexpr, evalexpr_expanded, evalexpr_string, to allow for easier customization of the behaviour by overriding any of these stages in a derived class, maintaining the code of the others

2 files changed, 39 insertions, 2 deletions

diff --git a/ply/cpp.py b/ply/cpp.py
index de3956b..8565a6b 100644
--- a/ply/cpp.py
+++ b/ply/cpp.py
@@ -617,11 +617,21 @@ class Preprocessor(object):
                 del tokens[i+1:j+1]
             i += 1
         tokens = self.expand_macros(tokens)
+        return self.evalexpr_expanded(tokens)
+
+    # ----------------------------------------------------------------------
+    # evalexpr_expanded()
+    #
+    # Helper for evalexpr that evaluates the expression that had its macros
+    # and defined(...) expressions expanded by evalexpr
+    # ----------------------------------------------------------------------
+
+    def evalexpr_expanded(self, tokens):
         for i,t in enumerate(tokens):
             if t.type == self.t_ID:
                 tokens[i] = copy.copy(t)
                 tokens[i].type = self.t_INTEGER
-                tokens[i].value = self.t_INTEGER_TYPE("0L")
+                tokens[i].value = self.t_INTEGER_TYPE("0")
             elif t.type == self.t_INTEGER:
                 tokens[i] = copy.copy(t)
                 # Strip off any trailing suffixes
@@ -629,10 +639,19 @@ class Preprocessor(object):
                 while tokens[i].value[-1] not in "0123456789abcdefABCDEF":
                     tokens[i].value = tokens[i].value[:-1]
 
-        expr = "".join([str(x.value) for x in tokens])
+        return self.evalexpr_string("".join([str(x.value) for x in tokens]))
+
+    # ----------------------------------------------------------------------
+    # evalexpr_string()
+    #
+    # Helper for evalexpr that evaluates a string expression
+    # This implementation does basic C->python conversion and then uses eval()
+    # ----------------------------------------------------------------------
+    def evalexpr_string(self, expr):
         expr = expr.replace("&&"," and ")
         expr = expr.replace("||"," or ")
         expr = expr.replace("!"," not ")
+        expr = expr.replace(" not ="," !=")
         try:
             result = eval(expr)
         except Exception:
diff --git a/test/testcpp.py b/test/testcpp.py
index 45478ff..7e281a3 100644
--- a/test/testcpp.py
+++ b/test/testcpp.py
@@ -114,4 +114,22 @@ a"""
 a"""
         )
 
+    def test_evalexpr(self):
+        # #if 1 != 2 is not processed correctly; undefined values are converted
+        # to 0L instead of 0 (issue #195)
+        #
+        self.__test_preprocessing("""\
+#if (1!=0) && (!x || (!(1==2)))
+a;
+#else
+b;
+#endif
+"""
+            , """\
+
+a;
+
+"""
+        )
+
 main()