depgen.py: preprocessor: improve expression evaluation.

mkhelper/depgen/preprocessor.py

@@ -337,11 +337,23 @@ class MacroHandler(object):
         r"(defined\s*(\(\s*)?([a-zA-Z_]\w*)(?(2)\s*\)))"
     )
 
+    # an invalid identifier (used as a marker)
+    _invalid_identifier = " 0choke_me0 "
+
+    # a valid name for a variable
+    _valid_python_name = "choke_me"
+
     # matches object-like and function-like macro identifiers
     _re_identifier = re.compile(
-        r"(([a-zA-Z_]\w*)(\s*\(\s*(\w+(?:\s*,\s*\w+)*)?\s*\))?)"
+        "({0}|{1})".format(
+            _invalid_identifier,
+            r"([a-zA-Z_]\w*)\s*(\(\s*(?:\w+(?:\s*,\s*\w+)*\s*)?\))?",
+        )
     )
 
+    # matches empty identifier arguments
+    _re_empty_args = re.compile(r"^\(\s*\)$")
+
     __slots__ = ["_macros"]
 
     def __init__(self, predefined_macros=None):
@@ -358,7 +370,9 @@ def eval_defined(self, macro_name, negate=False):
         return 1 if bool(macro_name in self._macros) ^ negate else -1
 
     def eval_expression(self, expr):
-        prev_expr = expr
+        prev_expr = None
+
+        invalid_is_injected = False
         while 1:
             # replace calls to function "defined"
             defined_calls = re.findall(MacroHandler._re_defined_call, expr)
@@ -369,45 +383,88 @@ def eval_expression(self, expr):
 
             identifiers = re.findall(MacroHandler._re_identifier, expr)
 
-            for identifier in identifiers:
-                if identifier[1] == "defined":
+            for identifier, identifier_name, identifier_args in identifiers:
+                if identifier == MacroHandler._invalid_identifier:
+                    continue
+
+                if identifier_name == "defined":
+                    # this should never happen
                     return 0
 
-                macro = self._macros.get(identifier[1], None)
-                if identifier[2]:
-                    # potential call to a function
+                macro = self._macros.get(identifier_name, None)
+
+                if identifier_args:
+                    # expansion of a function-like identifier
+
                     if macro is None:
-                        # call to undefined function
-                        return 0
-                    elif macro[0] is not None:
-                        # we can't evaluate function-like macros
+                        # the respective macro is not defined, which normally
+                        # results in a preprocessor error
                         return 0
+
+                    if macro[0] is None:
+                        # the respective macro is an object-like one: replace
+                        # the name of the function-like identifier with the body
+                        # (value) of the macro
+                        identifier_repl = macro[1] + identifier_args
+                    elif MacroHandler._re_empty_args.match(identifier_args):
+                        # the argument list of the function-like identifier is
+                        # empty: replace the identifier with the body of the
+                        # function-like macro
+                        identifier_repl = macro[1]
                     else:
-                        # identifier is defined as object-like macro
-                        expr = expr.replace(
-                            identifier[0], macro[1] + identifier[2]
-                        )
+                        # we cannot expand function-like macros but we might not
+                        # have to (e.g. when the first operand of the logical
+                        # "and" is evaluated to False and the identifier belongs
+                        # to the second operand): replace the identifier with
+                        # the marker, which will not be replaced during the next
+                        # iterations
+                        identifier_repl = MacroHandler._invalid_identifier
+                        invalid_is_injected = True
                 else:
-                    # no function call
+                    # expansion of an object-like identifier
+
                     if macro is None or macro[0] is not None:
-                        # macro is not defined or
-                        # defined as function-like macro
-                        expr = expr.replace(identifier[0], "0")
+                        # the respective macro is not defined or defined as a
+                        # function-like one: the identifier evaluates to False
+                        identifier_repl = "0"
                     else:
-                        # identifier is defined as object-like macro
-                        expr = expr.replace(identifier[0], macro[1])
+                        # the respective macro is defined as an object-like one:
+                        # replace the identifier with the body (value) of the
+                        # macro
+                        identifier_repl = macro[1]
+
+                expr = expr.replace(identifier, identifier_repl)
 
             if prev_expr == expr:
                 break
-            else:
-                prev_expr = expr
+
+            prev_expr = expr
 
         expr = expr.replace("||", " or ")
         expr = expr.replace("&&", " and ")
         expr = expr.replace("!", "not ")
 
+        if invalid_is_injected:
+            # replace the invalid identifier with a valid Python name
+            expr = expr.replace(
+                MacroHandler._invalid_identifier,
+                MacroHandler._valid_python_name,
+            )
+
         try:
-            result = bool(eval(expr, {}))
+            eval_globals = {}
+            if invalid_is_injected:
+                # if the result does not depend on the values of the
+                # function-like identifiers, return it
+                eval_locals = {MacroHandler._valid_python_name: True}
+                possible_result = eval(expr, eval_globals, eval_locals)
+                eval_locals[MacroHandler._valid_python_name] = False
+                if possible_result != eval(expr, eval_globals, eval_locals):
+                    return 0
+                else:
+                    result = possible_result
+            else:
+                result = eval(expr, eval_globals)
             return 1 if result else -1
         except Exception:
             return 0