cpp: defend against recursion in computing decltypes

MiguelMarcelino · Jun 26, 2021 · 967d9fe · 967d9fe
1 parent c46f5c4
commit 967d9fe
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Showing 3 changed files with 36 additions and 14 deletions.
diff --git a/py2many/tracer.py b/py2many/tracer.py
@@ -91,28 +91,47 @@ def value_type(node):
 
 
 class ValueExpressionVisitor(ast.NodeVisitor):
+    def __init__(self):
+        super().__init__()
+        self._stack = []
+
     def visit_Constant(self, node):
         return str(node.n)
 
     def visit_Str(self, node):
         return node.s
 
     def visit_Name(self, node):
-        var = node.scopes.find(get_id(node))
+        name = get_id(node)
+        if name in self._stack:
+            # Avoid infinite recursion in cases like foo = bar(foo)
+            return name
+        self._stack.append(name)
+        try:
+            return self._visit_Name(node)
+        finally:
+            self._stack.pop()
+
+    def _visit_Name(self, node):
+        name = get_id(node)
+        var = node.scopes.find(name)
 
         if not var:  # TODO why no scopes found for node id?
-            return get_id(node)
+            return name
 
         # TODO: code looks C++ specific. Move out
-        if isinstance(var.assigned_from, ast.For):
-            it = var.assigned_from.iter
-            return "std::declval<typename decltype({0})::value_type>()".format(
-                self.visit(it)
-            )
-        elif isinstance(var.assigned_from, ast.FunctionDef):
-            return get_id(var)
+        if hasattr(var, "assigned_from"):
+            if isinstance(var.assigned_from, ast.For):
+                it = var.assigned_from.iter
+                return "std::declval<typename decltype({0})::value_type>()".format(
+                    self.visit(it)
+                )
+            elif isinstance(var.assigned_from, ast.FunctionDef):
+                return get_id(var)
+            else:
+                return self.visit(var.assigned_from.value)
         else:
-            return self.visit(var.assigned_from.value)
+            return name
 
     def visit_Call(self, node):
         arg_strings = [self.visit(arg) for arg in node.args]
@@ -132,6 +151,9 @@ def visit_BinOp(self, node):
 
 
 class ValueTypeVisitor(ast.NodeVisitor):
+    def generic_visit(self, node):
+        return "auto"
+
     def visit_Constant(self, node):
         return value_expr(node)
 

diff --git a/pycpp/transpiler.py b/pycpp/transpiler.py
@@ -511,7 +511,7 @@ def visit_List(self, node):
         if element_type == self._default_type:
             typename = decltype(node)
             # Workaround for cases where we couldn't figure out type
-            if "(None)" in typename:
+            if "auto" in typename:
                 return f"{{{elements_str}}}"
             return f"{typename}{{{elements_str}}}"
         return f"std::vector<{element_type}>{{{elements_str}}}"

diff --git a/tests/test_transpile_self.py b/tests/test_transpile_self.py
@@ -194,14 +194,14 @@ def test_cpp_recursive(self):
         assert len(successful) == 10
         assert set(failures) == {
             transpiler_module / "plugins.py",
-            transpiler_module / "transpiler.py",
+            transpiler_module / "__init__.py",
         }
 
         successful, format_errors, failures = _process_dir(
             settings, PY2MANY_MODULE, OUT_DIR, _suppress_exceptions=suppress_exceptions
         )
-        assert len(successful) == 13
-        assert len(failures) == 3
+        assert len(successful) == 16
+        assert len(failures) == 1
 
     def test_julia_recursive(self):
         settings = self.SETTINGS["julia"]