[3.6] bpo-27169: The __debug__ constant is now optimized out at compile time. (GH-4880) (#4882)

This fixes also bpo-22091..
(cherry picked from commit 3325a6780c81f1ea51190370b5454879c4862a37)

1 files changed, 15 insertions, 30 deletions

diff --git a/Python/compile.c b/Python/compile.c
index 4d525a0..9984d55 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -1343,13 +1343,15 @@ is_const(expr_ty e)
     case Ellipsis_kind:
     case NameConstant_kind:
         return 1;
+    case Name_kind:
+        return _PyUnicode_EqualToASCIIString(e->v.Name.id, "__debug__");
     default:
         return 0;
     }
 }
 
 static PyObject *
-get_const_value(expr_ty e)
+get_const_value(struct compiler *c, expr_ty e)
 {
     switch (e->kind) {
     case Constant_kind:
@@ -1364,6 +1366,9 @@ get_const_value(expr_ty e)
         return Py_Ellipsis;
     case NameConstant_kind:
         return e->v.NameConstant.value;
+    case Name_kind:
+        assert(_PyUnicode_EqualToASCIIString(e->v.Name.id, "__debug__"));
+        return c->c_optimize ? Py_False : Py_True;
     default:
         assert(!is_const(e));
         return NULL;
@@ -3035,6 +3040,11 @@ compiler_nameop(struct compiler *c, identifier name, expr_context_ty ctx)
            !_PyUnicode_EqualToASCIIString(name, "True") &&
            !_PyUnicode_EqualToASCIIString(name, "False"));
 
+    if (ctx == Load && _PyUnicode_EqualToASCIIString(name, "__debug__")) {
+        ADDOP_O(c, LOAD_CONST, c->c_optimize ? Py_False : Py_True, consts);
+        return 1;
+    }
+
     op = 0;
     optype = OP_NAME;
     scope = PyST_GetScope(c->u->u_ste, mangled);
@@ -3298,7 +3308,7 @@ compiler_subdict(struct compiler *c, expr_ty e, Py_ssize_t begin, Py_ssize_t end
             return 0;
         }
         for (i = begin; i < end; i++) {
-            key = get_const_value((expr_ty)asdl_seq_GET(e->v.Dict.keys, i));
+            key = get_const_value(c, (expr_ty)asdl_seq_GET(e->v.Dict.keys, i));
             Py_INCREF(key);
             PyTuple_SET_ITEM(keys, i - begin, key);
         }
@@ -4044,35 +4054,10 @@ compiler_visit_keyword(struct compiler *c, keyword_ty k)
 static int
 expr_constant(struct compiler *c, expr_ty e)
 {
-    char *id;
-    switch (e->kind) {
-    case Ellipsis_kind:
-        return 1;
-    case Constant_kind:
-        return PyObject_IsTrue(e->v.Constant.value);
-    case Num_kind:
-        return PyObject_IsTrue(e->v.Num.n);
-    case Str_kind:
-        return PyObject_IsTrue(e->v.Str.s);
-    case Name_kind:
-        /* optimize away names that can't be reassigned */
-        id = PyUnicode_AsUTF8(e->v.Name.id);
-        if (id && strcmp(id, "__debug__") == 0)
-            return !c->c_optimize;
-        return -1;
-    case NameConstant_kind: {
-        PyObject *o = e->v.NameConstant.value;
-        if (o == Py_None)
-            return 0;
-        else if (o == Py_True)
-            return 1;
-        else if (o == Py_False)
-            return 0;
-    }
-    /* fall through */
-    default:
-        return -1;
+    if (is_const(e)) {
+        return PyObject_IsTrue(get_const_value(c, e));
     }
+    return -1;
 }