From 9b1d670361215f8d56de7a05cb1d430009735fd5 Mon Sep 17 00:00:00 2001
From: Dirkjan Ochtman <dirkjan@ochtman.nl>
Date: Tue, 29 Jul 2014 17:21:39 +0200
Subject: [PATCH] Issue #21591: Handle exec backwards compatibility in the AST
 builder.

Instead of deferring until runtime. This makes sure we hit the right
conditions in dealing with unqualified exec statements.

Reviewed by Victor Stinner. Test follows in a later commit.
---
 Misc/NEWS      |  3 +++
 Python/ast.c   | 12 ++++++++++++
 Python/ceval.c |  9 ---------
 3 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/Misc/NEWS b/Misc/NEWS
index bdd414ebeb..f6dda99278 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,9 @@ What's New in Python 2.7.9?
 Core and Builtins
 -----------------
 
+- Issue #21591: Correctly handle qualified exec statements in tuple form by
+  moving compatibility layer from run-time to AST transformation.
+
 Library
 -------
 
diff --git a/Python/ast.c b/Python/ast.c
index 80e6354ed4..ffd5679e09 100644
--- a/Python/ast.c
+++ b/Python/ast.c
@@ -2679,6 +2679,18 @@ ast_for_exec_stmt(struct compiling *c, const node *n)
     expr1 = ast_for_expr(c, CHILD(n, 1));
     if (!expr1)
         return NULL;
+
+    if (expr1->kind == Tuple_kind && n_children < 4 &&
+        (asdl_seq_LEN(expr1->v.Tuple.elts) == 2 ||
+         asdl_seq_LEN(expr1->v.Tuple.elts) == 3)) {
+        /* Backwards compatibility: pass exec args as a tuple */
+        globals = (expr_ty) asdl_seq_GET(expr1->v.Tuple.elts, 1);
+        if (asdl_seq_LEN(expr1->v.Tuple.elts) == 3) {
+            locals = (expr_ty) asdl_seq_GET(expr1->v.Tuple.elts, 2);
+        }
+        expr1 = (expr_ty) asdl_seq_GET(expr1->v.Tuple.elts, 0);
+    }
+
     if (n_children >= 4) {
         globals = ast_for_expr(c, CHILD(n, 3));
         if (!globals)
diff --git a/Python/ceval.c b/Python/ceval.c
index e00860831f..38f51faf69 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -4673,18 +4673,9 @@ static int
 exec_statement(PyFrameObject *f, PyObject *prog, PyObject *globals,
                PyObject *locals)
 {
-    int n;
     PyObject *v;
     int plain = 0;
 
-    if (PyTuple_Check(prog) && globals == Py_None && locals == Py_None &&
-        ((n = PyTuple_Size(prog)) == 2 || n == 3)) {
-        /* Backward compatibility hack */
-        globals = PyTuple_GetItem(prog, 1);
-        if (n == 3)
-            locals = PyTuple_GetItem(prog, 2);
-        prog = PyTuple_GetItem(prog, 0);
-    }
     if (globals == Py_None) {
         globals = PyEval_GetGlobals();
         if (locals == Py_None) {
-- 
2.50.1