Fix handling of line numbers around finally-blocks. (#17737)

Author: markshannon

Lib/test/test_dis.py

@@ -333,6 +333,68 @@ def _fstring(a, b, c, d):
              28 RETURN_VALUE
 """ % (_fstring.__code__.co_firstlineno + 1,)
 
+def _tryfinally(a, b):
+    try:
+        return a
+    finally:
+        b()
+
+def _tryfinallyconst(b):
+    try:
+        return 1
+    finally:
+        b()
+
+dis_tryfinally = """\
+%3d           0 SETUP_FINALLY           12 (to 14)
+
+%3d           2 LOAD_FAST                0 (a)
+              4 POP_BLOCK
+
+%3d           6 LOAD_FAST                1 (b)
+              8 CALL_FUNCTION            0
+             10 POP_TOP
+
+%3d          12 RETURN_VALUE
+
+%3d     >>   14 LOAD_FAST                1 (b)
+             16 CALL_FUNCTION            0
+             18 POP_TOP
+             20 RERAISE
+             22 LOAD_CONST               0 (None)
+             24 RETURN_VALUE
+""" % (_tryfinally.__code__.co_firstlineno + 1,
+       _tryfinally.__code__.co_firstlineno + 2,
+       _tryfinally.__code__.co_firstlineno + 4,
+       _tryfinally.__code__.co_firstlineno + 2,
+       _tryfinally.__code__.co_firstlineno + 4,
+       )
+
+dis_tryfinallyconst = """\
+%3d           0 SETUP_FINALLY           12 (to 14)
+
+%3d           2 POP_BLOCK
+
+%3d           4 LOAD_FAST                0 (b)
+              6 CALL_FUNCTION            0
+              8 POP_TOP
+
+%3d          10 LOAD_CONST               1 (1)
+             12 RETURN_VALUE
+
+%3d     >>   14 LOAD_FAST                0 (b)
+             16 CALL_FUNCTION            0
+             18 POP_TOP
+             20 RERAISE
+             22 LOAD_CONST               0 (None)
+             24 RETURN_VALUE
+""" % (_tryfinallyconst.__code__.co_firstlineno + 1,
+       _tryfinallyconst.__code__.co_firstlineno + 2,
+       _tryfinallyconst.__code__.co_firstlineno + 4,
+       _tryfinallyconst.__code__.co_firstlineno + 2,
+       _tryfinallyconst.__code__.co_firstlineno + 4,
+       )
+
 def _g(x):
     yield x
 
@@ -563,6 +625,10 @@ def test_disassemble_coroutine(self):
     def test_disassemble_fstring(self):
         self.do_disassembly_test(_fstring, dis_fstring)
 
+    def test_disassemble_try_finally(self):
+        self.do_disassembly_test(_tryfinally, dis_tryfinally)
+        self.do_disassembly_test(_tryfinallyconst, dis_tryfinallyconst)
+
     def test_dis_none(self):
         try:
             del sys.last_traceback

Python/compile.c

@@ -1686,7 +1686,11 @@ compiler_unwind_fblock(struct compiler *c, struct fblockinfo *info,
                     return 0;
                 }
             }
+            /* Emit the finally block, restoring the line number when done */
+            int saved_lineno = c->u->u_lineno;
             VISIT_SEQ(c, stmt, info->fb_datum);
+            c->u->u_lineno = saved_lineno;
+            c->u->u_lineno_set = 0;
             if (preserve_tos) {
                 compiler_pop_fblock(c, POP_VALUE, NULL);
             }