[3.11] gh-101517: fix line number propagation in code generated for except* (#103550) (#103816)

Manual backport of #103550.



<!-- gh-issue-number: gh-101517 -->
* Issue: gh-101517
<!-- /gh-issue-number -->

---------

Co-authored-by: Łukasz Langa <[email protected]>

Author: iritkatriel

Lib/bdb.py

@@ -574,6 +574,8 @@ def format_stack_entry(self, frame_lineno, lprefix=': '):
             line = linecache.getline(filename, lineno, frame.f_globals)
             if line:
                 s += lprefix + line.strip()
+        else:
+            s += f'{lprefix}Warning: lineno is None'
         return s
 
     # The following methods can be called by clients to use

Lib/test/test_bdb.py

@@ -1206,7 +1206,8 @@ def main():
 class TestRegressions(unittest.TestCase):
     def test_format_stack_entry_no_lineno(self):
         # See gh-101517
-        Bdb().format_stack_entry((sys._getframe(), None))
+        self.assertIn('Warning: lineno is None',
+                      Bdb().format_stack_entry((sys._getframe(), None)))
 
 
 if __name__ == "__main__":

Lib/test/test_pdb.py

@@ -1653,6 +1653,25 @@ def test_pdb_issue_gh_101673():
     (Pdb) continue
     """
 
+def test_pdb_issue_gh_101517():
+    """See GH-101517
+
+    Make sure pdb doesn't crash when the exception is caught in a try/except* block
+
+    >>> def test_function():
+    ...     try:
+    ...         raise KeyError
+    ...     except* Exception as e:
+    ...         import pdb; pdb.Pdb(nosigint=True, readrc=False).set_trace()
+
+    >>> with PdbTestInput([  # doctest: +NORMALIZE_WHITESPACE
+    ...     'continue'
+    ... ]):
+    ...    test_function()
+    > <doctest test.test_pdb.test_pdb_issue_gh_101517[0]>(4)test_function()
+    -> except* Exception as e:
+    (Pdb) continue
+    """
 
 @support.requires_subprocess()
 class PdbTestCase(unittest.TestCase):

Misc/NEWS.d/next/Core and Builtins/2023-04-14-22-35-23.gh-issue-101517.5EqM-S.rst

@@ -0,0 +1 @@
+Fix bug in line numbers of instructions emitted for :keyword:`except* <except_star>`.

Python/compile.c

@@ -3613,21 +3613,25 @@ compiler_try_except(struct compiler *c, stmt_ty s)
 
    [orig, res, exc]                           <evaluate E1>
    [orig, res, exc, E1]                       CHECK_EG_MATCH
-   [orig, red, rest/exc, match?]              COPY 1
-   [orig, red, rest/exc, match?, match?]      POP_JUMP_IF_NOT_NONE  H1
-   [orig, red, exc, None]                     POP_TOP
-   [orig, red, exc]                           JUMP L2
+   [orig, res, rest/exc, match?]              COPY 1
+   [orig, res, rest/exc, match?, match?]      POP_JUMP_IF_NONE      C1
 
-   [orig, res, rest, match]         H1:       <assign to V1>  (or POP if no V1)
+   [orig, res, rest, match]                   <assign to V1>  (or POP if no V1)
 
    [orig, res, rest]                          SETUP_FINALLY         R1
    [orig, res, rest]                          <code for S1>
    [orig, res, rest]                          JUMP                  L2
 
    [orig, res, rest, i, v]          R1:       LIST_APPEND   3 ) exc raised in except* body - add to res
    [orig, res, rest, i]                       POP
+   [orig, res, rest]                          JUMP                  LE2
 
-   [orig, res, rest]                L2:       <evaluate E2>
+   [orig, res, rest]                L2:       NOP  ) for lineno
+   [orig, res, rest]                          JUMP                  LE2
+
+   [orig, res, rest/exc, None]      C1:       POP
+
+   [orig, res, rest]               LE2:       <evaluate E2>
    .............................etc.......................
 
    [orig, res, rest]                Ln+1:     LIST_APPEND 1  ) add unhandled exc to res (could be None)
@@ -3700,8 +3704,12 @@ compiler_try_star_except(struct compiler *c, stmt_ty s)
         if (except == NULL) {
             return 0;
         }
-        basicblock *handle_match = compiler_new_block(c);
-        if (handle_match == NULL) {
+        basicblock *except_with_error = compiler_new_block(c);
+        if (except_with_error == NULL) {
+            return 0;
+        }
+        basicblock *no_match = compiler_new_block(c);
+        if (no_match == NULL) {
             return 0;
         }
         if (i == 0) {
@@ -3725,13 +3733,9 @@ compiler_try_star_except(struct compiler *c, stmt_ty s)
             VISIT(c, expr, handler->v.ExceptHandler.type);
             ADDOP(c, CHECK_EG_MATCH);
             ADDOP_I(c, COPY, 1);
-            ADDOP_JUMP(c, POP_JUMP_IF_NOT_NONE, handle_match);
-            ADDOP(c, POP_TOP);  // match
-            ADDOP_JUMP(c, JUMP, except);
+            ADDOP_JUMP(c, POP_JUMP_IF_NONE, no_match);
         }
 
-        compiler_use_next_block(c, handle_match);
-
         basicblock *cleanup_end = compiler_new_block(c);
         if (cleanup_end == NULL) {
             return 0;
@@ -3793,8 +3797,14 @@ compiler_try_star_except(struct compiler *c, stmt_ty s)
         ADDOP_I(c, LIST_APPEND, 3); // exc
         ADDOP(c, POP_TOP); // lasti
 
-        ADDOP_JUMP(c, JUMP, except);
+        ADDOP_JUMP(c, JUMP, except_with_error);
         compiler_use_next_block(c, except);
+        ADDOP(c, NOP);  // to hold a propagated location info
+        ADDOP_JUMP(c, JUMP, except_with_error);
+        compiler_use_next_block(c, no_match);
+        ADDOP(c, POP_TOP);  // match (None)
+
+        compiler_use_next_block(c, except_with_error);
 
         if (i == n - 1) {
             /* Add exc to the list (if not None it's the unhandled part of the EG) */