gh-116767: fix crash on 'async with' with many context managers (GH-118348)

Account for `add_stopiteration_handler` pushing a block for `async with`.
To allow generator functions that previously almost hit the `CO_MAXBLOCKS`
limit by nesting non-async blocks, the limit is increased by 1.
This increase allows one more block in non-generator functions.

1 files changed, 16 insertions, 2 deletions

diff --git a/Python/compile.c b/Python/compile.c
index ca5551a..4e94f92 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -113,7 +113,8 @@ compiler IR.
 
 enum fblocktype { WHILE_LOOP, FOR_LOOP, TRY_EXCEPT, FINALLY_TRY, FINALLY_END,
                   WITH, ASYNC_WITH, HANDLER_CLEANUP, POP_VALUE, EXCEPTION_HANDLER,
-                  EXCEPTION_GROUP_HANDLER, ASYNC_COMPREHENSION_GENERATOR };
+                  EXCEPTION_GROUP_HANDLER, ASYNC_COMPREHENSION_GENERATOR,
+                  STOP_ITERATION };
 
 struct fblockinfo {
     enum fblocktype fb_type;
@@ -1503,6 +1504,7 @@ compiler_unwind_fblock(struct compiler *c, location *ploc,
         case EXCEPTION_HANDLER:
         case EXCEPTION_GROUP_HANDLER:
         case ASYNC_COMPREHENSION_GENERATOR:
+        case STOP_ITERATION:
             return SUCCESS;
 
         case FOR_LOOP:
@@ -2232,14 +2234,26 @@ compiler_function_body(struct compiler *c, stmt_ty s, int is_async, Py_ssize_t f
     c->u->u_metadata.u_argcount = asdl_seq_LEN(args->args);
     c->u->u_metadata.u_posonlyargcount = asdl_seq_LEN(args->posonlyargs);
     c->u->u_metadata.u_kwonlyargcount = asdl_seq_LEN(args->kwonlyargs);
+
+    NEW_JUMP_TARGET_LABEL(c, start);
+    USE_LABEL(c, start);
+    bool add_stopiteration_handler = c->u->u_ste->ste_coroutine || c->u->u_ste->ste_generator;
+    if (add_stopiteration_handler) {
+        /* wrap_in_stopiteration_handler will push a block, so we need to account for that */
+        RETURN_IF_ERROR(
+            compiler_push_fblock(c, NO_LOCATION, STOP_ITERATION,
+                                 start, NO_LABEL, NULL));
+    }
+
     for (Py_ssize_t i = first_instr; i < asdl_seq_LEN(body); i++) {
         VISIT_IN_SCOPE(c, stmt, (stmt_ty)asdl_seq_GET(body, i));
     }
-    if (c->u->u_ste->ste_coroutine || c->u->u_ste->ste_generator) {
+    if (add_stopiteration_handler) {
         if (wrap_in_stopiteration_handler(c) < 0) {
             compiler_exit_scope(c);
             return ERROR;
         }
+        compiler_pop_fblock(c, STOP_ITERATION, start);
     }
     PyCodeObject *co = optimize_and_assemble(c, 1);
     compiler_exit_scope(c);