From 11956d7d720051268ff8f91ebdd01f81ba3ee69d Mon Sep 17 00:00:00 2001
From: dynapx <2310384514@qq.com>
Date: Tue, 14 Jul 2026 15:24:51 +0800
Subject: [PATCH] Fix C-API exception handling issues - Add PyErr_SetString for
 PyThread_allocate_lock failure   (ffi_init_once: lock allocation failure does
 not set exception)

- Add PyErr_NoMemory for ctypedescr_new OOM
  (new_struct_or_union_type: ctypedescr_new does not set exception on OOM)

- Fix signed char -1 false negative detection
  (convert_from_object: -1 is valid signed char value, check PyErr_Occurred)

- Preserve exceptions in _convert_to_char16_t/_convert_to_char32_t
  (avoid overwriting existing exception from _my_PyUnicode_AsSingleChar*)
---
 src/c/_cffi_backend.c | 3 ++-
 src/c/ffi_obj.c       | 5 +++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/c/_cffi_backend.c b/src/c/_cffi_backend.c
index b8b3d8ff..c6bf45cd 100644
--- a/src/c/_cffi_backend.c
+++ b/src/c/_cffi_backend.c
@@ -1762,7 +1762,7 @@ convert_from_object(char *data, CTypeDescrObject *ct, PyObject *init)
         switch (ct->ct_size) {
         case sizeof(char): {
             int res = _convert_to_char(init);
-            if (res < 0)
+            if (res < 0 && PyErr_Occurred())
                 return -1;
             data[0] = res;
             return 0;
@@ -5009,6 +5009,7 @@ static PyObject *new_struct_or_union_type(const char *name, int flag)
     int namelen = strlen(name);
     CTypeDescrObject *td = ctypedescr_new(namelen + 1);
     if (td == NULL)
+        PyErr_NoMemory();  /* ctypedescr_new does not set an exception on OOM */
         return NULL;
 
     td->ct_size = -1;
diff --git a/src/c/ffi_obj.c b/src/c/ffi_obj.c
index fbba2894..e1a1d1b8 100644
--- a/src/c/ffi_obj.c
+++ b/src/c/ffi_obj.c
@@ -1014,7 +1014,12 @@ static PyObject *ffi_init_once(FFIObject *self, PyObject *args, PyObject *kwds)
     if (tup == NULL) {
         lock = PyThread_allocate_lock();
         if (lock == NULL)
+        {
+            PyErr_SetString(PyExc_RuntimeError,
+                    "failed to allocate thread lock for init_once");
             return NULL;
+        }
+            
         x = PyCapsule_New(lock, "cffi_init_once_lock", _free_init_once_lock);
         if (x == NULL) {
             PyThread_free_lock(lock);