[Python-checkins] [3.12] gh-105375: Improve PyErr_WarnExplicit() error handling (GH-105610) (#105659)

[erlend-aasland]

https://github.com/python/cpython/commit/db5022c16f94622285eda5f036450e34f5f415ce
commit: db5022c16f94622285eda5f036450e34f5f415ce
branch: 3.12
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: erlend-aasland <erlend.aasland at protonmail.com>
date: 2023-06-11T19:51:30Z
summary:

[3.12] gh-105375: Improve PyErr_WarnExplicit() error handling (GH-105610) (#105659)

Bail on first error to prevent exceptions from possibly being
overwritten.
(cherry picked from commit 567d6ae8e77579173510fc948ac06b2ababf3d40)

Co-authored-by: Erlend E. Aasland <erlend.aasland at protonmail.com>

files:
A Misc/NEWS.d/next/C API/2023-06-09-23-34-25.gh-issue-105375.n7amiF.rst
M Python/_warnings.c

diff --git a/Misc/NEWS.d/next/C API/2023-06-09-23-34-25.gh-issue-105375.n7amiF.rst b/Misc/NEWS.d/next/C API/2023-06-09-23-34-25.gh-issue-105375.n7amiF.rst
new file mode 100644
index 0000000000000..b9f95496f938e
--- /dev/null
+++ b/Misc/NEWS.d/next/C API/2023-06-09-23-34-25.gh-issue-105375.n7amiF.rst	
@@ -0,0 +1,2 @@
+Fix a bug in :c:func:`PyErr_WarnExplicit` where an exception could end up
+being overwritten if the API failed internally.
diff --git a/Python/_warnings.c b/Python/_warnings.c
index dec658680241e..1f91edbf5cb5d 100644
--- a/Python/_warnings.c
+++ b/Python/_warnings.c
@@ -1301,25 +1301,29 @@ PyErr_WarnExplicit(PyObject *category, const char *text,
                    const char *module_str, PyObject *registry)
 {
     PyObject *message = PyUnicode_FromString(text);
+    if (message == NULL) {
+        return -1;
+    }
     PyObject *filename = PyUnicode_DecodeFSDefault(filename_str);
+    if (filename == NULL) {
+        Py_DECREF(message);
+        return -1;
+    }
     PyObject *module = NULL;
-    int ret = -1;
-
-    if (message == NULL || filename == NULL)
-        goto exit;
     if (module_str != NULL) {
         module = PyUnicode_FromString(module_str);
-        if (module == NULL)
-            goto exit;
+        if (module == NULL) {
+            Py_DECREF(filename);
+            Py_DECREF(message);
+            return -1;
+        }
     }
 
-    ret = PyErr_WarnExplicitObject(category, message, filename, lineno,
-                                   module, registry);
-
- exit:
-    Py_XDECREF(message);
+    int ret = PyErr_WarnExplicitObject(category, message, filename, lineno,
+                                       module, registry);
     Py_XDECREF(module);
-    Py_XDECREF(filename);
+    Py_DECREF(filename);
+    Py_DECREF(message);
     return ret;
 }