From 166f4591d216af0a86b73f3841231975e5625389 Mon Sep 17 00:00:00 2001
From: Anshu <anshubaka2004@gmail.com>
Date: Wed, 26 Nov 2025 14:48:42 +0530
Subject: [PATCH] Merge pull request #28047 from
 0AnshuAditya0:fix-pyos-fspath-memory-leak
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Fix memory leak in pyopencv_to for path-like objects #28047

This PR fixes a memory leak in pyopencv_to when handling path-like objects (e.g., pathlib.Path).
Problem:
PyOS_FSPath() returns a new strong reference, but the code was not calling Py_XDECREF to decrement it, causing a memory leak on every call with path-like arguments.
Solution:

Store the returned reference from PyOS_FSPath() in a separate variable path_obj
Call Py_XDECREF(path_obj) on all function exit paths (both success and error paths)
This ensures proper reference counting without changing the function's behavior

Testing:
The leak can be reproduced using the steps in issue #28046 with Python built with --with-address-sanitizer. This fix ensures the reference is properly released.
Fixes #28046

Pull Request Readiness Checklist
See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

 ✓ I agree to contribute to the project under Apache 2 License.
 ✓ To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
 ✓ The PR is proposed to the proper branch (4.x)
 ✓ There is a reference to the original bug report and related work (#28046)
 NA There is accuracy test, performance test and test data in opencv_extra repository, if applicable
Patch to opencv_extra has the same branch name.
 ✓ The feature is well documented and sample code can be built with the project CMake
---
 modules/python/src2/cv2_convert.cpp | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/modules/python/src2/cv2_convert.cpp b/modules/python/src2/cv2_convert.cpp
index 577c079dcd..1161995495 100644
--- a/modules/python/src2/cv2_convert.cpp
+++ b/modules/python/src2/cv2_convert.cpp
@@ -711,28 +711,29 @@ bool pyopencv_to(PyObject* obj, String &value, const ArgInfo& info)
     std::string str;
 
 #if ((PY_VERSION_HEX >= 0x03060000) && !defined(Py_LIMITED_API)) || (Py_LIMITED_API >= 0x03060000)
+    PyObject* path_obj = NULL;
     if (info.pathlike)
     {
-        obj = PyOS_FSPath(obj);
+        path_obj = PyOS_FSPath(obj);
         if (PyErr_Occurred())
         {
             failmsg("Expected '%s' to be a str or path-like object", info.name);
             return false;
         }
+        obj = path_obj;
     }
 #endif
+
+    bool result = false;
     if (getUnicodeString(obj, str))
     {
         value = str;
-        return true;
+        result = true;
     }
     else
     {
-        // If error hasn't been already set by Python conversion functions
         if (!PyErr_Occurred())
         {
-            // Direct access to underlying slots of PyObjectType is not allowed
-            // when limited API is enabled
 #ifdef Py_LIMITED_API
             failmsg("Can't convert object to 'str' for '%s'", info.name);
 #else
@@ -741,7 +742,12 @@ bool pyopencv_to(PyObject* obj, String &value, const ArgInfo& info)
 #endif
         }
     }
-    return false;
+
+#if ((PY_VERSION_HEX >= 0x03060000) && !defined(Py_LIMITED_API)) || (Py_LIMITED_API >= 0x03060000)
+    Py_XDECREF(path_obj);
+#endif
+
+    return result;
 }
 
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