From d651ff8d6b9669b8214876568694c1dca7c2ef8a Mon Sep 17 00:00:00 2001
From: Alexander Alekhin <alexander.a.alekhin@gmail.com>
Date: Wed, 31 Mar 2021 14:17:45 +0000
Subject: [PATCH] python: exception-free pyopencv_to() wrapper

---
 modules/python/src2/cv2.cpp | 28 ++++++++++++++++++++++++++--
 modules/python/src2/gen2.py | 12 ++++++------
 2 files changed, 32 insertions(+), 8 deletions(-)

diff --git a/modules/python/src2/cv2.cpp b/modules/python/src2/cv2.cpp
index 8bb15cd43f..0806e03552 100644
--- a/modules/python/src2/cv2.cpp
+++ b/modules/python/src2/cv2.cpp
@@ -44,6 +44,7 @@
 
 #define CV_HAS_CONVERSION_ERROR(x) (((x) == -1) && PyErr_Occurred())
 
+static PyObject* opencv_error = NULL;
 
 class ArgInfo
 {
@@ -66,14 +67,32 @@ struct PyOpenCV_Converter
     //static inline PyObject* from(const T& src);
 };
 
+// exception-safe pyopencv_to
+template<typename _Tp> static
+bool pyopencv_to_safe(PyObject* obj, _Tp& value, const ArgInfo& info)
+{
+    try
+    {
+        return pyopencv_to(obj, value, info);
+    }
+    catch (const std::exception &e)
+    {
+        PyErr_SetString(opencv_error, cv::format("Conversion error: %s, what: %s", info.name, e.what()).c_str());
+        return false;
+    }
+    catch (...)
+    {
+        PyErr_SetString(opencv_error, cv::format("Conversion error: %s", info.name).c_str());
+        return false;
+    }
+}
+
 template<typename T> static
 bool pyopencv_to(PyObject* obj, T& p, const ArgInfo& info) { return PyOpenCV_Converter<T>::to(obj, p, info); }
 
 template<typename T> static
 PyObject* pyopencv_from(const T& src) { return PyOpenCV_Converter<T>::from(src); }
 
-static PyObject* opencv_error = NULL;
-
 static bool isPythonBindingsDebugEnabled()
 {
     static bool param_debug = cv::utils::getConfigurationParameterBool("OPENCV_PYTHON_DEBUG", false);
@@ -211,6 +230,11 @@ catch (const std::exception &e) \
 { \
     PyErr_SetString(opencv_error, e.what()); \
     return 0; \
+} \
+catch (...) \
+{ \
+    PyErr_SetString(opencv_error, "Unknown C++ exception from OpenCV code"); \
+    return 0; \
 }
 
 using namespace cv;
diff --git a/modules/python/src2/gen2.py b/modules/python/src2/gen2.py
index 4acca07ada..b25647c4b3 100755
--- a/modules/python/src2/gen2.py
+++ b/modules/python/src2/gen2.py
@@ -47,7 +47,7 @@ gen_template_func_body = Template("""$code_decl
 gen_template_mappable = Template("""
     {
         ${mappable} _src;
-        if (pyopencv_to(src, _src, info))
+        if (pyopencv_to_safe(src, _src, info))
         {
             return cv_mappable_to(_src, dst);
         }
@@ -91,7 +91,7 @@ gen_template_set_prop_from_map = Template("""
     if( PyMapping_HasKeyString(src, (char*)"$propname") )
     {
         tmp = PyMapping_GetItemString(src, (char*)"$propname");
-        ok = tmp && pyopencv_to(tmp, dst.$propname, ArgInfo("$propname", false));
+        ok = tmp && pyopencv_to_safe(tmp, dst.$propname, ArgInfo("$propname", false));
         Py_DECREF(tmp);
         if(!ok) return false;
     }""")
@@ -145,7 +145,7 @@ static int pyopencv_${name}_set_${member}(pyopencv_${name}_t* p, PyObject *value
         PyErr_SetString(PyExc_TypeError, "Cannot delete the ${member} attribute");
         return -1;
     }
-    return pyopencv_to(value, p->v${access}${member}, ArgInfo("value", false)) ? 0 : -1;
+    return pyopencv_to_safe(value, p->v${access}${member}, ArgInfo("value", false)) ? 0 : -1;
 }
 """)
 
@@ -163,7 +163,7 @@ static int pyopencv_${name}_set_${member}(pyopencv_${name}_t* p, PyObject *value
         failmsgp("Incorrect type of object (must be '${name}' or its derivative)");
         return -1;
     }
-    return pyopencv_to(value, _self_${access}${member}, ArgInfo("value", false)) ? 0 : -1;
+    return pyopencv_to_safe(value, _self_${access}${member}, ArgInfo("value", false)) ? 0 : -1;
 }
 """)
 
@@ -281,7 +281,7 @@ class ClassInfo(object):
         code = "static bool pyopencv_to(PyObject* src, %s& dst, const ArgInfo& info)\n{\n    PyObject* tmp;\n    bool ok;\n" % (self.cname)
         code += "".join([gen_template_set_prop_from_map.substitute(propname=p.name,proptype=p.tp) for p in self.props])
         if self.base:
-            code += "\n    return pyopencv_to(src, (%s&)dst, info);\n}\n" % all_classes[self.base].cname
+            code += "\n    return pyopencv_to_safe(src, (%s&)dst, info);\n}\n" % all_classes[self.base].cname
         else:
             code += "\n    return true;\n}\n"
         return code
@@ -665,7 +665,7 @@ class FuncInfo(object):
                         if a.tp == 'char':
                             code_cvt_list.append("convert_to_char(pyobj_%s, &%s, %s)" % (a.name, a.name, a.crepr()))
                         else:
-                            code_cvt_list.append("pyopencv_to(pyobj_%s, %s, %s)" % (a.name, a.name, a.crepr()))
+                            code_cvt_list.append("pyopencv_to_safe(pyobj_%s, %s, %s)" % (a.name, a.name, a.crepr()))
 
                 all_cargs.append([arg_type_info, parse_name])