[Python] Only use Python Limited C API in ROOT Pythonizations library

guitargeek · guitargeek · commit 94ced7a5f9ee · 2026-04-01T21:09:06.000+02:00
This follows up on 4e0c7bf, swapping out the remaining use of CPython API functions that were not inside the limited API. In the cases where we're sill using private headers from cppyy, the parts of these headers that don't compile with the limited API are excluded via the `Py_LIMITED_API` preprocessor macro.
diff --git a/bindings/pyroot/cppyy/CPyCppyy/src/CPPInstance.h b/bindings/pyroot/cppyy/CPyCppyy/src/CPPInstance.h
@@ -10,7 +10,9 @@
 //////////////////////////////////////////////////////////////////////////////
 
 // Bindings
+#ifndef Py_LIMITED_API
 #include "CPPScope.h"
+#endif
 #include "Cppyy.h"
 #include "CallContext.h"     // for Parameter
 
@@ -116,12 +118,14 @@ inline void* CPPInstance::GetObject()
 }
 
 //----------------------------------------------------------------------------
+#ifndef Py_LIMITED_API
 inline Cppyy::TCppType_t CPPInstance::ObjectIsA(bool check_smart) const
 {
 // Retrieve the C++ type identifier (or raw type if smart).
     if (check_smart || !IsSmart()) return ((CPPClass*)Py_TYPE(this))->fCppType;
     return GetSmartIsA();
 }
+#endif
 
 
 //- object proxy type and type verification ----------------------------------
@@ -132,6 +136,7 @@ extern __declspec(dllimport) PyTypeObject CPPInstance_Type;
 extern PyTypeObject CPPInstance_Type;
 #endif
 
+#ifndef Py_LIMITED_API
 template<typename T>
 inline bool CPPInstance_Check(T* object)
 {
@@ -141,6 +146,7 @@ inline bool CPPInstance_Check(T* object)
         (Py_TYPE(object)->tp_new == CPPInstance_Type.tp_new || \
          PyObject_TypeCheck(object, &CPPInstance_Type));
 }
+#endif
 
 template<typename T>
 inline bool CPPInstance_CheckExact(T* object)
diff --git a/bindings/pyroot/cppyy/CPyCppyy/src/Dimensions.h b/bindings/pyroot/cppyy/CPyCppyy/src/Dimensions.h
@@ -1,6 +1,9 @@
 #ifndef CPYCPPYY_DIMENSIONS_H
 #define CPYCPPYY_DIMENSIONS_H
 
+// Bindings
+#include "CPyCppyy/CommonDefs.h"
+
 // Standard
 #include <algorithm>
 #include <initializer_list>
diff --git a/bindings/pyroot/cppyy/CPyCppyy/src/Utility.h b/bindings/pyroot/cppyy/CPyCppyy/src/Utility.h
@@ -46,7 +46,11 @@ inline PyObject* CT2CppName(PyObject* pytc, const char* cpd, bool allow_voidp)
     const std::string& name = CT2CppNameS(pytc, allow_voidp);
     if (!name.empty()) {
         if (name == "const char*") cpd = "";
-        return CPyCppyy_PyText_FromString((std::string{name}+cpd).c_str());
+#if PY_VERSION_HEX < 0x03000000
+        return PyString_FromString((std::string{name}+cpd).c_str());
+#else
+        return PyUnicode_FromString((std::string{name}+cpd).c_str());
+#endif
     }
     return nullptr;
 }
diff --git a/bindings/pyroot/pythonizations/CMakeLists.txt b/bindings/pyroot/pythonizations/CMakeLists.txt
@@ -31,6 +31,17 @@ set(libname ROOTPythonizations)
 
 add_library(${libname} SHARED ${cpp_sources})
 
+# Use what is in the limited API since Python 3.11, if we build with a lower
+# Python version, we don't bother using the limited API.
+if (Python3_VERSION VERSION_GREATER_EQUAL "3.11")
+  # On Windows we can't use the stable ABI yet: it requires linking against a
+  # different libpython, so as long as we don't build all translation units in
+  # the ROOT Pythonization library with the stable ABI we should not use it.
+  if(NOT MSVC)
+    target_compile_options(${libname} PRIVATE -DPy_LIMITED_API=0x030B0000)
+  endif()
+endif()
+
 # Set the suffix to '.so' and the prefix to 'lib'
 set_target_properties(${libname} PROPERTIES ${ROOT_LIBRARY_PROPERTIES_NO_VERSION})
 target_link_libraries(${libname} PUBLIC Core Tree CPyCppyy)
diff --git a/bindings/pyroot/pythonizations/src/CPPInstancePyz.cxx b/bindings/pyroot/pythonizations/src/CPPInstancePyz.cxx
@@ -9,7 +9,7 @@
  * For the list of contributors see $ROOTSYS/README/CREDITS.             *
  *************************************************************************/
 
-#include "PythonLimitedAPI.h"
+#include <Python.h>
 
 // Bindings
 #include "CPyCppyy/API.h"
diff --git a/bindings/pyroot/pythonizations/src/GenericPyz.cxx b/bindings/pyroot/pythonizations/src/GenericPyz.cxx
@@ -13,7 +13,7 @@
 
 #include "CPyCppyy/API.h"
 
-#include "../../cppyy/CPyCppyy/src/CPyCppyy.h"
+#include "../../cppyy/CPyCppyy/src/Cppyy.h"
 #include "../../cppyy/CPyCppyy/src/Utility.h"
 
 #include "PyROOTPythonize.h"
diff --git a/bindings/pyroot/pythonizations/src/IOHandler.cxx b/bindings/pyroot/pythonizations/src/IOHandler.cxx
@@ -8,7 +8,7 @@
  * For the list of contributors see $ROOTSYS/README/CREDITS.             *
  *************************************************************************/
 
-#include "PythonLimitedAPI.h"
+#include <Python.h>
 
 #include <fcntl.h>
 #ifdef _MSC_VER // Visual Studio
diff --git a/bindings/pyroot/pythonizations/src/PyROOTPythonize.h b/bindings/pyroot/pythonizations/src/PyROOTPythonize.h
@@ -12,7 +12,7 @@
 #ifndef PYROOT_PYTHONIZE_H
 #define PYROOT_PYTHONIZE_H
 
-#include "PythonLimitedAPI.h"
+#include <Python.h>
 
 namespace PyROOT {
 
diff --git a/bindings/pyroot/pythonizations/src/PythonLimitedAPI.h b/bindings/pyroot/pythonizations/src/PythonLimitedAPI.h
diff --git a/bindings/pyroot/pythonizations/src/RPyROOTApplication.cxx b/bindings/pyroot/pythonizations/src/RPyROOTApplication.cxx
@@ -10,7 +10,7 @@
  *************************************************************************/
 
 // Bindings
-#include "PythonLimitedAPI.h"
+#include <Python.h>
 #include "RPyROOTApplication.h"
 
 // ROOT
diff --git a/bindings/pyroot/pythonizations/src/TClassPyz.cxx b/bindings/pyroot/pythonizations/src/TClassPyz.cxx
@@ -12,7 +12,7 @@
 // Bindings
 #include "CPyCppyy/API.h"
 
-#include "../../cppyy/CPyCppyy/src/CPyCppyy.h"
+#include "../../cppyy/CPyCppyy/src/Cppyy.h"
 #include "../../cppyy/CPyCppyy/src/Utility.h"
 
 #include "PyROOTPythonize.h"
@@ -37,9 +37,15 @@ PyObject *TClassDynamicCastPyz(PyObject *self, PyObject *args)
       return nullptr;
 
    if (!CPyCppyy::Instance_Check(pyclass)) {
-      PyErr_Format(PyExc_TypeError,
-         "DynamicCast argument 1 must be a cppyy instance, got '%.200s'",
-         Py_TYPE(pyclass)->tp_name);
+      PyObject *type = (PyObject *)Py_TYPE(pyclass);
+      PyObject *name = PyObject_Str(type);
+      const char *nameStr = name ? PyUnicode_AsUTF8AndSize(name, nullptr) : nullptr;
+      if (nameStr) {
+         PyErr_Format(PyExc_TypeError, "DynamicCast argument 1 must be a cppyy instance, got '%s'", nameStr);
+      } else {
+         PyErr_SetString(PyExc_TypeError, "DynamicCast argument 1 must be a cppyy instance");
+      }
+      Py_DecRef(name);
       return nullptr;
    }
 
@@ -51,7 +57,7 @@ PyObject *TClassDynamicCastPyz(PyObject *self, PyObject *args)
 
    if (CPyCppyy::Instance_Check(pyobject)) {
       address = CPyCppyy::Instance_AsVoidPtr(pyobject);
-   } else if (PyInt_Check(pyobject) || PyLong_Check(pyobject)) {
+   } else if (PyLong_Check(pyobject)) {
       address = (void *)PyLong_AsLongLong(pyobject);
    } else {
       PyROOT::GetBuffer(pyobject, address);
diff --git a/bindings/pyroot/pythonizations/src/TTreePyz.cxx b/bindings/pyroot/pythonizations/src/TTreePyz.cxx
@@ -10,7 +10,13 @@
  *************************************************************************/
 
 // Bindings
-#include "../../cppyy/CPyCppyy/src/CPyCppyy.h"
+#include <Python.h>
+
+namespace CPyCppyy {
+typedef Py_ssize_t dim_t;
+} // namespace CPyCppyy
+
+#include "../../cppyy/CPyCppyy/src/Cppyy.h"
 #include "../../cppyy/CPyCppyy/src/CPPInstance.h"
 #include "../../cppyy/CPyCppyy/src/ProxyWrappers.h"
 #include "../../cppyy/CPyCppyy/src/Dimensions.h"
@@ -209,7 +215,7 @@ PyObject *PyROOT::GetBranchAttr(PyObject * /*self*/, PyObject *args)
       if (!finalTypeName.empty()) {
          PyObject *outTuple = PyTuple_New(2);
          PyTuple_SetItem(outTuple, 0, PyLong_FromLongLong((intptr_t)finalAddressVoidPtr));
-         PyTuple_SetItem(outTuple, 1, CPyCppyy_PyText_FromString((finalTypeName + "*").c_str()));
+         PyTuple_SetItem(outTuple, 1, PyUnicode_FromString((finalTypeName + "*").c_str()));
          return outTuple;
       }
    }
@@ -221,7 +227,7 @@ PyObject *PyROOT::GetBranchAttr(PyObject * /*self*/, PyObject *args)
       if (wrapper != nullptr) {
          PyObject *outTuple = PyTuple_New(2);
          PyTuple_SetItem(outTuple, 0, wrapper);
-         PyTuple_SetItem(outTuple, 1, CPyCppyy_PyText_FromString(""));
+         PyTuple_SetItem(outTuple, 1, PyUnicode_FromString(""));
          return outTuple;
       }
    }
@@ -242,7 +248,7 @@ PyObject *TryBranchLeafListOverload(int argc, PyObject *args)
    PyObject *name = nullptr, *address = nullptr, *leaflist = nullptr, *bufsize = nullptr;
 
    if (PyArg_ParseTuple(args, "OO!OO!|O!:Branch", &treeObj, &PyUnicode_Type, &name, &address, &PyUnicode_Type,
-                        &leaflist, &PyInt_Type, &bufsize)) {
+                        &leaflist, &PyLong_Type, &bufsize)) {
 
       auto tree = (TTree *)GetTClass(treeObj)->DynamicCast(TTree::Class(), CPyCppyy::Instance_AsVoidPtr(treeObj));
       if (!tree) {
@@ -267,7 +273,7 @@ PyObject *TryBranchLeafListOverload(int argc, PyObject *args)
             return nullptr;
          }
          if (argc == 5) {
-            branch = tree->Branch(nameString, buf, leaflistString, PyInt_AsLong(bufsize));
+            branch = tree->Branch(nameString, buf, leaflistString, PyLong_AsLong(bufsize));
          } else {
             branch = tree->Branch(nameString, buf, leaflistString);
          }
@@ -294,12 +300,12 @@ PyObject *TryBranchPtrToPtrOverloads(int argc, PyObject *args)
 
    auto bIsMatch = false;
    if (PyArg_ParseTuple(args, "OO!O!O|O!O!:Branch", &treeObj, &PyUnicode_Type, &name, &PyUnicode_Type, &clName,
-                        &address, &PyInt_Type, &bufsize, &PyInt_Type, &splitlevel)) {
+                        &address, &PyLong_Type, &bufsize, &PyLong_Type, &splitlevel)) {
       bIsMatch = true;
    } else {
       PyErr_Clear();
-      if (PyArg_ParseTuple(args, "OO!O|O!O!", &treeObj, &PyUnicode_Type, &name, &address, &PyInt_Type, &bufsize,
-                           &PyInt_Type, &splitlevel)) {
+      if (PyArg_ParseTuple(args, "OO!O|O!O!", &treeObj, &PyUnicode_Type, &name, &address, &PyLong_Type, &bufsize,
+                           &PyLong_Type, &splitlevel)) {
          bIsMatch = true;
       } else {
          PyErr_Clear();
@@ -349,10 +355,10 @@ PyObject *TryBranchPtrToPtrOverloads(int argc, PyObject *args)
          if (argc == 4) {
             branch = tree->Branch(nameString, klName.c_str(), buf);
          } else if (argc == 5) {
-            branch = tree->Branch(nameString, klName.c_str(), buf, PyInt_AsLong(bufsize));
+            branch = tree->Branch(nameString, klName.c_str(), buf, PyLong_AsLong(bufsize));
          } else if (argc == 6) {
-            branch = tree->Branch(nameString, klName.c_str(), buf, PyInt_AsLong(bufsize),
-                                  PyInt_AsLong(splitlevel));
+            branch = tree->Branch(nameString, klName.c_str(), buf, PyLong_AsLong(bufsize),
+                                  PyLong_AsLong(splitlevel));
          }
 
          return BindCppObject(branch, Cppyy::GetScope("TBranch"));

Original file line number	Diff line number	Diff line change
`@@ -46,7 +46,11 @@ inline PyObject* CT2CppName(PyObject* pytc, const char* cpd, bool allow_voidp)`
`46`	`46`	`const std::string& name = CT2CppNameS(pytc, allow_voidp);`
`47`	`47`	`if (!name.empty()) {`
`48`	`48`	`if (name == "const char*") cpd = "";`
`49`		`- return CPyCppyy_PyText_FromString((std::string{name}+cpd).c_str());`
	`49`	`+#if PY_VERSION_HEX < 0x03000000`
	`50`	`+ return PyString_FromString((std::string{name}+cpd).c_str());`
	`51`	`+#else`
	`52`	`+ return PyUnicode_FromString((std::string{name}+cpd).c_str());`
	`53`	`+#endif`
`50`	`54`	`}`
`51`	`55`	`return nullptr;`
`52`	`56`	`}`