Allow setting descriptor docstring on PyPy>v7.3.9 (GH-4701)

Cython/Compiler/Nodes.py

@@ -3491,7 +3491,7 @@ class DefNodeWrapper(FuncDefNode):
                     docstr.as_c_string_literal()))
 
             if entry.is_special:
-                code.putln('#if CYTHON_COMPILING_IN_CPYTHON')
+                code.putln('#if CYTHON_UPDATE_DESCRIPTOR_DOC')
                 code.putln(
                     "struct wrapperbase %s;" % entry.wrapperbase_cname)
                 code.putln('#endif')
@@ -4986,7 +4986,7 @@ class CClassDefNode(ClassDefNode):
                     preprocessor_guard = slot.preprocessor_guard_code() if slot else None
                     if preprocessor_guard:
                         code.putln(preprocessor_guard)
-                    code.putln('#if CYTHON_COMPILING_IN_CPYTHON')
+                    code.putln('#if CYTHON_UPDATE_DESCRIPTOR_DOC')
                     code.putln("{")
                     code.putln(
                         'PyObject *wrapper = PyObject_GetAttrString((PyObject *)&%s, "%s"); %s' % (

Cython/Utility/ModuleSetupCode.c

@@ -83,6 +83,9 @@
   #define CYTHON_USE_DICT_VERSIONS 0
   #undef CYTHON_USE_EXC_INFO_STACK
   #define CYTHON_USE_EXC_INFO_STACK 0
+  #ifndef CYTHON_UPDATE_DESCRIPTOR_DOC
+    #define CYTHON_UPDATE_DESCRIPTOR_DOC (PYPY_VERSION_HEX >= 0x07030900)
+  #endif
 
 #elif defined(PYSTON_VERSION)
   #define CYTHON_COMPILING_IN_PYPY 0
@@ -126,6 +129,9 @@
   #define CYTHON_USE_DICT_VERSIONS 0
   #undef CYTHON_USE_EXC_INFO_STACK
   #define CYTHON_USE_EXC_INFO_STACK 0
+  #ifndef CYTHON_UPDATE_DESCRIPTOR_DOC
+    #define CYTHON_UPDATE_DESCRIPTOR_DOC 1
+  #endif
 
 #else
   #define CYTHON_COMPILING_IN_PYPY 0
@@ -203,6 +209,9 @@
   #elif !defined(CYTHON_USE_EXC_INFO_STACK)
     #define CYTHON_USE_EXC_INFO_STACK (PY_VERSION_HEX >= 0x030700A3)
   #endif
+  #ifndef CYTHON_UPDATE_DESCRIPTOR_DOC
+    #define CYTHON_UPDATE_DESCRIPTOR_DOC 1
+  #endif
 #endif
 
 #if !defined(CYTHON_FAST_PYCCALL)