%callback and Python class access for C++ static member functions fixes

Fix access to C++ static member functions using Python class
staticmethod syntax, such as Klass.memberfunction instead of
Klass_memberfunction, when using -fastproxy and -builtin in
combination with %callback.

The docstring containing the callback pointers were not being patched
during module initialisation.

CHANGES.current

@@ -7,6 +7,12 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
 Version 4.1.0 (in progress)
 ===========================
 
+2022-01-14: wsfulton
+            [Python] Fix %callback and specifying the callback function as a
+            static member function using Python staticmethod syntax, such as
+            Klass.memberfunction instead of Klass_memberfunction when using
+            -builtin and -fastproxy.
+
 2022-01-11: wsfulton
             [Python] Accept keyword arguments accessing static member functions when
             using -builtin and kwargs feature and Python class staticmethod syntax.

Examples/test-suite/python/callback_runme.py

@@ -1,10 +1,14 @@
 import _callback
 from callback import *
 
+# callbacks are implemented by modifying docstrings, useful for debugging:
+# print("A_bar doc: {}".format(A_bar.__doc__))
+# print("A.bar doc: {}".format(A.bar.__doc__))
+
 if foo(2) != 2:
     raise RuntimeError
 
-if A_bar(2) != 4:
+if A.bar(2) != 4:
     raise RuntimeError
 
 if foobar(3, _callback.foo) != foo(3):
@@ -13,13 +17,12 @@ if foobar(3, _callback.foo) != foo(3):
 if foobar(3, foo) != foo(3):
     raise RuntimeError
 
-# Needs some more work for -builtin
-# if foobar(3, A.bar) != A.bar(3):
-#     raise RuntimeError
-
 if foobar(3, A_bar) != A_bar(3):
     raise RuntimeError
 
+if foobar(3, A.bar) != A.bar(3):
+    raise RuntimeError
+
 if foobar(3, foof) != foof(3):
     raise RuntimeError
 

Lib/python/pyinit.swg

@@ -58,15 +58,12 @@ SWIG_Python_InstallConstants(PyObject *d, swig_const_info constants[]) {
   }
 }
 
-/* -----------------------------------------------------------------------------*/
-/* Fix SwigMethods to carry the callback ptrs when needed */
-/* -----------------------------------------------------------------------------*/
+/* -----------------------------------------------------------------------------
+ * Patch %callback methods' docstrings to hold the callback ptrs
+ * -----------------------------------------------------------------------------*/
 
 SWIGINTERN void
-SWIG_Python_FixMethods(PyMethodDef *methods,
-		       swig_const_info *const_table,
-		       swig_type_info **types,
-		       swig_type_info **types_initial) {
+SWIG_Python_FixMethods(PyMethodDef *methods, const swig_const_info *const_table, swig_type_info **types, swig_type_info **types_initial) {
   size_t i;
   for (i = 0; methods[i].ml_name; ++i) {
     const char *c = methods[i].ml_doc;
@@ -74,7 +71,7 @@ SWIG_Python_FixMethods(PyMethodDef *methods,
     c = strstr(c, "swig_ptr: ");
     if (c) {
       int j;
-      swig_const_info *ci = 0;
+      const swig_const_info *ci = 0;
       const char *name = c + 10;
       for (j = 0; const_table[j].type; ++j) {
 	if (strncmp(const_table[j].name, name, 

Source/Modules/python.cxx

@@ -73,8 +73,10 @@ static int py3 = 0;
 
 /* C++ Support + Shadow Classes */
 
-static int have_constructor;
-static int have_repr;
+static int have_constructor = 0;
+static int have_repr = 0;
+static bool have_builtin_static_member_method_callback = false;
+static bool have_fast_proxy_static_member_method_callback = false;
 static String *real_classname;
 
 /* Thread Support */
@@ -815,6 +817,10 @@ public:
 
     Append(const_code, "{0, 0, 0, 0.0, 0, 0}};\n");
     Printf(f_wrappers, "%s\n", const_code);
+
+    if (have_fast_proxy_static_member_method_callback)
+      Printf(f_init, "  SWIG_Python_FixMethods(SwigMethods_proxydocs, swig_const_table, swig_types, swig_type_initial);\n\n");
+
     initialize_threads(f_init);
 
     Printf(f_init, "#if PY_VERSION_HEX >= 0x03000000\n");
@@ -2478,6 +2484,7 @@ public:
       Printf(methods, "\"swig_ptr: %s\"", Getattr(n, "feature:callback:name"));
       if (fastproxy) {
 	Printf(methods_proxydocs, "\"swig_ptr: %s\"", Getattr(n, "feature:callback:name"));
+	have_fast_proxy_static_member_method_callback = true;
       }
     } else {
       Append(methods, "NULL");
@@ -3935,6 +3942,10 @@ public:
     int funpack = fastunpack;
     static String *tp_new = NewString("PyType_GenericNew");
 
+    if (have_builtin_static_member_method_callback) {
+      Printf(f_init, "  SWIG_Python_FixMethods(SwigPyBuiltin_%s_methods, swig_const_table, swig_types, swig_type_initial);\n", mname);
+    }
+
     Printv(f_init, "  SwigPyBuiltin_SetMetaType(builtin_pytype, metatype);\n", NIL);
 
     // We can’t statically initialize a structure member with a function defined in another C module
@@ -4365,6 +4376,7 @@ public:
       /* Create new strings for building up a wrapper function */
       have_constructor = 0;
       have_repr = 0;
+      have_builtin_static_member_method_callback = false;
 
       class_name = Getattr(n, "sym:name");
       real_classname = Getattr(n, "name");
@@ -4750,6 +4762,11 @@ public:
 	  String *ds = cdocstring(n, AUTODOC_STATICFUNC);
 	  Printf(builtin_methods, "  { \"%s\", (PyCFunction)(void(*)(void))%s, %s, \"%s\" },\n", symname, wname, pyflags, ds);
 	  Delete(ds);
+	} else if (Getattr(n, "feature:callback")) {
+	  String *ds = NewStringf("swig_ptr: %s", Getattr(n, "feature:callback:name"));
+	  Printf(builtin_methods, "  { \"%s\", (PyCFunction)(void(*)(void))%s, %s, \"%s\" },\n", symname, wname, pyflags, ds);
+	  Delete(ds);
+	  have_builtin_static_member_method_callback = true;
 	} else {
 	  Printf(builtin_methods, "  { \"%s\", (PyCFunction)(void(*)(void))%s, %s, \"\" },\n", symname, wname, pyflags);
 	}