gdb/python: fix memory leak in gdb_py_tp_name

The current implementation of gdb_py_tp_name() leaks a reference to the
object returned by PyType_GetFullyQualifiedName() for Python >= 3.13, and
PyType_GetQualName() for Python >= 3.11.

Managing the strong reference on the returned PyObject* with a gdbpy_ref<>
fixes the reference count, but also causes the temporary object to be
deallocated on function exit. As a consequence, the 'const char *' returned
by PyUnicode_AsUTF8AndSize() becomes dangling and can no longer safely be
returned.

The proposed approach consists in changing gdb_py_tp_name() to return a
std::string, and forcing a copy of the 'const char *' value, statically
or dynamically allocated, stored in a temporary or non-temporary PyObject,
depending on the version of Python it was compiled with.
An unfortunate side effect of this fix is that every call sites where the
tp_name is printed, must now use `.c_str()' because PyErr_Format()
and its siblings cannot handle std::string.

Approved-By: Andrew Burgess <aburgess@redhat.com>

gdb/python/py-arch.c

@@ -343,7 +343,7 @@ archpy_repr (PyObject *self)
 
   auto arch_info = gdbarch_bfd_arch_info (gdbarch);
   return PyUnicode_FromFormat ("<%s arch_name=%s printable_name=%s>",
-			       gdbpy_py_obj_tp_name (self),
+			       gdbpy_py_obj_tp_name (self).c_str (),
 			       arch_info->arch_name,
 			       arch_info->printable_name);
 }

gdb/python/py-block.c

@@ -527,7 +527,7 @@ blpy_repr (PyObject *self)
 	str += ", ";
     }
   return PyUnicode_FromFormat ("<%s %s {%s}>",
-			       gdbpy_py_obj_tp_name (self),
+			       gdbpy_py_obj_tp_name (self).c_str (),
 			       name, str.c_str ());
 }
 

gdb/python/py-breakpoint.c

@@ -1067,7 +1067,7 @@ bppy_init (PyObject *self, PyObject *args, PyObject *kwargs)
 static PyObject *
 bppy_repr (PyObject *self)
 {
-  const char *tp_name = gdbpy_py_obj_tp_name (self);
+  const auto &tp_name = gdbpy_py_obj_tp_name (self);
 
   const auto bp = (struct gdbpy_breakpoint_object*) self;
   if (bp->bp == nullptr)
@@ -1083,7 +1083,7 @@ bppy_repr (PyObject *self)
   str.pop_back ();
 
   return PyUnicode_FromFormat ("<%s%s number=%d hits=%d%s>",
-			       tp_name,
+			       tp_name.c_str (),
 			       (bp->bp->enable_state == bp_enabled
 				? "" : " disabled"), bp->bp->number,
 			       bp->bp->hit_count, str.c_str ());
@@ -1776,7 +1776,7 @@ bplocpy_repr (PyObject *py_self)
     }
 
   return PyUnicode_FromFormat ("<%s %s>",
-			       gdbpy_py_obj_tp_name (py_self),
+			       gdbpy_py_obj_tp_name (py_self).c_str (),
 			       str.c_str ());
 }
 

gdb/python/py-connection.c

@@ -203,7 +203,7 @@ connpy_repr (PyObject *obj)
     return gdb_py_invalid_object_repr (obj);
 
   return PyUnicode_FromFormat ("<%s num=%d, what=\"%s\">",
-			       gdbpy_py_obj_tp_name (obj),
+			       gdbpy_py_obj_tp_name (obj).c_str (),
 			       target->connection_number,
 			       make_target_connection_string (target).c_str ());
 }

gdb/python/py-corefile.c

@@ -400,7 +400,7 @@ cfpy_repr (PyObject *self)
   bfd *core_bfd = get_inferior_core_bfd (obj->inferior);
   gdb_assert (core_bfd != nullptr);
   return PyUnicode_FromFormat ("<%s inferior=%d filename='%s'>",
-			       gdbpy_py_obj_tp_name (self),
+			       gdbpy_py_obj_tp_name (self).c_str (),
 			       obj->inferior->num,
 			       bfd_get_filename (core_bfd));
 }

gdb/python/py-disasm.c

@@ -312,7 +312,7 @@ disasmpy_info_repr (PyObject *self)
   const char *arch_name
     = (gdbarch_bfd_arch_info (obj->gdbarch))->printable_name;
   return PyUnicode_FromFormat ("<%s address=%s architecture=%s>",
-			       gdbpy_py_obj_tp_name (self),
+			       gdbpy_py_obj_tp_name (self).c_str (),
 			       core_addr_to_string_nz (obj->address),
 			       arch_name);
 }
@@ -1003,7 +1003,7 @@ disasmpy_result_init (PyObject *self, PyObject *args, PyObject *kwargs)
     {
       PyErr_Format (PyExc_ValueError,
 		    _("Cannot use 'string' and 'parts' when creating %s."),
-		    gdbpy_py_obj_tp_name (self));
+		    gdbpy_py_obj_tp_name (self).c_str ());
       return -1;
     }
 
@@ -1087,7 +1087,7 @@ disasmpy_result_repr (PyObject *self)
   gdb_assert (obj->parts != nullptr);
 
   return PyUnicode_FromFormat ("<%s length=%d string=\"%U\">",
-			       gdbpy_py_obj_tp_name (self),
+			       gdbpy_py_obj_tp_name (self).c_str (),
 			       obj->length,
 			       disasmpy_result_str (self));
 }
@@ -1302,7 +1302,7 @@ gdbpy_print_insn (struct gdbarch *gdbarch, CORE_ADDR memaddr,
       PyErr_Format
 	(PyExc_TypeError,
 	 _("Result from Disassembler must be gdb.DisassemblerResult, not %s."),
-	 gdbpy_py_obj_tp_name (result.get ()));
+	 gdbpy_py_obj_tp_name (result.get ()).c_str ());
       gdbpy_print_stack ();
       return std::optional<int> (-1);
     }
@@ -1391,7 +1391,7 @@ disasmpy_part_init (PyObject *self, PyObject *args, PyObject *kwargs)
 {
   PyErr_Format (PyExc_RuntimeError,
 		_("Cannot create instances of %s."),
-		gdbpy_py_obj_tp_name (self));
+		gdbpy_py_obj_tp_name (self).c_str ());
   return -1;
 }
 
@@ -1428,7 +1428,7 @@ disasmpy_text_part_repr (PyObject *self)
   gdb_assert (obj->string != nullptr);
 
   return PyUnicode_FromFormat ("<%s string='%s', style='%s'>",
-			       gdbpy_py_obj_tp_name (self),
+			       gdbpy_py_obj_tp_name (self).c_str (),
 			       obj->string->c_str (),
 			       get_style_name (obj->style));
 }
@@ -1471,7 +1471,7 @@ disasmpy_addr_part_repr (PyObject *self)
   disasm_addr_part_object *obj = (disasm_addr_part_object *) self;
 
   return PyUnicode_FromFormat ("<%s address='%s'>",
-			       gdbpy_py_obj_tp_name (self),
+			       gdbpy_py_obj_tp_name (self).c_str (),
 			       core_addr_to_string_nz (obj->address));
 }
 

gdb/python/py-frame.c

@@ -97,7 +97,7 @@ frapy_repr (PyObject *self)
 
   const frame_id &fid = frame_obj->frame_id;
   return PyUnicode_FromFormat ("<%s level=%d frame-id=%s>",
-			       gdbpy_py_obj_tp_name (self),
+			       gdbpy_py_obj_tp_name (self).c_str (),
 			       frame_relative_level (f_info),
 			       fid.to_string ().c_str ());
 }
@@ -545,7 +545,7 @@ frapy_read_var (PyObject *self, PyObject *args, PyObject *kw)
     {
       PyErr_Format (PyExc_TypeError,
 		    _("argument 1 must be gdb.Symbol or str, not %s"),
-		    gdbpy_py_obj_tp_name (sym_obj));
+		    gdbpy_py_obj_tp_name (sym_obj).c_str ());
       return NULL;
     }
 

gdb/python/py-infthread.c

@@ -354,7 +354,7 @@ thpy_repr (PyObject *self)
 
   thread_info *thr = thread_obj->thread;
   return PyUnicode_FromFormat ("<%s id=%s target-id=\"%s\">",
-			       gdbpy_py_obj_tp_name (self),
+			       gdbpy_py_obj_tp_name (self).c_str (),
 			       print_full_thread_id (thr),
 			       target_pid_to_str (thr->ptid).c_str ());
 }

gdb/python/py-mi.c

@@ -379,7 +379,7 @@ gdbpy_notify_mi (PyObject *self, PyObject *args, PyObject *kwargs)
       PyErr_Format
 	(PyExc_ValueError,
 	 _("MI notification data must be either None or a dictionary, not %s"),
-	 gdbpy_py_obj_tp_name (data));
+	 gdbpy_py_obj_tp_name (data).c_str ());
       return nullptr;
     }
 

gdb/python/py-micmd.c

@@ -511,7 +511,9 @@ micmdpy_set_installed (PyObject *self, PyObject *newvalue, void *closure)
     {
       PyErr_Format (PyExc_TypeError,
 		    _("gdb.MICommand.installed must be set to a bool, not %s"),
-		    newvalue == Py_None ? "None" : gdbpy_py_obj_tp_name (newvalue));
+		    (newvalue == Py_None
+		     ? "None"
+		     : gdbpy_py_obj_tp_name (newvalue).c_str ()));
       return -1;
     }
 

gdb/python/py-obj-type.c

@@ -21,20 +21,44 @@
 #include "py-obj-type.h"
 
 /* Return the type's fully qualified name from a PyTypeObject.  */
-const char *
+std::string
 gdb_py_tp_name (PyTypeObject *py_type) noexcept
 {
-#if PY_VERSION_HEX >= 0x030d0000
-  /* Note: PyType_GetFullyQualifiedName() was added in version 3.13, and is
-     part of the stable ABI since version 3.13.  */
-  PyObject *fully_qualified_name = PyType_GetFullyQualifiedName (py_type);
-  if (fully_qualified_name == nullptr)
-    return nullptr;
+  static const std::string NO_TYPE_NAME = "<type name unavailable>";
 
-  return PyUnicode_AsUTF8AndSize (fully_qualified_name, nullptr);
+  /* This helper should be used for cases when the called CPython function
+     informs the caller that an error occurred, and a Python error was set.  */
+  auto handle_err = [&]() -> std::string
+  {
+    gdbpy_print_stack ();
+    PyErr_Clear ();
+    return NO_TYPE_NAME;
+  };
+
+  /* Convert a PyObject to a UTF-8 encoded string.  */
+  auto pyobj_to_str = [&](PyObject *name) -> std::string
+  {
+    const char *s = PyUnicode_AsUTF8AndSize (name, nullptr);
+    if (s == nullptr)
+      return handle_err ();
+    return s;
+  };
+
+#if PY_VERSION_HEX >= 0x030d0000
+  /* Notes:
+     1. PyType_GetFullyQualifiedName() was added in version 3.13, and is
+	part of the stable ABI since version 3.13.
+     2. If an error occurs when looking up the module name (for instance,
+	during the destruction of the object), PyType_GetFullyQualifiedName()
+	returns NULL, and a Python error is set.  */
+  gdbpy_ref<> fully_qualified_name (PyType_GetFullyQualifiedName (py_type));
+  if (fully_qualified_name == nullptr)
+    return handle_err ();
+  return pyobj_to_str (fully_qualified_name.get ());
 
 #else /* PY_VERSION_HEX < 0x030d0000 && ! defined (Py_LIMITED_API)  */
-  /* For non-heap types, the fully qualified name corresponds to tp_name.  */
+  /* For non-heap types, the fully qualified name corresponds to tp_name,
+     which can never be NULL.  */
   if (! (PyType_GetFlags (py_type) & Py_TPFLAGS_HEAPTYPE))
     return py_type->tp_name;
 
@@ -43,12 +67,17 @@ gdb_py_tp_name (PyTypeObject *py_type) noexcept
      cases, e.g. the module name may be missing.  */
 
 # if PY_VERSION_HEX >= 0x030b0000
-  /* Note: PyType_GetQualName() was added in version 3.11.  */
-  PyObject *qualname = PyType_GetQualName (py_type);
+  /* Notes:
+     1. PyType_GetQualName() was added in version 3.11.
+     2. On one hand, PyType_GetQualName() relies internally on ht_qualname
+	which is supposed to never be NULL, therefore, does not set any Python
+	error.  On the other hand, PyType_GetQualName() calls internally
+	PyUnicode_AsUTF8AndSize(), which when erroring, sets a Python error
+	and returns NULL.  */
+  gdbpy_ref<> qualname (PyType_GetQualName (py_type));
   if (qualname == nullptr)
-    return nullptr;
-
-  return PyUnicode_AsUTF8AndSize (qualname, nullptr);
+    return handle_err ();
+  return pyobj_to_str (qualname.get ());
 
 # else
   /* In the absence of PyType_GetQualName(), fallback on using PyHeapTypeObject
@@ -58,15 +87,14 @@ gdb_py_tp_name (PyTypeObject *py_type) noexcept
      when the minimum supported Python version is increased above 3.10.  */
   PyHeapTypeObject *ht = (PyHeapTypeObject *) py_type;
   if (ht->ht_qualname == nullptr)
-    return nullptr;
-
-  return PyUnicode_AsUTF8AndSize (ht->ht_qualname, nullptr);
+    return NO_TYPE_NAME;
+  return pyobj_to_str (ht->ht_qualname);
 # endif
 #endif
 }
 
 /* Return the type's fully qualified name from a PyObject.  */
-const char *
+std::string
 gdbpy_py_obj_tp_name (PyObject *self) noexcept
 {
   /* Note: Py_TYPE () is part of the stable ABI since version 3.14.  */

gdb/python/py-obj-type.h

@@ -21,9 +21,9 @@
 #define GDB_PYTHON_PY_OBJ_TYPE_H
 
 /* Return the type's fully qualified name from a PyTypeObject.  */
-extern const char *gdb_py_tp_name (PyTypeObject *py_type) noexcept;
+extern std::string gdb_py_tp_name (PyTypeObject *py_type) noexcept;
 
 /* Return the type's fully qualified name from a PyObject.  */
-extern const char *gdbpy_py_obj_tp_name (PyObject *self) noexcept;
+extern std::string gdbpy_py_obj_tp_name (PyObject *self) noexcept;
 
 #endif /* GDB_PYTHON_PY_OBJ_TYPE_H */

gdb/python/py-style.c

@@ -269,7 +269,7 @@ stylepy_init_from_parts (PyObject *self, PyObject *fg, PyObject *bg,
       PyErr_Format
 	(PyExc_TypeError,
 	 _("'foreground' argument must be gdb.Color or None, not %s."),
-	 gdbpy_py_obj_tp_name (fg));
+	 gdbpy_py_obj_tp_name (fg).c_str ());
       return -1;
     }
 
@@ -278,7 +278,7 @@ stylepy_init_from_parts (PyObject *self, PyObject *fg, PyObject *bg,
       PyErr_Format
 	(PyExc_TypeError,
 	 _("'background' argument must be gdb.Color or None, not %s."),
-	 gdbpy_py_obj_tp_name (bg));
+	 gdbpy_py_obj_tp_name (bg).c_str ());
       return -1;
     }
 
@@ -485,7 +485,7 @@ stylepy_set_foreground (PyObject *self, PyObject *newvalue, void *closure)
   if (!gdbpy_is_color (newvalue))
     {
       PyErr_Format (PyExc_TypeError, _("value must be gdb.Color, not %s"),
-		    gdbpy_py_obj_tp_name (newvalue));
+		    gdbpy_py_obj_tp_name (newvalue).c_str ());
       return -1;
     }
 
@@ -543,7 +543,7 @@ stylepy_set_background (PyObject *self, PyObject *newvalue, void *closure)
   if (!gdbpy_is_color (newvalue))
     {
       PyErr_Format (PyExc_TypeError, _("value must be gdb.Color, not %s"),
-		    gdbpy_py_obj_tp_name (newvalue));
+		    gdbpy_py_obj_tp_name (newvalue).c_str ());
       return -1;
     }
 
@@ -625,7 +625,7 @@ stylepy_set_intensity (PyObject *self, PyObject *newvalue, void *closure)
       PyErr_Format
 	(PyExc_TypeError,
 	 _("value must be a Long (a gdb.INTENSITY constant), not %s"),
-	 gdbpy_py_obj_tp_name (newvalue));
+	 gdbpy_py_obj_tp_name (newvalue).c_str ());
       return -1;
     }
 
@@ -735,12 +735,12 @@ stylepy_repr (PyObject *self)
 
   if (style_obj->style_name == nullptr)
     return PyUnicode_FromFormat ("<%s fg=%s, bg=%s, intensity=%s>",
-				 gdbpy_py_obj_tp_name (self),
+				 gdbpy_py_obj_tp_name (self).c_str (),
 				 fg_str.get (), bg_str.get (),
 				 intensity_str);
   else
     return PyUnicode_FromFormat ("<%s name='%s', fg=%s, bg=%s, intensity=%s>",
-				 gdbpy_py_obj_tp_name (self),
+				 gdbpy_py_obj_tp_name (self).c_str (),
 				 style_obj->style_name, fg_str.get (),
 				 bg_str.get (), intensity_str);
 }

gdb/python/py-symbol.c

@@ -384,7 +384,7 @@ sympy_repr (PyObject *self)
     return gdb_py_invalid_object_repr (self);
 
   return PyUnicode_FromFormat ("<%s print_name=%s>",
-			       gdbpy_py_obj_tp_name (self),
+			       gdbpy_py_obj_tp_name (self).c_str (),
 			       symbol->print_name ());
 }
 

gdb/python/py-type.c

@@ -1086,7 +1086,7 @@ typy_repr (PyObject *self)
 				       host_charset (), NULL);
 
   return PyUnicode_FromFormat ("<%s code=%s name=%U>",
-			       gdbpy_py_obj_tp_name (self),
+			       gdbpy_py_obj_tp_name (self).c_str (),
 			       code, py_typename);
 }
 

gdb/python/py-unwind.c

@@ -252,7 +252,7 @@ unwind_infopy_repr (PyObject *self)
 
   if (pending_frame->frame_info == nullptr)
     return PyUnicode_FromFormat ("<%s for an invalid frame>",
-				 gdbpy_py_obj_tp_name (self));
+				 gdbpy_py_obj_tp_name (self).c_str ());
 
   std::string saved_reg_names;
   struct gdbarch *gdbarch = pending_frame->gdbarch;
@@ -268,7 +268,7 @@ unwind_infopy_repr (PyObject *self)
 
   const frame_info_ptr &frame (*pending_frame->frame_info);
   return PyUnicode_FromFormat ("<%s frame #%d, saved_regs=(%s)>",
-			       gdbpy_py_obj_tp_name (self),
+			       gdbpy_py_obj_tp_name (self).c_str (),
 			       frame_relative_level (frame),
 			       saved_reg_names.c_str ());
 }
@@ -464,7 +464,7 @@ pending_framepy_repr (PyObject *self)
     }
 
   return PyUnicode_FromFormat ("<%s level=%d, sp=%s, pc=%s>",
-			       gdbpy_py_obj_tp_name (self),
+			       gdbpy_py_obj_tp_name (self).c_str (),
 			       frame_relative_level (frame),
 			       sp_str,
 			       pc_str);
@@ -939,7 +939,7 @@ frame_unwind_python::sniff (const frame_info_ptr &this_frame,
   gdb_assert (pyo_unwind_info != nullptr);
   if (!PyObject_TypeCheck (pyo_unwind_info, &unwind_info_object_type))
     error (_("an Unwinder should return gdb.UnwindInfo, not %s."),
-	   gdbpy_py_obj_tp_name (pyo_unwind_info));
+	   gdbpy_py_obj_tp_name (pyo_unwind_info).c_str ());
 
   {
     unwind_info_object *unwind_info =

gdb/python/py-utils.c

@@ -362,7 +362,7 @@ gdb_py_generic_getattro (PyObject *self, PyObject *attr)
      Therefore, we must explicitly raise an AttributeError in this case.  */
   PyErr_Format (PyExc_AttributeError,
 		"'%s' object has no attribute '%s'",
-		gdbpy_py_obj_tp_name (self),
+		gdbpy_py_obj_tp_name (self).c_str (),
 		PyUnicode_AsUTF8AndSize (attr, nullptr));
   return nullptr;
 }
@@ -700,5 +700,6 @@ gdbpy_fix_doc_string_indentation (gdb::unique_xmalloc_ptr<char> doc)
 PyObject *
 gdb_py_invalid_object_repr (PyObject *self)
 {
-  return PyUnicode_FromFormat ("<%s (invalid)>", gdbpy_py_obj_tp_name (self));
+  return PyUnicode_FromFormat ("<%s (invalid)>",
+			       gdbpy_py_obj_tp_name (self).c_str ());
 }

gdb/python/python-internal.h

@@ -1132,15 +1132,18 @@ gdbpy_type_ready (PyTypeObject *type, PyObject *mod = nullptr)
 {
   if (PyType_Ready (type) < 0)
     return -1;
-  const char *tp_name = gdb_py_tp_name (type);
+  const auto &tp_name = gdb_py_tp_name (type);
+  std::string_view tp_name_s = tp_name;
   if (mod == nullptr)
     {
-      gdb_assert (startswith (tp_name, "gdb."));
+      gdb_assert (startswith (tp_name_s, "gdb."));
       mod = gdb_module;
     }
-  const char *dot = strrchr (tp_name, '.');
-  gdb_assert (dot != nullptr);
-  return gdb_pymodule_addobject (mod, dot + 1, (PyObject *) type);
+  const auto pos_dot = tp_name_s.find_last_of ('.');
+  gdb_assert (pos_dot != tp_name_s.npos);
+  return gdb_pymodule_addobject (mod,
+				 tp_name_s.substr (pos_dot + 1).data (),
+				 (PyObject *) type);
 }
 
 /* Poison PyType_Ready.  Only gdbpy_type_ready should be used, to

gdb/python/python.c

@@ -1581,7 +1581,7 @@ gdbpy_write (PyObject *self, PyObject *args, PyObject *kw)
       PyErr_Format
 	(PyExc_TypeError,
 	 _("'style' argument must be gdb.Style or None, not %s."),
-	 gdbpy_py_obj_tp_name (style_obj));
+	 gdbpy_py_obj_tp_name (style_obj).c_str ());
       return nullptr;
     }