diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst
index bd90e37ea27cf6..232a2e98789d2b 100644
--- a/Doc/reference/datamodel.rst
+++ b/Doc/reference/datamodel.rst
@@ -1032,7 +1032,10 @@ Special attributes
        .. versionadded:: 3.13
 
    * - .. attribute:: type.__firstlineno__
-     - The line number of the first line of the class definition, including decorators.
+     - The line number of the first line of the class definition,
+       including decorators.
+       Setting the :attr:`__module__` attribute removes the
+       :attr:`!__firstlineno__` item from the type's dictionary.
 
        .. versionadded:: 3.13
 
diff --git a/Lib/collections/abc.py b/Lib/collections/abc.py
index 86ca8b8a8414b3..034ba377a0dbec 100644
--- a/Lib/collections/abc.py
+++ b/Lib/collections/abc.py
@@ -1,3 +1,3 @@
-from _collections_abc import *
-from _collections_abc import __all__
-from _collections_abc import _CallableGenericAlias
+import _collections_abc
+import sys
+sys.modules[__name__] = _collections_abc
diff --git a/Lib/decimal.py b/Lib/decimal.py
index 4d8e15cb68ff0c..ee3147f5dde270 100644
--- a/Lib/decimal.py
+++ b/Lib/decimal.py
@@ -103,6 +103,7 @@
     from _decimal import __version__
     from _decimal import __libmpdec_version__
 except ImportError:
-    from _pydecimal import *
-    from _pydecimal import __version__
-    from _pydecimal import __libmpdec_version__
+    import _pydecimal
+    import sys
+    _pydecimal.__doc__ = __doc__
+    sys.modules[__name__] = _pydecimal
diff --git a/Lib/inspect.py b/Lib/inspect.py
index 9499dc5c6dc81c..8df2383f60b011 100644
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -1082,10 +1082,12 @@ def findsource(object):
 
     if isclass(object):
         try:
-            firstlineno = vars(object)['__firstlineno__']
+            lnum = vars(object)['__firstlineno__'] - 1
         except (TypeError, KeyError):
             raise OSError('source code not available')
-        return lines, firstlineno - 1
+        if lnum >= len(lines):
+            raise OSError('lineno is out of bounds')
+        return lines, lnum
 
     if ismethod(object):
         object = object.__func__
diff --git a/Lib/test/test_builtin.py b/Lib/test/test_builtin.py
index c5394def80e9a9..3a5531924976f7 100644
--- a/Lib/test/test_builtin.py
+++ b/Lib/test/test_builtin.py
@@ -2564,6 +2564,7 @@ def test_new_type(self):
         self.assertEqual(A.__module__, __name__)
         self.assertEqual(A.__bases__, (object,))
         self.assertIs(A.__base__, object)
+        self.assertNotIn('__firstlineno__', A.__dict__)
         x = A()
         self.assertIs(type(x), A)
         self.assertIs(x.__class__, A)
@@ -2642,6 +2643,17 @@ def test_type_qualname(self):
             A.__qualname__ = b'B'
         self.assertEqual(A.__qualname__, 'D.E')
 
+    def test_type_firstlineno(self):
+        A = type('A', (), {'__firstlineno__': 42})
+        self.assertEqual(A.__name__, 'A')
+        self.assertEqual(A.__module__, __name__)
+        self.assertEqual(A.__dict__['__firstlineno__'], 42)
+        A.__module__ = 'testmodule'
+        self.assertEqual(A.__module__, 'testmodule')
+        self.assertNotIn('__firstlineno__', A.__dict__)
+        A.__firstlineno__ = 43
+        self.assertEqual(A.__dict__['__firstlineno__'], 43)
+
     def test_type_typeparams(self):
         class A[T]:
             pass
diff --git a/Lib/test/test_decimal.py b/Lib/test/test_decimal.py
index 12479e32d0f5db..c591fd54430b18 100644
--- a/Lib/test/test_decimal.py
+++ b/Lib/test/test_decimal.py
@@ -4381,7 +4381,8 @@ def test_module_attributes(self):
 
         self.assertEqual(C.__version__, P.__version__)
 
-        self.assertEqual(dir(C), dir(P))
+        self.assertLessEqual(set(dir(C)), set(dir(P)))
+        self.assertEqual([n for n in dir(C) if n[:2] != '__'], sorted(P.__all__))
 
     def test_context_attributes(self):
 
diff --git a/Lib/test/test_inspect/inspect_fodder2.py b/Lib/test/test_inspect/inspect_fodder2.py
index 43e9f852022934..43fda6622537fc 100644
--- a/Lib/test/test_inspect/inspect_fodder2.py
+++ b/Lib/test/test_inspect/inspect_fodder2.py
@@ -357,3 +357,15 @@ class td354(typing.TypedDict):
 
 # line 358
 td359 = typing.TypedDict('td359', (('x', int), ('y', int)))
+
+import dataclasses
+
+# line 363
+@dataclasses.dataclass
+class dc364:
+    x: int
+    y: int
+
+# line 369
+dc370 = dataclasses.make_dataclass('dc370', (('x', int), ('y', int)))
+dc371 = dataclasses.make_dataclass('dc370', (('x', int), ('y', int)), module=__name__)
diff --git a/Lib/test/test_inspect/test_inspect.py b/Lib/test/test_inspect/test_inspect.py
index 766b3fe571b5f9..e2e4f1230abd50 100644
--- a/Lib/test/test_inspect/test_inspect.py
+++ b/Lib/test/test_inspect/test_inspect.py
@@ -838,6 +838,47 @@ class C:
             nonlocal __firstlineno__
         self.assertRaises(OSError, inspect.getsource, C)
 
+class TestGetsourceStdlib(unittest.TestCase):
+    # Test Python implementations of the stdlib modules
+
+    def test_getsource_stdlib_collections_abc(self):
+        import collections.abc
+        lines, lineno = inspect.getsourcelines(collections.abc.Sequence)
+        self.assertEqual(lines[0], 'class Sequence(Reversible, Collection):\n')
+        src = inspect.getsource(collections.abc.Sequence)
+        self.assertEqual(src.splitlines(True), lines)
+
+    def test_getsource_stdlib_tomllib(self):
+        import tomllib
+        self.assertRaises(OSError, inspect.getsource, tomllib.TOMLDecodeError)
+        self.assertRaises(OSError, inspect.getsourcelines, tomllib.TOMLDecodeError)
+
+    def test_getsource_stdlib_abc(self):
+        # Pure Python implementation
+        abc = import_helper.import_fresh_module('abc', blocked=['_abc'])
+        with support.swap_item(sys.modules, 'abc', abc):
+            self.assertRaises(OSError, inspect.getsource, abc.ABCMeta)
+            self.assertRaises(OSError, inspect.getsourcelines, abc.ABCMeta)
+        # With C acceleration
+        import abc
+        try:
+            src = inspect.getsource(abc.ABCMeta)
+            lines, lineno = inspect.getsourcelines(abc.ABCMeta)
+        except OSError:
+            pass
+        else:
+            self.assertEqual(lines[0], '    class ABCMeta(type):\n')
+            self.assertEqual(src.splitlines(True), lines)
+
+    def test_getsource_stdlib_decimal(self):
+        # Pure Python implementation
+        decimal = import_helper.import_fresh_module('decimal', blocked=['_decimal'])
+        with support.swap_item(sys.modules, 'decimal', decimal):
+            src = inspect.getsource(decimal.Decimal)
+            lines, lineno = inspect.getsourcelines(decimal.Decimal)
+        self.assertEqual(lines[0], 'class Decimal(object):\n')
+        self.assertEqual(src.splitlines(True), lines)
+
 class TestGetsourceInteractive(unittest.TestCase):
     def test_getclasses_interactive(self):
         # bpo-44648: simulate a REPL session;
@@ -950,6 +991,11 @@ def test_typeddict(self):
         self.assertSourceEqual(mod2.td354, 354, 356)
         self.assertRaises(OSError, inspect.getsource, mod2.td359)
 
+    def test_dataclass(self):
+        self.assertSourceEqual(mod2.dc364, 364, 367)
+        self.assertRaises(OSError, inspect.getsource, mod2.dc370)
+        self.assertRaises(OSError, inspect.getsource, mod2.dc371)
+
 class TestBlockComments(GetSourceBase):
     fodderModule = mod
 
@@ -1013,7 +1059,7 @@ def test_findsource_without_filename(self):
             self.assertRaises(IOError, inspect.findsource, co)
             self.assertRaises(IOError, inspect.getsource, co)
 
-    def test_findsource_with_out_of_bounds_lineno(self):
+    def test_findsource_on_func_with_out_of_bounds_lineno(self):
         mod_len = len(inspect.getsource(mod))
         src = '\n' * 2* mod_len + "def f(): pass"
         co = compile(src, mod.__file__, "exec")
@@ -1021,9 +1067,20 @@ def test_findsource_with_out_of_bounds_lineno(self):
         eval(co, g, l)
         func = l['f']
         self.assertEqual(func.__code__.co_firstlineno, 1+2*mod_len)
-        with self.assertRaisesRegex(IOError, "lineno is out of bounds"):
+        with self.assertRaisesRegex(OSError, "lineno is out of bounds"):
             inspect.findsource(func)
 
+    def test_findsource_on_class_with_out_of_bounds_lineno(self):
+        mod_len = len(inspect.getsource(mod))
+        src = '\n' * 2* mod_len + "class A: pass"
+        co = compile(src, mod.__file__, "exec")
+        g, l = {'__name__': mod.__name__}, {}
+        eval(co, g, l)
+        cls = l['A']
+        self.assertEqual(cls.__firstlineno__, 1+2*mod_len)
+        with self.assertRaisesRegex(OSError, "lineno is out of bounds"):
+            inspect.findsource(cls)
+
     def test_getsource_on_method(self):
         self.assertSourceEqual(mod2.ClassWithMethod.method, 118, 119)
 
diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2024-09-02-20-36-45.gh-issue-123339.QcmpSs.rst b/Misc/NEWS.d/next/Core_and_Builtins/2024-09-02-20-36-45.gh-issue-123339.QcmpSs.rst
new file mode 100644
index 00000000000000..25b47d5fbaefa5
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2024-09-02-20-36-45.gh-issue-123339.QcmpSs.rst
@@ -0,0 +1,3 @@
+Setting the :attr:`!__module__` attribute for a class now removes the
+``__firstlineno__`` item from the type's dict, so they will no longer be
+inconsistent.
diff --git a/Misc/NEWS.d/next/Library/2024-09-02-20-34-04.gh-issue-123339.czgcSu.rst b/Misc/NEWS.d/next/Library/2024-09-02-20-34-04.gh-issue-123339.czgcSu.rst
new file mode 100644
index 00000000000000..e388541f1c2c19
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2024-09-02-20-34-04.gh-issue-123339.czgcSu.rst
@@ -0,0 +1,4 @@
+Fix :func:`inspect.getsource` for classes in :mod:`collections.abc` and
+:mod:`decimal` (for pure Python implementation) modules.
+:func:`inspect.getcomments` now raises OSError instead of IndexError if the
+``__firstlineno__`` value for a class is out of bound.
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index 16acb8b682d796..c911c3020039ab 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -1351,6 +1351,9 @@ type_set_module(PyTypeObject *type, PyObject *value, void *context)
     PyType_Modified(type);
 
     PyObject *dict = lookup_tp_dict(type);
+    if (PyDict_Pop(dict, &_Py_ID(__firstlineno__), NULL) < 0) {
+        return -1;
+    }
     return PyDict_SetItem(dict, &_Py_ID(__module__), value);
 }