diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index c12d9527..de7dd0b0 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -64,7 +64,7 @@ jobs:
             castxml-epic: 1
             cppstd: "-std=c++11"
 
-          - os: macos-latest
+          - os: macos-12
             compiler: xcode
             version: "default"
             python-version: "3.8"
@@ -90,7 +90,7 @@ jobs:
         run: |
           wget -q -O - https://data.kitware.com/api/v1/file/hashsum/sha512/bdbb67a10c5f8d1b738cd19cb074f409d4803e8077cb8c1072ef4eaf738fa871a73643f9c8282d58cae28d188df842c82ad6620b6d590b0396a0172a27438dce/download | tar zxf - -C ~/
       - name: Setup castxml for Mac
-        if: matrix.os == 'macos-latest'
+        if: matrix.os == 'macos-12'
         run: |
           wget -q -O - https://data.kitware.com/api/v1/file/hashsum/sha512/5d937e938f7b882a3a3e7941e68f8312d0898aaf2082e00003dd362b1ba70b98b0a08706a1be28e71652a6a0f1e66f89768b5eaa20e5a100592d5b3deefec3f0/download | tar zxf - -C ~/
       - name: Setup castxml config
@@ -102,12 +102,3 @@ jobs:
           coverage run -m unittests.test_all
           coverage combine
           coverage xml
-      - name: Upload coverage to Codecov
-        uses: codecov/codecov-action@v3
-        with:
-          token: ${{ secrets.CODECOV_TOKEN }}
-          file: coverage.xml
-          flags: unittests
-          env_vars: OS,PYTHON
-          name: codecov-umbrella
-          fail_ci_if_error: true
diff --git a/CHANGELOG.md b/CHANGELOG.md
index db53506c..a27edbe0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,16 @@
 Changes
 =======
 
+Version 2.5.0
+-------------
+
+1. Add support for new cxx versions in cxx_standard class
+
+2. Deprecate utils.is_str
+
+3. pyproject.toml improvements
+
+
 Version 2.4.0
 -------------
 
diff --git a/pyproject.toml b/pyproject.toml
index 7d4bce6e..de3e3f10 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,5 +1,6 @@
 [build-system]
-requires = ["setuptools", "wheel"]
+requires = ["setuptools"]
+build-backend = "setuptools.build_meta"
 
 [project]
 name = "pygccxml"
@@ -17,7 +18,7 @@ keywords = [
   "CastXML",
   "gccxml",
 ]
-version = "2.4.0"
+version = "2.5.0"
 
 classifiers = [
   "Development Status :: 5 - Production/Stable",
diff --git a/src/pygccxml/declarations/container_traits.py b/src/pygccxml/declarations/container_traits.py
index 92ad175b..d4f6658e 100644
--- a/src/pygccxml/declarations/container_traits.py
+++ b/src/pygccxml/declarations/container_traits.py
@@ -522,7 +522,7 @@ def remove_defaults(self, type_or_string):
         """
 
         name = type_or_string
-        if not utils.is_str(type_or_string):
+        if not isinstance(type_or_string, str):
             name = self.class_declaration(type_or_string).name
         if not self.remove_defaults_impl:
             return name
@@ -705,7 +705,7 @@ def find_container_traits(cls_or_string):
         declarations.container_traits: a container traits
     """
 
-    if utils.is_str(cls_or_string):
+    if isinstance(cls_or_string, str):
         if not templates.is_instantiation(cls_or_string):
             return None
         name = templates.name(cls_or_string)
diff --git a/src/pygccxml/declarations/type_traits.py b/src/pygccxml/declarations/type_traits.py
index eef8fe7a..bc9be8de 100644
--- a/src/pygccxml/declarations/type_traits.py
+++ b/src/pygccxml/declarations/type_traits.py
@@ -507,7 +507,7 @@ def is_std_string(type_):
 
     """
 
-    if utils.is_str(type_):
+    if isinstance(type_, str):
         return type_ in string_equivalences
 
     type_ = remove_alias(type_)
@@ -522,7 +522,7 @@ def is_std_wstring(type_):
 
     """
 
-    if utils.is_str(type_):
+    if isinstance(type_, str):
         return type_ in wstring_equivalences
 
     type_ = remove_alias(type_)
@@ -537,7 +537,7 @@ def is_std_ostream(type_):
 
     """
 
-    if utils.is_str(type_):
+    if isinstance(type_, str):
         return type_ in ostream_equivalences
 
     type_ = remove_alias(type_)
@@ -552,7 +552,7 @@ def is_std_wostream(type_):
 
     """
 
-    if utils.is_str(type_):
+    if isinstance(type_, str):
         return type_ in wostream_equivalences
 
     type_ = remove_alias(type_)
diff --git a/src/pygccxml/parser/config.py b/src/pygccxml/parser/config.py
index e2b9eea4..e2db56d8 100644
--- a/src/pygccxml/parser/config.py
+++ b/src/pygccxml/parser/config.py
@@ -22,7 +22,6 @@
     from ConfigParser import SafeConfigParser as ConfigParser
 except ImportError:
     from configparser import ConfigParser
-from .. import utils
 
 
 class parser_configuration_t(object):
@@ -383,7 +382,7 @@ def load_xml_generator_configuration(configuration, **defaults):
 
     """
     parser = configuration
-    if utils.is_str(configuration):
+    if isinstance(configuration, str):
         parser = ConfigParser()
         parser.read(configuration)
 
diff --git a/src/pygccxml/parser/linker.py b/src/pygccxml/parser/linker.py
index b7aeda3b..1677e27f 100644
--- a/src/pygccxml/parser/linker.py
+++ b/src/pygccxml/parser/linker.py
@@ -4,7 +4,6 @@
 # See http://www.boost.org/LICENSE_1_0.txt
 
 from pygccxml import declarations
-from .. import utils
 
 
 class linker_t(
@@ -304,7 +303,7 @@ def visit_member_variable_type(self):
         self.__link_compound_type()
 
     def visit_declarated(self):
-        if utils.is_str(self.__inst.declaration):
+        if isinstance(self.__inst.declaration, str):
             self.__inst.declaration = self.__decls[self.__inst.declaration]
 
     def visit_restrict(self):
diff --git a/src/pygccxml/parser/project_reader.py b/src/pygccxml/parser/project_reader.py
index a6287907..d7bf7c99 100644
--- a/src/pygccxml/parser/project_reader.py
+++ b/src/pygccxml/parser/project_reader.py
@@ -187,7 +187,7 @@ def __init__(self, config, cache=None, decl_factory=None):
         self.__dcache = None
         if isinstance(cache, declarations_cache.cache_base_t):
             self.__dcache = cache
-        elif utils.is_str(cache):
+        elif isinstance(cache, str):
             self.__dcache = declarations_cache.file_cache_t(cache)
         else:
             self.__dcache = declarations_cache.dummy_cache_t()
@@ -221,7 +221,7 @@ def get_os_file_names(files):
 
         fnames = []
         for f in files:
-            if utils.is_str(f):
+            if isinstance(f, str):
                 fnames.append(f)
             elif isinstance(f, file_configuration_t):
                 if f.content_type in (
diff --git a/src/pygccxml/parser/scanner.py b/src/pygccxml/parser/scanner.py
index 4368a84a..63f9cbd7 100644
--- a/src/pygccxml/parser/scanner.py
+++ b/src/pygccxml/parser/scanner.py
@@ -334,7 +334,7 @@ def startElement(self, name, attrs):
                 self.__update_membership(attrs)
                 self.__read_attributes(obj, attrs)
 
-            elif utils.is_str(obj):
+            elif isinstance(obj, str):
 
                 self.__files[element_id] = os.path.normpath(obj)
 
diff --git a/src/pygccxml/utils/utils.py b/src/pygccxml/utils/utils.py
index 21bb5d3c..7a9deb5a 100644
--- a/src/pygccxml/utils/utils.py
+++ b/src/pygccxml/utils/utils.py
@@ -26,6 +26,11 @@ def is_str(string):
         bool: True or False
 
     """
+    warnings.warn(
+        "The is_str function is deprecated. \
+        Use isinstance(string, str) instead.",
+        DeprecationWarning)
+
     if sys.version_info[:2] >= (3, 0):
         return isinstance(string, str)
 
@@ -50,35 +55,12 @@ def find_xml_generator(name="castxml", search_path=None):
 
     """
 
-    if sys.version_info[:2] >= (3, 3):
-        path = _find_xml_generator_for_python_greater_equals_33(
-            name, search_path=search_path)
-    else:
-        path = _find_xml_generator_for_legacy_python(name)
-
+    path = shutil.which(name, path=search_path)
     if path == "" or path is None:
         raise Exception("No c++ parser found. Please install castxml.")
     return path.rstrip(), name
 
 
-def _find_xml_generator_for_python_greater_equals_33(name, search_path=None):
-    return shutil.which(name, path=search_path)
-
-
-def _find_xml_generator_for_legacy_python(name):
-    if platform.system() == "Windows":
-        command = "where"
-    else:
-        command = "which"
-    p = subprocess.Popen([command, name], stdout=subprocess.PIPE,
-                         stderr=subprocess.PIPE)
-    path = p.stdout.read().decode("utf-8")
-    p.wait()
-    p.stdout.close()
-    p.stderr.close()
-    return path.rstrip()
-
-
 def _create_logger_(name):
     """Implementation detail, creates a logger."""
     logger = logging.getLogger(name)
@@ -295,8 +277,12 @@ class cxx_standard(object):
         '-std=c++17': 201703,
         '-std=gnu++1z': 201703,
         '-std=gnu++17': 201703,
-        '-std=c++2a': float('inf'),
-        '-std=gnu++2a': float('inf'),
+        '-std=c++2a': 202002,
+        '-std=gnu++2a': 202002,
+        '-std=c++20': 202002,
+        '-std=gnu++20': 202002,
+        '-std=c++23': float('inf'),
+        '-std=gnu++23': float('inf'),
     }
 
     def __init__(self, cflags):
diff --git a/unittests/find_container_traits_tester.py b/unittests/find_container_traits_tester.py
index c6eebce5..1571c373 100644
--- a/unittests/find_container_traits_tester.py
+++ b/unittests/find_container_traits_tester.py
@@ -9,7 +9,6 @@
 
 from pygccxml import parser
 from pygccxml import declarations
-from pygccxml import utils
 
 
 class Test(parser_test_case.parser_test_case_t):
@@ -30,7 +29,7 @@ def setUp(self):
         self.global_ns = Test.global_ns
 
     def __cmp_traits(self, typedef, expected, partial_name, key_type=None):
-        if utils.is_str(typedef):
+        if isinstance(typedef, str):
             typedef = self.global_ns.typedef(typedef)
         traits = declarations.find_container_traits(typedef)
         self.assertTrue(
diff --git a/unittests/misc/profile_parser.py b/unittests/misc/profile_parser.py
deleted file mode 100644
index 47ab3eb3..00000000
--- a/unittests/misc/profile_parser.py
+++ /dev/null
@@ -1,21 +0,0 @@
-# Copyright 2014-2017 Insight Software Consortium.
-# Copyright 2004-2009 Roman Yakovenko.
-# Distributed under the Boost Software License, Version 1.0.
-# See http://www.boost.org/LICENSE_1_0.txt
-
-import os
-import hotshot
-import hotshot.stats
-
-import autoconfig
-import test_parser
-
-if __name__ == "__main__":
-    statistics_file = os.path.join(autoconfig.data_directory, 'profile.stat')
-    profile = hotshot.Profile(statistics_file)
-    profile.runcall(test_parser.run_suite)
-    profile.close()
-    statistics = hotshot.stats.load(statistics_file)
-    statistics.strip_dirs()
-    statistics.sort_stats('time', 'calls')
-    statistics.print_stats(20)
diff --git a/unittests/misc/test_performance.py b/unittests/misc/test_performance.py
deleted file mode 100644
index d5a135ce..00000000
--- a/unittests/misc/test_performance.py
+++ /dev/null
@@ -1,160 +0,0 @@
-# Copyright 2014-2017 Insight Software Consortium.
-# Copyright 2004-2009 Roman Yakovenko.
-# Distributed under the Boost Software License, Version 1.0.
-# See http://www.boost.org/LICENSE_1_0.txt
-
-import os
-import sys
-import timeit
-import hotshot
-import hotshot.stats
-
-this_module_dir_path = os.path.abspath(
-    os.path.dirname(sys.modules[__name__].__file__))
-
-sys.path.insert(1, os.path.join(this_module_dir_path, '../../'))
-sys.path.insert(2, os.path.join(this_module_dir_path, '../'))
-
-import autoconfig  # nopep8
-from pygccxml import parser  # nopep8
-from pygccxml import declarations  # nopep8
-
-dcache_file_name = os.path.join(autoconfig.data_directory, 'pygccxml.cache')
-if os.path.exists(dcache_file_name):
-    os.remove(dcache_file_name)
-
-
-def test_on_windows_dot_h():
-    he = r"2003\Vc7\PlatformSDK\Include\windows.h"
-    windows_header = r"D:\Program Files\Microsoft Visual Studio .NET " + he
-    clock_prev = timeit.default_timer()
-    dcache = parser.file_cache_t(dcache_file_name)
-    reader = parser.source_reader_t(
-        parser.xml_generator_configuration_t(
-            xml_generator_path=autoconfig.generator_path),
-        dcache)
-    reader.read_file(windows_header)
-    dcache.flush()
-    clock_now = timeit.default_timer()
-    print('without cache: %f seconds' % (clock_now - clock_prev))
-
-    clock_prev = timeit.default_timer()
-    dcache = parser.file_cache_t(dcache_file_name)
-    reader = parser.source_reader_t(
-        parser.xml_generator_configuration_t(
-            xml_generator_path=autoconfig.generator_path),
-        dcache)
-    reader.read_file(windows_header)
-    clock_now = timeit.default_timer()
-    print('with cache   : %f seconds' % (clock_now - clock_prev))
-
-#########################################################################
-# testing include_std.hpp
-
-
-def test_source_on_include_std_dot_hpp():
-    include_std_header = os.path.join(
-        autoconfig.data_directory,
-        'include_std.hpp')
-    clock_prev = timeit.default_timer()
-    dcache = parser.file_cache_t(dcache_file_name)
-    reader = parser.source_reader_t(
-        parser.xml_generator_configuration_t(
-            xml_generator_path=autoconfig.generator_path),
-        dcache)
-    reader.read_file(include_std_header)
-    dcache.flush()
-    clock_now = timeit.default_timer()
-    print('without cache: %f seconds' % (clock_now - clock_prev))
-
-    clock_prev = timeit.default_timer()
-    dcache = parser.file_cache_t(dcache_file_name)
-    reader = parser.source_reader_t(
-        parser.xml_generator_configuration_t(
-            xml_generator_path=autoconfig.generator_path),
-        dcache)
-    reader.read_file(include_std_header)
-    clock_now = timeit.default_timer()
-    print('with cache   : %f seconds' % (clock_now - clock_prev))
-
-
-#########################################################################
-# testing include_std.hpp
-def test_project_on_include_std_dot_hpp():
-    include_std_header = os.path.join(
-        autoconfig.data_directory,
-        'include_std.hpp')
-    clock_prev = timeit.default_timer()
-    dcache = parser.file_cache_t(dcache_file_name)
-    reader = parser.project_reader_t(
-        parser.xml_generator_configuration_t(
-            xml_generator_path=autoconfig.generator_path),
-        dcache)
-    reader.read_files([include_std_header])
-    dcache.flush()
-    clock_now = timeit.default_timer()
-    print('without cache: %f seconds' % (clock_now - clock_prev))
-
-    clock_prev = timeit.default_timer()
-    dcache = parser.file_cache_t(dcache_file_name)
-    reader = parser.project_reader_t(
-        parser.xml_generator_configuration_t(
-            xml_generator_path=autoconfig.generator_path),
-        dcache)
-    reader.read_files([include_std_header])
-    clock_now = timeit.default_timer()
-    print('with cache   : %f seconds' % (clock_now - clock_prev))
-
-
-def profile_project():
-    include_std_header = os.path.join(
-        autoconfig.data_directory,
-        'include_std.hpp')
-    reader = parser.project_reader_t(
-        parser.xml_generator_configuration_t(
-            xml_generator_path=autoconfig.generator_path))
-    reader.read_files([include_std_header])
-
-
-def profile_project2():
-    he = r"2003\Vc7\PlatformSDK\Include\windows.h"
-    include_std_header = r"D:\Program Files\Microsoft Visual Studio .NET " + he
-    reader = parser.project_reader_t(
-        parser.xml_generator_configuration_t(
-            xml_generator_path=autoconfig.generator_path))
-    reader.read_files([include_std_header])
-
-
-def test_on_big_file(file_name, count):
-    file_name = os.path.join(autoconfig.data_directory, file_name)
-    for i in range(count):
-        reader = parser.project_reader_t(
-            parser.xml_generator_configuration_t(
-                xml_generator_path=autoconfig.generator_path))
-        decls = reader.read_files([parser.create_gccxml_fc(file_name)])
-        global_ns = declarations.get_global_namespace(decls)
-        global_ns.init_optimizer()
-
-
-if __name__ == "__main__":
-
-    # test_on_windows_dot_h()
-    # test_source_on_include_std_dot_hpp()
-    # test_project_on_include_std_dot_hpp()
-    print('running')
-    prof = hotshot.Profile('parser.prof')
-    prof.runcall(lambda: test_on_big_file('itkImage.xml', 1))
-    stats = hotshot.stats.load("parser.prof")
-    stats.sort_stats('time', 'calls')
-    stats.print_stats(30)
-    print('running - done')
-    # print 'loading file'
-    # pdata = pstats.Stats('pygccxml.profile')
-    # print 'loading file - done'
-    # print 'striping dirs'
-    # pdata.strip_dirs()
-    # print 'striping dirs - done'
-    # print 'sorting stats'
-    # pdata.sort_stats('time').print_stats(476)
-    # print 'sorting stats - done'
-    # pdata.print_callers('find_all_declarations')
diff --git a/unittests/misc/timeit_test_parser.py b/unittests/misc/timeit_test_parser.py
deleted file mode 100644
index 148c261a..00000000
--- a/unittests/misc/timeit_test_parser.py
+++ /dev/null
@@ -1,15 +0,0 @@
-# Copyright 2014-2017 Insight Software Consortium.
-# Copyright 2004-2009 Roman Yakovenko.
-# Distributed under the Boost Software License, Version 1.0.
-# See http://www.boost.org/LICENSE_1_0.txt
-
-from timeit import Timer
-
-stmt = """
-import unittest
-from test_parser import create_suite
-unittest.TextTestRunner(verbosity=2).run( create_suite() )
-"""
-
-timer = Timer(stmt)
-print(timer.timeit(3))