diff --git a/.waf-tools/default-compiler-flags.py b/.waf-tools/default-compiler-flags.py
index 681913f..c8ab164 100644
--- a/.waf-tools/default-compiler-flags.py
+++ b/.waf-tools/default-compiler-flags.py
@@ -11,29 +11,32 @@
     conf.start_msg('Checking C++ compiler version')
 
     cxx = conf.env.CXX_NAME # generic name of the compiler
-    ccver = tuple(int(i) for i in conf.env.CC_VERSION)
+    ccver = get_compiler_ver(conf)
     ccverstr = '.'.join(conf.env.CC_VERSION)
     errmsg = ''
     warnmsg = ''
     if cxx == 'gcc':
-        if ccver < (7, 4, 0):
+        if ccver < (9, 1, 0):
             errmsg = ('The version of gcc you are using is too old.\n'
-                      'The minimum supported gcc version is 9.3.')
-        elif ccver < (9, 3, 0):
-            warnmsg = ('Using a version of gcc older than 9.3 is not '
+                      'The minimum supported gcc version is 10.2.')
+        elif ccver < (10, 2, 0):
+            warnmsg = ('Using a version of gcc older than 10.2 is not '
                        'officially supported and may result in build failures.')
         conf.flags = GccFlags()
     elif cxx == 'clang':
         if Utils.unversioned_sys_platform() == 'darwin':
-            if ccver < (10, 0, 0):
+            if ccver < (11, 0, 0):
                 errmsg = ('The version of Xcode you are using is too old.\n'
-                          'The minimum supported Xcode version is 12.4.')
-            elif ccver < (12, 0, 0):
-                warnmsg = ('Using a version of Xcode older than 12.4 is not '
+                          'The minimum supported Xcode version is 13.0.')
+            elif ccver < (13, 0, 0):
+                warnmsg = ('Using a version of Xcode older than 13.0 is not '
                            'officially supported and may result in build failures.')
         elif ccver < (7, 0, 0):
             errmsg = ('The version of clang you are using is too old.\n'
-                      'The minimum supported clang version is 7.0.')
+                      'The minimum supported clang version is 10.0.')
+        elif ccver < (10, 0, 0):
+            warnmsg = ('Using a version of clang older than 10.0 is not '
+                       'officially supported and may result in build failures.')
         conf.flags = ClangFlags()
     else:
         warnmsg = f'{cxx} compiler is unsupported'
@@ -57,6 +60,10 @@
     conf.env.DEFINES += generalFlags['DEFINES']
 
 
+def get_compiler_ver(conf):
+    return tuple(int(i) for i in conf.env.CC_VERSION)
+
+
 @Configure.conf
 def check_compiler_flags(conf):
     # Debug or optimized CXXFLAGS and LINKFLAGS are applied only if the
@@ -121,9 +128,6 @@
 
 
 class CompilerFlags:
-    def getCompilerVersion(self, conf):
-        return tuple(int(i) for i in conf.env.CC_VERSION)
-
     def getGeneralFlags(self, conf):
         """Get dict of CXXFLAGS, LINKFLAGS, and DEFINES that are always needed"""
         return {'CXXFLAGS': [], 'LINKFLAGS': [], 'DEFINES': []}
@@ -223,7 +227,7 @@
         elif Utils.unversioned_sys_platform() == 'freebsd':
             # Bug #4790
             flags['CXXFLAGS'] += [['-isystem', '/usr/local/include']]
-        if self.getCompilerVersion(conf) >= (18, 0, 0):
+        if get_compiler_ver(conf) >= (18, 0, 0) and get_compiler_ver(conf) < (20, 1, 0):
             # Bug #5300
             flags['CXXFLAGS'] += ['-Wno-enum-constexpr-conversion']
         return flags
@@ -237,10 +241,10 @@
         flags = super().getDebugFlags(conf)
         flags['CXXFLAGS'] += self.__cxxFlags
         # Enable assertions in libc++
-        if self.getCompilerVersion(conf) >= (18, 0, 0):
+        if get_compiler_ver(conf) >= (18, 0, 0):
             # https://libcxx.llvm.org/Hardening.html
             flags['DEFINES'] += ['_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_EXTENSIVE']
-        elif self.getCompilerVersion(conf) >= (15, 0, 0):
+        elif get_compiler_ver(conf) >= (15, 0, 0):
             # https://releases.llvm.org/15.0.0/projects/libcxx/docs/UsingLibcxx.html#enabling-the-safe-libc-mode
             flags['DEFINES'] += ['_LIBCPP_ENABLE_ASSERTIONS=1']
         # Tell libc++ to avoid including transitive headers
diff --git a/.waf-tools/sphinx.py b/.waf-tools/sphinx.py
new file mode 100644
index 0000000..7fccd64
--- /dev/null
+++ b/.waf-tools/sphinx.py
@@ -0,0 +1,77 @@
+# inspired by code by Hans-Martin von Gaudecker, 2012
+
+"""Support for Sphinx documentation"""
+
+import os
+from waflib import Task, TaskGen
+
+
+class sphinx_build(Task.Task):
+    color = 'BLUE'
+    run_str = '${SPHINX_BUILD} -q -b ${BUILDERNAME} -D ${VERSION} -D ${RELEASE} -d ${DOCTREEDIR} ${SRCDIR} ${OUTDIR}'
+
+    def keyword(self):
+        return f'Processing ({self.env.BUILDERNAME})'
+
+
+# from https://docs.python.org/3.12/whatsnew/3.12.html#imp
+def load_source(modname, filename):
+    import importlib.util
+    from importlib.machinery import SourceFileLoader
+    loader = SourceFileLoader(modname, filename)
+    spec = importlib.util.spec_from_file_location(modname, filename, loader=loader)
+    module = importlib.util.module_from_spec(spec)
+    loader.exec_module(module)
+    return module
+
+
+@TaskGen.feature('sphinx')
+@TaskGen.before_method('process_source')
+def process_sphinx(self):
+    """Set up the task generator with a Sphinx instance and create a task."""
+
+    conf = self.path.find_node(self.config)
+    if not conf:
+        self.bld.fatal(f'Sphinx configuration file {repr(self.config)} not found')
+
+    inputs = [conf] + self.to_nodes(self.source)
+    task = self.create_task('sphinx_build', inputs, always_run=getattr(self, 'always', False))
+
+    confdir = conf.parent.abspath()
+    buildername = getattr(self, 'builder', 'html')
+    srcdir = getattr(self, 'srcdir', confdir)
+    outdir = self.path.find_or_declare(getattr(self, 'outdir', buildername)).get_bld()
+    doctreedir = getattr(self, 'doctreedir', os.path.join(outdir.abspath(), '.doctrees'))
+    release = getattr(self, 'release', self.version)
+
+    task.env['BUILDERNAME'] = buildername
+    task.env['SRCDIR'] = srcdir
+    task.env['OUTDIR'] = outdir.abspath()
+    task.env['DOCTREEDIR'] = doctreedir
+    task.env['VERSION'] = f'version={self.version}'
+    task.env['RELEASE'] = f'release={release}'
+
+    if buildername == 'man':
+        confdata = load_source('sphinx_conf', conf.abspath())
+        for i in confdata.man_pages:
+            target = outdir.find_or_declare(f'{i[1]}.{i[4]}')
+            task.outputs.append(target)
+            if self.install_path:
+                self.bld.install_files(f'{self.install_path}/man{i[4]}/', target)
+    else:
+        task.outputs.append(outdir)
+
+    # prevent process_source from complaining that there is no extension mapping for .rst files
+    self.source = []
+
+
+def configure(conf):
+    """Check if sphinx-build program is available."""
+    conf.find_program('sphinx-build', var='SPHINX_BUILD', mandatory=False)
+
+
+# sphinx command
+from waflib.Build import BuildContext
+class sphinx(BuildContext):
+    cmd = 'sphinx'
+    fun = 'sphinx'
diff --git a/.waf-tools/sphinx_build.py b/.waf-tools/sphinx_build.py
deleted file mode 100644
index 8585352..0000000
--- a/.waf-tools/sphinx_build.py
+++ /dev/null
@@ -1,76 +0,0 @@
-# inspired by code by Hans-Martin von Gaudecker, 2012
-
-import os
-from waflib import Node, Task, TaskGen, Errors, Logs, Build, Utils
-
-class sphinx_build(Task.Task):
-    color = 'BLUE'
-    run_str = '${SPHINX_BUILD} -D ${VERSION} -D ${RELEASE} -q -b ${BUILDERNAME} -d ${DOCTREEDIR} ${SRCDIR} ${OUTDIR}'
-
-    def __str__(self):
-        env = self.env
-        src_str = ' '.join([a.path_from(a.ctx.launch_node()) for a in self.inputs])
-        tgt_str = ' '.join([a.path_from(a.ctx.launch_node()) for a in self.outputs])
-        if self.outputs: sep = ' -> '
-        else: sep = ''
-        return'%s [%s]: %s%s%s\n'%(self.__class__.__name__.replace('_task',''),
-                                   self.env['BUILDERNAME'], src_str, sep, tgt_str)
-
-@TaskGen.extension('.py', '.rst')
-def sig_hook(self, node):
-    node.sig=Utils.h_file(node.abspath())
-
-@TaskGen.feature("sphinx")
-@TaskGen.before_method("process_source")
-def apply_sphinx(self):
-    """Set up the task generator with a Sphinx instance and create a task."""
-
-    inputs = []
-    for i in Utils.to_list(self.source):
-        if not isinstance(i, Node.Node):
-            node = self.path.find_node(node)
-        else:
-            node = i
-        if not node:
-            raise ValueError('[%s] file not found' % i)
-        inputs.append(node)
-
-    task = self.create_task('sphinx_build', inputs)
-
-    conf = self.path.find_node(self.config)
-    task.inputs.append(conf)
-
-    confdir = conf.parent.abspath()
-    buildername = getattr(self, 'builder', 'html')
-    srcdir = getattr(self, 'srcdir', confdir)
-    outdir = self.path.find_or_declare(getattr(self, 'outdir', buildername)).get_bld()
-    doctreedir = getattr(self, 'doctreedir', os.path.join(outdir.abspath(), '.doctrees'))
-
-    task.env['BUILDERNAME'] = buildername
-    task.env['SRCDIR'] = srcdir
-    task.env['DOCTREEDIR'] = doctreedir
-    task.env['OUTDIR'] = outdir.abspath()
-    task.env['VERSION'] = 'version=%s' % self.version
-    task.env['RELEASE'] = 'release=%s' % getattr(self, 'release', self.version)
-
-    import imp
-    confData = imp.load_source('sphinx_conf', conf.abspath())
-
-    if buildername == 'man':
-        for i in confData.man_pages:
-            target = outdir.find_or_declare('%s.%d' % (i[1], i[4]))
-            task.outputs.append(target)
-
-            if self.install_path:
-                self.bld.install_files('%s/man%d/' % (self.install_path, i[4]), target)
-    else:
-        task.outputs.append(outdir)
-
-def configure(conf):
-    conf.find_program('sphinx-build', var='SPHINX_BUILD', mandatory=False)
-
-# sphinx docs
-from waflib.Build import BuildContext
-class sphinx(BuildContext):
-    cmd = "sphinx"
-    fun = "sphinx"