cmake: switch to pathlib (fixes #7322)

9 files changed, 260 insertions, 252 deletions

diff --git a/mesonbuild/cmake/client.py b/mesonbuild/cmake/client.py
index 2089be4..8057c3b 100644
--- a/mesonbuild/cmake/client.py
+++ b/mesonbuild/cmake/client.py
@@ -21,9 +21,9 @@ from ..mesonlib import MachineChoice
 from .. import mlog
 from contextlib import contextmanager
 from subprocess import Popen, PIPE, TimeoutExpired
+from pathlib import Path
 import typing as T
 import json
-import os
 
 if T.TYPE_CHECKING:
     from ..environment import Environment
@@ -128,7 +128,7 @@ class MessageHello(MessageBase):
 # Request classes
 
 class RequestHandShake(RequestBase):
-    def __init__(self, src_dir: str, build_dir: str, generator: str, vers_major: int, vers_minor: T.Optional[int] = None) -> None:
+    def __init__(self, src_dir: Path, build_dir: Path, generator: str, vers_major: int, vers_minor: T.Optional[int] = None) -> None:
         super().__init__('handshake')
         self.src_dir = src_dir
         self.build_dir = build_dir
@@ -142,13 +142,13 @@ class RequestHandShake(RequestBase):
             vers['minor'] = self.vers_minor
 
         # Old CMake versions (3.7) want '/' even on Windows
-        src_list = os.path.normpath(self.src_dir).split(os.sep)
-        bld_list = os.path.normpath(self.build_dir).split(os.sep)
+        self.src_dir   = self.src_dir.resolve()
+        self.build_dir = self.build_dir.resolve()
 
         return {
             **super().to_dict(),
-            'sourceDirectory': '/'.join(src_list),
-            'buildDirectory': '/'.join(bld_list),
+            'sourceDirectory': self.src_dir.as_posix(),
+            'buildDirectory': self.build_dir.as_posix(),
             'generator': self.generator,
             'protocolVersion': vers
         }
@@ -191,15 +191,15 @@ class ReplyCompute(ReplyBase):
         super().__init__(cookie, 'compute')
 
 class ReplyCMakeInputs(ReplyBase):
-    def __init__(self, cookie: str, cmake_root: str, src_dir: str, build_files: T.List[CMakeBuildFile]) -> None:
+    def __init__(self, cookie: str, cmake_root: Path, src_dir: Path, build_files: T.List[CMakeBuildFile]) -> None:
         super().__init__(cookie, 'cmakeInputs')
         self.cmake_root = cmake_root
         self.src_dir = src_dir
         self.build_files = build_files
 
     def log(self) -> None:
-        mlog.log('CMake root: ', mlog.bold(self.cmake_root))
-        mlog.log('Source dir: ', mlog.bold(self.src_dir))
+        mlog.log('CMake root: ', mlog.bold(self.cmake_root.as_posix()))
+        mlog.log('Source dir: ', mlog.bold(self.src_dir.as_posix()))
         mlog.log('Build files:', mlog.bold(str(len(self.build_files))))
         with mlog.nested():
             for i in self.build_files:
@@ -304,7 +304,7 @@ class CMakeClient:
             raise CMakeException('CMake server query failed')
         return reply
 
-    def do_handshake(self, src_dir: str, build_dir: str, generator: str, vers_major: int, vers_minor: T.Optional[int] = None) -> None:
+    def do_handshake(self, src_dir: Path, build_dir: Path, generator: str, vers_major: int, vers_minor: T.Optional[int] = None) -> None:
         # CMake prints the hello message on startup
         msg = self.readMessage()
         if not isinstance(msg, MessageHello):
@@ -327,8 +327,8 @@ class CMakeClient:
         files = []
         for i in data['buildFiles']:
             for j in i['sources']:
-                files += [CMakeBuildFile(j, i['isCMake'], i['isTemporary'])]
-        return ReplyCMakeInputs(data['cookie'], data['cmakeRootDirectory'], data['sourceDirectory'], files)
+                files += [CMakeBuildFile(Path(j), i['isCMake'], i['isTemporary'])]
+        return ReplyCMakeInputs(data['cookie'], Path(data['cmakeRootDirectory']), Path(data['sourceDirectory']), files)
 
     @contextmanager
     def connect(self) -> T.Generator[None, None, None]:
diff --git a/mesonbuild/cmake/common.py b/mesonbuild/cmake/common.py
index f6bd944..bb0c4ae 100644
--- a/mesonbuild/cmake/common.py
+++ b/mesonbuild/cmake/common.py
@@ -17,13 +17,14 @@
 
 from ..mesonlib import MesonException
 from .. import mlog
+from pathlib import Path
 import typing as T
 
 class CMakeException(MesonException):
     pass
 
 class CMakeBuildFile:
-    def __init__(self, file: str, is_cmake: bool, is_temp: bool) -> None:
+    def __init__(self, file: Path, is_cmake: bool, is_temp: bool) -> None:
         self.file = file
         self.is_cmake = is_cmake
         self.is_temp = is_temp
@@ -81,7 +82,7 @@ def cmake_defines_to_args(raw: T.Any, permissive: bool = False) -> T.List[str]:
     return res
 
 class CMakeInclude:
-    def __init__(self, path: str, isSystem: bool = False):
+    def __init__(self, path: Path, isSystem: bool = False):
         self.path     = path
         self.isSystem = isSystem
 
@@ -94,7 +95,7 @@ class CMakeFileGroup:
         self.flags        = _flags_to_list(data.get('compileFlags', ''))  # type: T.List[str]
         self.is_generated = data.get('isGenerated', False)                # type: bool
         self.language     = data.get('language', 'C')                     # type: str
-        self.sources      = data.get('sources', [])                       # type: T.List[str]
+        self.sources      = [Path(x) for x in data.get('sources', [])]    # type: T.List[Path]
 
         # Fix the include directories
         self.includes = []  # type: T.List[CMakeInclude]
@@ -103,9 +104,9 @@ class CMakeFileGroup:
                 isSystem = i.get('isSystem', False)
                 assert isinstance(isSystem, bool)
                 assert isinstance(i['path'], str)
-                self.includes += [CMakeInclude(i['path'], isSystem)]
+                self.includes += [CMakeInclude(Path(i['path']), isSystem)]
             elif isinstance(i, str):
-                self.includes += [CMakeInclude(i)]
+                self.includes += [CMakeInclude(Path(i))]
 
     def log(self) -> None:
         mlog.log('flags        =', mlog.bold(', '.join(self.flags)))
@@ -116,22 +117,22 @@ class CMakeFileGroup:
         mlog.log('sources:')
         for i in self.sources:
             with mlog.nested():
-                mlog.log(i)
+                mlog.log(i.as_posix())
 
 class CMakeTarget:
     def __init__(self, data: T.Dict[str, T.Any]) -> None:
-        self.artifacts               = data.get('artifacts', [])                            # type: T.List[str]
-        self.src_dir                 = data.get('sourceDirectory', '')                      # type: str
-        self.build_dir               = data.get('buildDirectory', '')                       # type: str
+        self.artifacts               = [Path(x) for x in data.get('artifacts', [])]         # type: T.List[Path]
+        self.src_dir                 = Path(data.get('sourceDirectory', ''))                # type: Path
+        self.build_dir               = Path(data.get('buildDirectory', ''))                 # type: Path
         self.name                    = data.get('name', '')                                 # type: str
         self.full_name               = data.get('fullName', '')                             # type: str
         self.install                 = data.get('hasInstallRule', False)                    # type: bool
-        self.install_paths           = list(set(data.get('installPaths', [])))              # type: T.List[str]
+        self.install_paths           = [Path(x) for x in set(data.get('installPaths', []))] # type: T.List[Path]
         self.link_lang               = data.get('linkerLanguage', '')                       # type: str
         self.link_libraries          = _flags_to_list(data.get('linkLibraries', ''))        # type: T.List[str]
         self.link_flags              = _flags_to_list(data.get('linkFlags', ''))            # type: T.List[str]
         self.link_lang_flags         = _flags_to_list(data.get('linkLanguageFlags', ''))    # type: T.List[str]
-        # self.link_path             = data.get('linkPath', '')                             # type: str
+        # self.link_path             = Path(data.get('linkPath', ''))                       # type: Path
         self.type                    = data.get('type', 'EXECUTABLE')                       # type: str
         # self.is_generator_provided = data.get('isGeneratorProvided', False)               # type: bool
         self.files                   = []                                                   # type: T.List[CMakeFileGroup]
@@ -140,13 +141,13 @@ class CMakeTarget:
             self.files += [CMakeFileGroup(i)]
 
     def log(self) -> None:
-        mlog.log('artifacts             =', mlog.bold(', '.join(self.artifacts)))
-        mlog.log('src_dir               =', mlog.bold(self.src_dir))
-        mlog.log('build_dir             =', mlog.bold(self.build_dir))
+        mlog.log('artifacts             =', mlog.bold(', '.join([x.as_posix() for x in self.artifacts])))
+        mlog.log('src_dir               =', mlog.bold(self.src_dir.as_posix()))
+        mlog.log('build_dir             =', mlog.bold(self.build_dir.as_posix()))
         mlog.log('name                  =', mlog.bold(self.name))
         mlog.log('full_name             =', mlog.bold(self.full_name))
         mlog.log('install               =', mlog.bold('true' if self.install else 'false'))
-        mlog.log('install_paths         =', mlog.bold(', '.join(self.install_paths)))
+        mlog.log('install_paths         =', mlog.bold(', '.join([x.as_posix() for x in self.install_paths])))
         mlog.log('link_lang             =', mlog.bold(self.link_lang))
         mlog.log('link_libraries        =', mlog.bold(', '.join(self.link_libraries)))
         mlog.log('link_flags            =', mlog.bold(', '.join(self.link_flags)))
@@ -161,17 +162,17 @@ class CMakeTarget:
 
 class CMakeProject:
     def __init__(self, data: T.Dict[str, T.Any]) -> None:
-        self.src_dir   = data.get('sourceDirectory', '')   # type: str
-        self.build_dir = data.get('buildDirectory', '')    # type: str
-        self.name      = data.get('name', '')              # type: str
-        self.targets   = []                                # type: T.List[CMakeTarget]
+        self.src_dir   = Path(data.get('sourceDirectory', ''))   # type: Path
+        self.build_dir = Path(data.get('buildDirectory', ''))    # type: Path
+        self.name      = data.get('name', '')                    # type: str
+        self.targets   = []                                      # type: T.List[CMakeTarget]
 
         for i in data.get('targets', []):
             self.targets += [CMakeTarget(i)]
 
     def log(self) -> None:
-        mlog.log('src_dir   =', mlog.bold(self.src_dir))
-        mlog.log('build_dir =', mlog.bold(self.build_dir))
+        mlog.log('src_dir   =', mlog.bold(self.src_dir.as_posix()))
+        mlog.log('build_dir =', mlog.bold(self.build_dir.as_posix()))
         mlog.log('name      =', mlog.bold(self.name))
         for idx, i in enumerate(self.targets):
             mlog.log('Target {}:'.format(idx))
diff --git a/mesonbuild/cmake/executor.py b/mesonbuild/cmake/executor.py
index d3588f0..bf89822 100644
--- a/mesonbuild/cmake/executor.py
+++ b/mesonbuild/cmake/executor.py
@@ -189,14 +189,14 @@ class CMakeExecutor:
         if always_capture_stderr is not None:
             self.always_capture_stderr = always_capture_stderr
 
-    def _cache_key(self, args: T.List[str], build_dir: str, env: T.Optional[T.Dict[str, str]]) -> TYPE_cache_key:
+    def _cache_key(self, args: T.List[str], build_dir: Path, env: T.Optional[T.Dict[str, str]]) -> TYPE_cache_key:
         fenv = frozenset(env.items()) if env is not None else frozenset()
         targs = tuple(args)
-        return (self.cmakebin.get_path(), targs, build_dir, fenv)
+        return (self.cmakebin.get_path(), targs, build_dir.as_posix(), fenv)
 
-    def _call_cmout_stderr(self, args: T.List[str], build_dir: str, env: T.Optional[T.Dict[str, str]]) -> TYPE_result:
+    def _call_cmout_stderr(self, args: T.List[str], build_dir: Path, env: T.Optional[T.Dict[str, str]]) -> TYPE_result:
         cmd = self.cmakebin.get_command() + args
-        proc = S.Popen(cmd, stdout=S.PIPE, stderr=S.PIPE, cwd=build_dir, env=env)
+        proc = S.Popen(cmd, stdout=S.PIPE, stderr=S.PIPE, cwd=str(build_dir), env=env)  # TODO [PYTHON_37]: drop Path conversion
 
         # stdout and stderr MUST be read at the same time to avoid pipe
         # blocking issues. The easiest way to do this is with a separate
@@ -237,9 +237,9 @@ class CMakeExecutor:
 
         return proc.returncode, None, raw_trace
 
-    def _call_cmout(self, args: T.List[str], build_dir: str, env: T.Optional[T.Dict[str, str]]) -> TYPE_result:
+    def _call_cmout(self, args: T.List[str], build_dir: Path, env: T.Optional[T.Dict[str, str]]) -> TYPE_result:
         cmd = self.cmakebin.get_command() + args
-        proc = S.Popen(cmd, stdout=S.PIPE, stderr=S.STDOUT, cwd=build_dir, env=env)
+        proc = S.Popen(cmd, stdout=S.PIPE, stderr=S.STDOUT, cwd=str(build_dir), env=env)  # TODO [PYTHON_37]: drop Path conversion
         while True:
             line = proc.stdout.readline()
             if not line:
@@ -249,11 +249,11 @@ class CMakeExecutor:
         proc.wait()
         return proc.returncode, None, None
 
-    def _call_quiet(self, args: T.List[str], build_dir: str, env: T.Optional[T.Dict[str, str]]) -> TYPE_result:
-        os.makedirs(build_dir, exist_ok=True)
+    def _call_quiet(self, args: T.List[str], build_dir: Path, env: T.Optional[T.Dict[str, str]]) -> TYPE_result:
+        build_dir.mkdir(parents=True, exist_ok=True)
         cmd = self.cmakebin.get_command() + args
-        ret = S.run(cmd, env=env, cwd=build_dir, close_fds=False,
-                    stdout=S.PIPE, stderr=S.PIPE, universal_newlines=False)
+        ret = S.run(cmd, env=env, cwd=str(build_dir), close_fds=False,
+                    stdout=S.PIPE, stderr=S.PIPE, universal_newlines=False)   # TODO [PYTHON_37]: drop Path conversion
         rc = ret.returncode
         out = ret.stdout.decode(errors='ignore')
         err = ret.stderr.decode(errors='ignore')
@@ -261,7 +261,7 @@ class CMakeExecutor:
         mlog.debug("Called `{}` in {} -> {}".format(call, build_dir, rc))
         return rc, out, err
 
-    def _call_impl(self, args: T.List[str], build_dir: str, env: T.Optional[T.Dict[str, str]]) -> TYPE_result:
+    def _call_impl(self, args: T.List[str], build_dir: Path, env: T.Optional[T.Dict[str, str]]) -> TYPE_result:
         if not self.print_cmout:
             return self._call_quiet(args, build_dir, env)
         else:
@@ -270,7 +270,7 @@ class CMakeExecutor:
             else:
                 return self._call_cmout(args, build_dir, env)
 
-    def call(self, args: T.List[str], build_dir: str, env: T.Optional[T.Dict[str, str]] = None, disable_cache: bool = False) -> TYPE_result:
+    def call(self, args: T.List[str], build_dir: Path, env: T.Optional[T.Dict[str, str]] = None, disable_cache: bool = False) -> TYPE_result:
         if env is None:
             env = os.environ.copy()
 
@@ -285,28 +285,28 @@ class CMakeExecutor:
             cache[key] = self._call_impl(args, build_dir, env)
         return cache[key]
 
-    def call_with_fake_build(self, args: T.List[str], build_dir: str, env: T.Optional[T.Dict[str, str]] = None) -> TYPE_result:
+    def call_with_fake_build(self, args: T.List[str], build_dir: Path, env: T.Optional[T.Dict[str, str]] = None) -> TYPE_result:
         # First check the cache
         cache = CMakeExecutor.class_cmake_cache
         key = self._cache_key(args, build_dir, env)
         if key in cache:
             return cache[key]
 
-        os.makedirs(build_dir, exist_ok=True)
+        build_dir.mkdir(exist_ok=True, parents=True)
 
         # Try to set the correct compiler for C and C++
         # This step is required to make try_compile work inside CMake
-        fallback = os.path.realpath(__file__)  # A file used as a fallback wehen everything else fails
+        fallback = Path(__file__).resolve()  # A file used as a fallback wehen everything else fails
         compilers = self.environment.coredata.compilers[MachineChoice.BUILD]
 
         def make_abs(exe: str, lang: str) -> str:
-            if os.path.isabs(exe):
+            if Path(exe).is_absolute():
                 return exe
 
             p = shutil.which(exe)
             if p is None:
                 mlog.debug('Failed to find a {} compiler for CMake. This might cause CMake to fail.'.format(lang))
-                p = fallback
+                return str(fallback)
             return p
 
         def choose_compiler(lang: str) -> T.Tuple[str, str, str, str]:
@@ -331,7 +331,7 @@ class CMakeExecutor:
                 return make_abs(exe_list[1], lang), make_abs(exe_list[0], lang), comp_id, comp_version
             else:
                 mlog.debug('Failed to find a {} compiler for CMake. This might cause CMake to fail.'.format(lang))
-                return fallback, '', 'GNU', ''
+                return str(fallback), '', 'GNU', ''
 
         c_comp, c_launcher, c_id, c_version = choose_compiler('c')
         cxx_comp, cxx_launcher, cxx_id, cxx_version = choose_compiler('cpp')
@@ -346,10 +346,10 @@ class CMakeExecutor:
         fortran_launcher = fortran_launcher.replace('\\', '/')
 
         # Reset the CMake cache
-        (Path(build_dir) / 'CMakeCache.txt').write_text('CMAKE_PLATFORM_INFO_INITIALIZED:INTERNAL=1\n')
+        (build_dir / 'CMakeCache.txt').write_text('CMAKE_PLATFORM_INFO_INITIALIZED:INTERNAL=1\n')
 
         # Fake the compiler files
-        comp_dir = Path(build_dir) / 'CMakeFiles' / self.cmakevers
+        comp_dir = build_dir / 'CMakeFiles' / self.cmakevers
         comp_dir.mkdir(parents=True, exist_ok=True)
 
         c_comp_file = comp_dir / 'CMakeCCompiler.cmake'
diff --git a/mesonbuild/cmake/fileapi.py b/mesonbuild/cmake/fileapi.py
index 0405145..4ef0caf 100644
--- a/mesonbuild/cmake/fileapi.py
+++ b/mesonbuild/cmake/fileapi.py
@@ -15,21 +15,21 @@
 from .common import CMakeException, CMakeBuildFile, CMakeConfiguration
 import typing as T
 from .. import mlog
-import os
+from pathlib import Path
 import json
 import re
 
 STRIP_KEYS = ['cmake', 'reply', 'backtrace', 'backtraceGraph', 'version']
 
 class CMakeFileAPI:
-    def __init__(self, build_dir: str):
-        self.build_dir = build_dir
-        self.api_base_dir = os.path.join(self.build_dir, '.cmake', 'api', 'v1')
-        self.request_dir = os.path.join(self.api_base_dir, 'query', 'client-meson')
-        self.reply_dir = os.path.join(self.api_base_dir, 'reply')
-        self.cmake_sources = []          # type: T.List[CMakeBuildFile]
+    def __init__(self, build_dir: Path):
+        self.build_dir            = build_dir
+        self.api_base_dir         = self.build_dir / '.cmake' / 'api' / 'v1'
+        self.request_dir          = self.api_base_dir / 'query' / 'client-meson'
+        self.reply_dir            = self.api_base_dir / 'reply'
+        self.cmake_sources        = []   # type: T.List[CMakeBuildFile]
         self.cmake_configurations = []   # type: T.List[CMakeConfiguration]
-        self.kind_resolver_map = {
+        self.kind_resolver_map    = {
             'codemodel': self._parse_codemodel,
             'cmakeFiles': self._parse_cmakeFiles,
         }
@@ -41,7 +41,7 @@ class CMakeFileAPI:
         return self.cmake_configurations
 
     def setup_request(self) -> None:
-        os.makedirs(self.request_dir, exist_ok=True)
+        self.request_dir.mkdir(parents=True, exist_ok=True)
 
         query = {
             'requests': [
@@ -50,18 +50,17 @@ class CMakeFileAPI:
             ]
         }
 
-        with open(os.path.join(self.request_dir, 'query.json'), 'w') as fp:
-            json.dump(query, fp, indent=2)
+        query_file = self.request_dir / 'query.json'
+        query_file.write_text(json.dumps(query, indent=2))
 
     def load_reply(self) -> None:
-        if not os.path.isdir(self.reply_dir):
+        if not self.reply_dir.is_dir():
             raise CMakeException('No response from the CMake file API')
 
-        files = os.listdir(self.reply_dir)
         root = None
         reg_index = re.compile(r'^index-.*\.json$')
-        for i in files:
-            if reg_index.match(i):
+        for i in self.reply_dir.iterdir():
+            if reg_index.match(i.name):
                 root = i
                 break
 
@@ -74,10 +73,9 @@ class CMakeFileAPI:
         index = self._strip_data(index)          # Strip unused data (again for loaded files)
 
         # Debug output
-        debug_json = os.path.normpath(os.path.join(self.build_dir, '..', 'fileAPI.json'))
-        with open(debug_json, 'w') as fp:
-            json.dump(index, fp, indent=2)
-        mlog.cmd_ci_include(debug_json)
+        debug_json = self.build_dir / '..' / 'fileAPI.json'
+        debug_json.write_text(json.dumps(index, indent=2))
+        mlog.cmd_ci_include(debug_json.as_posix())
 
         # parse the JSON
         for i in index['objects']:
@@ -100,17 +98,17 @@ class CMakeFileAPI:
         # resolved and the resulting data structure is identical
         # to the CMake serve output.
 
-        def helper_parse_dir(dir_entry: T.Dict[str, T.Any]) -> T.Tuple[str, str]:
-            src_dir = dir_entry.get('source', '.')
-            bld_dir = dir_entry.get('build', '.')
-            src_dir = src_dir if os.path.isabs(src_dir) else os.path.join(source_dir, src_dir)
-            bld_dir = bld_dir if os.path.isabs(bld_dir) else os.path.join(source_dir, bld_dir)
-            src_dir = os.path.normpath(src_dir)
-            bld_dir = os.path.normpath(bld_dir)
+        def helper_parse_dir(dir_entry: T.Dict[str, T.Any]) -> T.Tuple[Path, Path]:
+            src_dir = Path(dir_entry.get('source', '.'))
+            bld_dir = Path(dir_entry.get('build', '.'))
+            src_dir = src_dir if src_dir.is_absolute() else source_dir / src_dir
+            bld_dir = bld_dir if bld_dir.is_absolute() else build_dir  / bld_dir
+            src_dir = src_dir.resolve()
+            bld_dir = bld_dir.resolve()
 
             return src_dir, bld_dir
 
-        def parse_sources(comp_group: T.Dict[str, T.Any], tgt: T.Dict[str, T.Any]) -> T.Tuple[T.List[str], T.List[str], T.List[int]]:
+        def parse_sources(comp_group: T.Dict[str, T.Any], tgt: T.Dict[str, T.Any]) -> T.Tuple[T.List[Path], T.List[Path], T.List[int]]:
             gen = []
             src = []
             idx = []
@@ -120,9 +118,9 @@ class CMakeFileAPI:
                 if i >= len(src_list_raw) or 'path' not in src_list_raw[i]:
                     continue
                 if src_list_raw[i].get('isGenerated', False):
-                    gen += [src_list_raw[i]['path']]
+                    gen += [Path(src_list_raw[i]['path'])]
                 else:
-                    src += [src_list_raw[i]['path']]
+                    src += [Path(src_list_raw[i]['path'])]
                 idx += [i]
 
             return src, gen, idx
@@ -133,8 +131,8 @@ class CMakeFileAPI:
             # Parse install paths (if present)
             install_paths = []
             if 'install' in tgt:
-                prefix = tgt['install']['prefix']['path']
-                install_paths = [os.path.join(prefix, x['path']) for x in tgt['install']['destinations']]
+                prefix = Path(tgt['install']['prefix']['path'])
+                install_paths = [prefix / x['path'] for x in tgt['install']['destinations']]
                 install_paths = list(set(install_paths))
 
             # On the first look, it looks really nice that the CMake devs have
@@ -160,7 +158,7 @@ class CMakeFileAPI:
             #      maybe we can make use of that in addition to the
             #      implicit dependency detection
             tgt_data = {
-                'artifacts': [x.get('path', '') for x in tgt.get('artifacts', [])],
+                'artifacts': [Path(x.get('path', '')) for x in tgt.get('artifacts', [])],
                 'sourceDirectory': src_dir,
                 'buildDirectory': bld_dir,
                 'name': tgt.get('name', ''),
@@ -269,14 +267,14 @@ class CMakeFileAPI:
             self.cmake_configurations += [CMakeConfiguration(cnf_data)]
 
     def _parse_cmakeFiles(self, data: T.Dict[str, T.Any]) -> None:
-        assert('inputs' in data)
-        assert('paths' in data)
+        assert 'inputs' in data
+        assert 'paths' in data
 
-        src_dir = data['paths']['source']
+        src_dir = Path(data['paths']['source'])
 
         for i in data['inputs']:
-            path = i['path']
-            path = path if os.path.isabs(path) else os.path.join(src_dir, path)
+            path = Path(i['path'])
+            path = path if path.is_absolute() else src_dir / path
             self.cmake_sources += [CMakeBuildFile(path, i.get('isCMake', False), i.get('isGenerated', False))]
 
     def _strip_data(self, data: T.Any) -> T.Any:
@@ -309,14 +307,13 @@ class CMakeFileAPI:
 
         return data
 
-    def _reply_file_content(self, filename: str) -> T.Dict[str, T.Any]:
-        real_path = os.path.join(self.reply_dir, filename)
-        if not os.path.exists(real_path):
+    def _reply_file_content(self, filename: Path) -> T.Dict[str, T.Any]:
+        real_path = self.reply_dir / filename
+        if not real_path.exists():
             raise CMakeException('File "{}" does not exist'.format(real_path))
 
-        with open(real_path, 'r') as fp:
-            data = json.load(fp)
-            assert isinstance(data, dict)
-            for i in data.keys():
-                assert isinstance(i, str)
-            return data
+        data = json.loads(real_path.read_text())
+        assert isinstance(data, dict)
+        for i in data.keys():
+            assert isinstance(i, str)
+        return data
diff --git a/mesonbuild/cmake/interpreter.py b/mesonbuild/cmake/interpreter.py
index 1a7fe7a..aa43ae4 100644
--- a/mesonbuild/cmake/interpreter.py
+++ b/mesonbuild/cmake/interpreter.py
@@ -21,14 +21,15 @@ from .fileapi import CMakeFileAPI
 from .executor import CMakeExecutor
 from .traceparser import CMakeTraceParser, CMakeGeneratorTarget
 from .. import mlog, mesonlib
-from ..mesonlib import MachineChoice, OrderedSet, version_compare
+from ..mesonlib import MachineChoice, OrderedSet, version_compare, path_is_in_root, relative_to_if_possible
 from ..mesondata import mesondata
 from ..compilers.compilers import lang_suffixes, header_suffixes, obj_suffixes, lib_suffixes, is_header
 from enum import Enum
 from functools import lru_cache
 from pathlib import Path
 import typing as T
-import os, re
+import re
+from os import environ
 
 from ..mparser import (
     Token,
@@ -52,7 +53,7 @@ if T.TYPE_CHECKING:
     from ..backend.backends import Backend
     from ..environment import Environment
 
-TYPE_mixed        = T.Union[str, int, bool, BaseNode]
+TYPE_mixed        = T.Union[str, int, bool, Path, BaseNode]
 TYPE_mixed_list   = T.Union[TYPE_mixed, T.Sequence[TYPE_mixed]]
 TYPE_mixed_kwargs = T.Dict[str, TYPE_mixed_list]
 
@@ -141,7 +142,7 @@ def _sanitize_cmake_name(name: str) -> str:
 class OutputTargetMap:
     rm_so_version = re.compile(r'(\.[0-9]+)+$')
 
-    def __init__(self, build_dir: str):
+    def __init__(self, build_dir: Path):
         self.tgt_map   = {}          # type: T.Dict[str, T.Union['ConverterTarget', 'ConverterCustomTarget']]
         self.build_dir = build_dir
 
@@ -186,37 +187,38 @@ class OutputTargetMap:
             new_name = OutputTargetMap.rm_so_version.sub('', new_name)
             candidates += ['{}.{}'.format(new_name, i)]
         for i in candidates:
-            keys += [self._rel_artifact_key(i), os.path.basename(i), self._base_artifact_key(i)]
+            keys += [self._rel_artifact_key(Path(i)), Path(i).name, self._base_artifact_key(Path(i))]
         return self._return_first_valid_key(keys)
 
-    def generated(self, name: str) -> T.Optional['ConverterCustomTarget']:
+    def generated(self, name: Path) -> T.Optional['ConverterCustomTarget']:
         res = self._return_first_valid_key([self._rel_generated_file_key(name), self._base_generated_file_key(name)])
         assert res is None or isinstance(res, ConverterCustomTarget)
         return res
 
     # Utility functions to generate local keys
-    def _rel_path(self, fname: str) -> T.Optional[str]:
-        fname = os.path.normpath(os.path.join(self.build_dir, fname))
-        if os.path.commonpath([self.build_dir, fname]) != self.build_dir:
-            return None
-        return os.path.relpath(fname, self.build_dir)
+    def _rel_path(self, fname: Path) -> T.Optional[Path]:
+        try:
+            return fname.resolve().relative_to(self.build_dir)
+        except ValueError:
+            pass
+        return None
 
     def _target_key(self, tgt_name: str) -> str:
         return '__tgt_{}__'.format(tgt_name)
 
-    def _rel_generated_file_key(self, fname: str) -> T.Optional[str]:
+    def _rel_generated_file_key(self, fname: Path) -> T.Optional[str]:
         path = self._rel_path(fname)
-        return '__relgen_{}__'.format(path) if path else None
+        return '__relgen_{}__'.format(path.as_posix()) if path else None
 
-    def _base_generated_file_key(self, fname: str) -> str:
-        return '__gen_{}__'.format(os.path.basename(fname))
+    def _base_generated_file_key(self, fname: Path) -> str:
+        return '__gen_{}__'.format(fname.name)
 
-    def _rel_artifact_key(self, fname: str) -> T.Optional[str]:
+    def _rel_artifact_key(self, fname: Path) -> T.Optional[str]:
         path = self._rel_path(fname)
-        return '__relart_{}__'.format(path) if path else None
+        return '__relart_{}__'.format(path.as_posix()) if path else None
 
-    def _base_artifact_key(self, fname: str) -> str:
-        return '__art_{}__'.format(os.path.basename(fname))
+    def _base_artifact_key(self, fname: Path) -> str:
+        return '__art_{}__'.format(fname.name)
 
 class ConverterTarget:
     def __init__(self, target: CMakeTarget, env: 'Environment') -> None:
@@ -229,7 +231,7 @@ class ConverterTarget:
         self.full_name      = target.full_name
         self.type           = target.type
         self.install        = target.install
-        self.install_dir    = ''
+        self.install_dir    = None  # type: T.Optional[Path]
         self.link_libraries = target.link_libraries
         self.link_flags     = target.link_flags + target.link_lang_flags
         self.depends_raw    = []  # type: T.List[str]
@@ -239,11 +241,11 @@ class ConverterTarget:
             self.install_dir = target.install_paths[0]
 
         self.languages           = []  # type: T.List[str]
-        self.sources             = []  # type: T.List[str]
-        self.generated           = []  # type: T.List[str]
+        self.sources             = []  # type: T.List[Path]
+        self.generated           = []  # type: T.List[Path]
         self.generated_ctgt      = []  # type: T.List[CustomTargetReference]
-        self.includes            = []  # type: T.List[str]
-        self.sys_includes        = []  # type: T.List[str]
+        self.includes            = []  # type: T.List[Path]
+        self.sys_includes        = []  # type: T.List[Path]
         self.link_with           = []  # type: T.List[T.Union[ConverterTarget, ConverterCustomTarget]]
         self.object_libs         = []  # type: T.List[ConverterTarget]
         self.compile_opts        = {}  # type: T.Dict[str, T.List[str]]
@@ -256,7 +258,7 @@ class ConverterTarget:
         # Convert the target name to a valid meson target name
         self.name = _sanitize_cmake_name(self.name)
 
-        self.generated_raw = []  # type: T.List[str]
+        self.generated_raw = []  # type: T.List[Path]
         for i in target.files:
             # Determine the meson language
             lang_cmake_to_meson = {val.lower(): key for key, val in language_map.items()}
@@ -286,7 +288,7 @@ class ConverterTarget:
 
     std_regex = re.compile(r'([-]{1,2}std=|/std:v?|[-]{1,2}std:)(.*)')
 
-    def postprocess(self, output_target_map: OutputTargetMap, root_src_dir: str, subdir: str, install_prefix: str, trace: CMakeTraceParser) -> None:
+    def postprocess(self, output_target_map: OutputTargetMap, root_src_dir: Path, subdir: Path, install_prefix: Path, trace: CMakeTraceParser) -> None:
         # Detect setting the C and C++ standard and do additional compiler args manipulation
         for i in ['c', 'cpp']:
             if i not in self.compile_opts:
@@ -295,7 +297,7 @@ class ConverterTarget:
             temp = []
             for j in self.compile_opts[i]:
                 m = ConverterTarget.std_regex.match(j)
-                ctgt = output_target_map.generated(j)
+                ctgt = output_target_map.generated(Path(j))
                 if m:
                     std = m.group(2)
                     supported = self._all_lang_stds(i)
@@ -314,7 +316,7 @@ class ConverterTarget:
                     # Sometimes projects pass generated source files as compiler
                     # flags. Add these as generated sources to ensure that the
                     # corresponding custom target is run.2
-                    self.generated_raw += [j]
+                    self.generated_raw += [Path(j)]
                     temp += [j]
                 elif j in blacklist_compiler_flags:
                     pass
@@ -350,7 +352,7 @@ class ConverterTarget:
                 mlog.debug(str(tgt))
 
                 if 'INTERFACE_INCLUDE_DIRECTORIES' in tgt.properties:
-                    self.includes += [x for x in tgt.properties['INTERFACE_INCLUDE_DIRECTORIES'] if x]
+                    self.includes += [Path(x) for x in tgt.properties['INTERFACE_INCLUDE_DIRECTORIES'] if x]
 
                 if 'INTERFACE_LINK_OPTIONS' in tgt.properties:
                     self.link_flags += [x for x in tgt.properties['INTERFACE_LINK_OPTIONS'] if x]
@@ -402,7 +404,7 @@ class ConverterTarget:
                 for j in otherDeps:
                     if j in trace.targets:
                         to_process += [j]
-                    elif reg_is_lib.match(j) or os.path.exists(j):
+                    elif reg_is_lib.match(j) or Path(j).exists():
                         libraries += [j]
 
                 for j in libraries:
@@ -418,7 +420,7 @@ class ConverterTarget:
             # Let meson handle this arcane magic
             if ',-rpath,' in i:
                 continue
-            if not os.path.isabs(i):
+            if not Path(i).is_absolute():
                 link_with = output_target_map.artifact(i)
                 if link_with:
                     self.link_with += [link_with]
@@ -432,48 +434,45 @@ class ConverterTarget:
         for i in self.languages:
             supported += list(lang_suffixes[i])
         supported = ['.{}'.format(x) for x in supported]
-        self.sources       = [x for x in self.sources       if any([x.endswith(y) for y in supported])]
-        self.generated_raw = [x for x in self.generated_raw if any([x.endswith(y) for y in supported])]
+        self.sources       = [x for x in self.sources       if any([x.name.endswith(y) for y in supported])]
+        self.generated_raw = [x for x in self.generated_raw if any([x.name.endswith(y) for y in supported])]
 
         # Make paths relative
-        def rel_path(x: str, is_header: bool, is_generated: bool) -> T.Optional[str]:
-            if not os.path.isabs(x):
-                x = os.path.join(self.src_dir, x)
-            x = os.path.normpath(x)
-            if not os.path.exists(x) and not any([x.endswith(y) for y in obj_suffixes]) and not is_generated:
+        def rel_path(x: Path, is_header: bool, is_generated: bool) -> T.Optional[Path]:
+            if not x.is_absolute():
+                x = self.src_dir / x
+            x = x.resolve()
+            assert x.is_absolute()
+            if not x.exists() and not any([x.name.endswith(y) for y in obj_suffixes]) and not is_generated:
                 if (
-                    any([os.path.commonpath([x, os.path.normpath(os.path.join(root_src_dir, y))]) == x for y in self.generated_raw])
-                        and os.path.commonpath([x, self.env.get_build_dir()]) == self.env.get_build_dir()
+                    any([path_is_in_root(root_src_dir / y, x.resolve(), resolve=True) for y in self.generated_raw])
+                        and path_is_in_root(x, Path(self.env.get_build_dir()), resolve=True)
                     ):
-                    os.makedirs(x)
-                    return os.path.relpath(x, os.path.join(self.env.get_build_dir(), subdir))
+                    x.mkdir(parents=True, exist_ok=True)
+                    return x.relative_to(Path(self.env.get_build_dir()) / subdir)
                 else:
-                    mlog.warning('CMake: path', mlog.bold(x), 'does not exist.')
+                    mlog.warning('CMake: path', mlog.bold(x.as_posix()), 'does not exist.')
                     mlog.warning(' --> Ignoring. This can lead to build errors.')
                     return None
-            if Path(x) in trace.explicit_headers:
+            if x in trace.explicit_headers:
                 return None
             if (
-                os.path.isabs(x)
-                    and os.path.commonpath([x, self.env.get_source_dir()]) == self.env.get_source_dir()
+                    path_is_in_root(x, Path(self.env.get_source_dir()))
                     and not (
-                        os.path.commonpath([x, root_src_dir]) == root_src_dir or
-                        os.path.commonpath([x, self.env.get_build_dir()]) == self.env.get_build_dir()
+                        path_is_in_root(x, root_src_dir) or
+                        path_is_in_root(x, Path(self.env.get_build_dir()))
                     )
                 ):
-                mlog.warning('CMake: path', mlog.bold(x), 'is inside the root project but', mlog.bold('not'), 'inside the subproject.')
+                mlog.warning('CMake: path', mlog.bold(x.as_posix()), 'is inside the root project but', mlog.bold('not'), 'inside the subproject.')
                 mlog.warning(' --> Ignoring. This can lead to build errors.')
                 return None
-            if os.path.isabs(x) and os.path.commonpath([x, self.env.get_build_dir()]) == self.env.get_build_dir():
-                if is_header:
-                    return os.path.relpath(x, os.path.join(self.env.get_build_dir(), subdir))
-                else:
-                    return os.path.relpath(x, root_src_dir)
-            if os.path.isabs(x) and os.path.commonpath([x, root_src_dir]) == root_src_dir:
-                return os.path.relpath(x, root_src_dir)
+            if path_is_in_root(x, Path(self.env.get_build_dir())) and is_header:
+                return x.relative_to(Path(self.env.get_build_dir()) / subdir)
+            if path_is_in_root(x, root_src_dir):
+                return x.relative_to(root_src_dir)
             return x
 
-        build_dir_rel = os.path.relpath(self.build_dir, os.path.join(self.env.get_build_dir(), subdir))
+        build_dir_rel = self.build_dir.relative_to(Path(self.env.get_build_dir()) / subdir)
         self.generated_raw = [rel_path(x, False, True) for x in self.generated_raw]
         self.includes = list(OrderedSet([rel_path(x, True, False) for x in OrderedSet(self.includes)] + [build_dir_rel]))
         self.sys_includes = list(OrderedSet([rel_path(x, True, False) for x in OrderedSet(self.sys_includes)]))
@@ -496,13 +495,13 @@ class ConverterTarget:
         self.sources      = [x for x in self.sources      if x is not None]
 
         # Make sure '.' is always in the include directories
-        if '.' not in self.includes:
-            self.includes += ['.']
+        if Path('.') not in self.includes:
+            self.includes += [Path('.')]
 
         # make install dir relative to the install prefix
-        if self.install_dir and os.path.isabs(self.install_dir):
-            if os.path.commonpath([self.install_dir, install_prefix]) == install_prefix:
-                self.install_dir = os.path.relpath(self.install_dir, install_prefix)
+        if self.install_dir and self.install_dir.is_absolute():
+            if path_is_in_root(self.install_dir, install_prefix):
+                self.install_dir = self.install_dir.relative_to(install_prefix)
 
         # Remove blacklisted options and libs
         def check_flag(flag: str) -> bool:
@@ -523,16 +522,13 @@ class ConverterTarget:
 
     def process_object_libs(self, obj_target_list: T.List['ConverterTarget'], linker_workaround: bool) -> None:
         # Try to detect the object library(s) from the generated input sources
-        temp = [x for x in self.generated]
-        temp = [os.path.basename(x) for x in temp]
-        temp = [x for x in temp if any([x.endswith('.' + y) for y in obj_suffixes])]
-        temp = [os.path.splitext(x)[0] for x in temp]
+        temp = [x for x in self.generated if any([x.name.endswith('.' + y) for y in obj_suffixes])]
+        stem = [x.stem for x in temp]
         exts = self._all_source_suffixes()
         # Temp now stores the source filenames of the object files
         for i in obj_target_list:
-            source_files = [x for x in i.sources + i.generated]
-            source_files = [os.path.basename(x) for x in source_files]
-            for j in temp:
+            source_files = [x.name for x in i.sources + i.generated]
+            for j in stem:
                 # On some platforms (specifically looking at you Windows with vs20xy backend) CMake does
                 # not produce object files with the format `foo.cpp.obj`, instead it skipps the language
                 # suffix and just produces object files like `foo.obj`. Thus we have to do our best to
@@ -552,7 +548,7 @@ class ConverterTarget:
                     break
 
         # Filter out object files from the sources
-        self.generated = [x for x in self.generated if not any([x.endswith('.' + y) for y in obj_suffixes])]
+        self.generated = [x for x in self.generated if not any([x.name.endswith('.' + y) for y in obj_suffixes])]
 
     def _append_objlib_sources(self, tgt: 'ConverterTarget') -> None:
         self.includes       += tgt.includes
@@ -618,7 +614,7 @@ class ConverterTarget:
         mlog.log('  -- full_name:      ', mlog.bold(self.full_name))
         mlog.log('  -- type:           ', mlog.bold(self.type))
         mlog.log('  -- install:        ', mlog.bold('true' if self.install else 'false'))
-        mlog.log('  -- install_dir:    ', mlog.bold(self.install_dir))
+        mlog.log('  -- install_dir:    ', mlog.bold(self.install_dir.as_posix() if self.install_dir else ''))
         mlog.log('  -- link_libraries: ', mlog.bold(str(self.link_libraries)))
         mlog.log('  -- link_with:      ', mlog.bold(str(self.link_with)))
         mlog.log('  -- object_libs:    ', mlog.bold(str(self.object_libs)))
@@ -666,15 +662,15 @@ class ConverterCustomTarget:
             ConverterCustomTarget.tgt_counter += 1
         self.cmake_name       = str(self.name)
         self.original_outputs = list(target.outputs)
-        self.outputs          = [os.path.basename(x) for x in self.original_outputs]
-        self.conflict_map     = {}                   # type: T.Dict[str, str]
-        self.command          = []                   # type: T.List[T.List[T.Union[str, ConverterTarget]]]
+        self.outputs          = [x.name for x in self.original_outputs]
+        self.conflict_map     = {}                      # type: T.Dict[str, str]
+        self.command          = []                      # type: T.List[T.List[T.Union[str, ConverterTarget]]]
         self.working_dir      = target.working_dir
         self.depends_raw      = target.depends
-        self.inputs           = []                   # type: T.List[T.Union[str, CustomTargetReference]]
-        self.depends          = []                   # type: T.List[T.Union[ConverterTarget, ConverterCustomTarget]]
-        self.current_bin_dir  = Path(target.current_bin_dir)
-        self.current_src_dir  = Path(target.current_src_dir)
+        self.inputs           = []                      # type: T.List[T.Union[str, CustomTargetReference]]
+        self.depends          = []                      # type: T.List[T.Union[ConverterTarget, ConverterCustomTarget]]
+        self.current_bin_dir  = target.current_bin_dir  # type: Path
+        self.current_src_dir  = target.current_src_dir  # type: Path
         self._raw_target      = target
 
         # Convert the target name to a valid meson target name
@@ -683,15 +679,15 @@ class ConverterCustomTarget:
     def __repr__(self) -> str:
         return '<{}: {} {}>'.format(self.__class__.__name__, self.name, self.outputs)
 
-    def postprocess(self, output_target_map: OutputTargetMap, root_src_dir: str, subdir: str, all_outputs: T.List[str], trace: CMakeTraceParser) -> None:
+    def postprocess(self, output_target_map: OutputTargetMap, root_src_dir: Path, all_outputs: T.List[str], trace: CMakeTraceParser) -> None:
         # Default the working directory to ${CMAKE_CURRENT_BINARY_DIR}
-        if not self.working_dir:
-            self.working_dir = self.current_bin_dir.as_posix()
+        if self.working_dir is None:
+            self.working_dir = self.current_bin_dir
 
         # relative paths in the working directory are always relative
         # to ${CMAKE_CURRENT_BINARY_DIR}
-        if not os.path.isabs(self.working_dir):
-            self.working_dir = (self.current_bin_dir / self.working_dir).as_posix()
+        if not self.working_dir.is_absolute():
+            self.working_dir = self.current_bin_dir / self.working_dir
 
         # Modify the original outputs if they are relative. Again,
         # relative paths are relative to ${CMAKE_CURRENT_BINARY_DIR}
@@ -700,7 +696,7 @@ class ConverterCustomTarget:
                 return x
             else:
                 return self.current_bin_dir / x
-        self.original_outputs = [ensure_absolute(Path(x)).as_posix() for x in self.original_outputs]
+        self.original_outputs = [ensure_absolute(x) for x in self.original_outputs]
 
         # Ensure that there is no duplicate output in the project so
         # that meson can handle cases where the same filename is
@@ -748,18 +744,17 @@ class ConverterCustomTarget:
             self.outputs = [self.name + '.h']
 
         # Check dependencies and input files
-        root = Path(root_src_dir)
         for i in self.depends_raw:
             if not i:
                 continue
             raw = Path(i)
             art = output_target_map.artifact(i)
             tgt = output_target_map.target(i)
-            gen = output_target_map.generated(i)
+            gen = output_target_map.generated(raw)
 
             rel_to_root = None
             try:
-                rel_to_root = raw.relative_to(root)
+                rel_to_root = raw.relative_to(root_src_dir)
             except ValueError:
                 rel_to_root = None
 
@@ -768,7 +763,7 @@ class ConverterCustomTarget:
             # as outputs from other targets.
             # See https://github.com/mesonbuild/meson/issues/6632
             if not raw.is_absolute() and (self.current_src_dir / raw).exists():
-                self.inputs += [(self.current_src_dir / raw).relative_to(root).as_posix()]
+                self.inputs += [(self.current_src_dir / raw).relative_to(root_src_dir).as_posix()]
             elif raw.is_absolute() and raw.exists() and rel_to_root is not None:
                 self.inputs += [rel_to_root.as_posix()]
             elif art:
@@ -776,7 +771,7 @@ class ConverterCustomTarget:
             elif tgt:
                 self.depends += [tgt]
             elif gen:
-                ctgt_ref = gen.get_ref(i)
+                ctgt_ref = gen.get_ref(raw)
                 assert ctgt_ref is not None
                 self.inputs += [ctgt_ref]
 
@@ -793,12 +788,12 @@ class ConverterCustomTarget:
                 new_deps += [i]
         self.depends = list(OrderedSet(new_deps))
 
-    def get_ref(self, fname: str) -> T.Optional[CustomTargetReference]:
-        fname = os.path.basename(fname)
+    def get_ref(self, fname: Path) -> T.Optional[CustomTargetReference]:
+        name = fname.name
         try:
-            if fname in self.conflict_map:
-                fname = self.conflict_map[fname]
-            idx = self.outputs.index(fname)
+            if name in self.conflict_map:
+                name = self.conflict_map[name]
+            idx = self.outputs.index(name)
             return CustomTargetReference(self, idx)
         except ValueError:
             return None
@@ -818,23 +813,22 @@ class CMakeAPI(Enum):
     FILE = 2
 
 class CMakeInterpreter:
-    def __init__(self, build: 'Build', subdir: str, src_dir: str, install_prefix: str, env: 'Environment', backend: 'Backend'):
-        assert(hasattr(backend, 'name'))
-        self.build = build
-        self.subdir = subdir
-        self.src_dir = src_dir
-        self.build_dir_rel = os.path.join(subdir, '__CMake_build')
-        self.build_dir = os.path.join(env.get_build_dir(), self.build_dir_rel)
+    def __init__(self, build: 'Build', subdir: Path, src_dir: Path, install_prefix: Path, env: 'Environment', backend: 'Backend'):
+        self.build          = build
+        self.subdir         = subdir
+        self.src_dir        = src_dir
+        self.build_dir_rel  = subdir / '__CMake_build'
+        self.build_dir      = Path(env.get_build_dir()) / self.build_dir_rel
         self.install_prefix = install_prefix
-        self.env = env
-        self.backend_name = backend.name
-        self.linkers = set()  # type: T.Set[str]
-        self.cmake_api = CMakeAPI.SERVER
-        self.client = CMakeClient(self.env)
-        self.fileapi = CMakeFileAPI(self.build_dir)
+        self.env            = env
+        self.backend_name   = backend.name
+        self.linkers        = set()  # type: T.Set[str]
+        self.cmake_api      = CMakeAPI.SERVER
+        self.client         = CMakeClient(self.env)
+        self.fileapi        = CMakeFileAPI(self.build_dir)
 
         # Raw CMake results
-        self.bs_files          = []    # type: T.List[str]
+        self.bs_files          = []    # type: T.List[Path]
         self.codemodel_configs = None  # type: T.Optional[T.List[CMakeConfiguration]]
         self.raw_trace         = None  # type: T.Optional[str]
 
@@ -843,7 +837,7 @@ class CMakeInterpreter:
         self.languages         = []  # type: T.List[str]
         self.targets           = []  # type: T.List[ConverterTarget]
         self.custom_targets    = []  # type: T.List[ConverterCustomTarget]
-        self.trace             = CMakeTraceParser('', '')  # Will be replaced in analyse
+        self.trace             = CMakeTraceParser('', Path('.'))  # Will be replaced in analyse
         self.output_target_map = OutputTargetMap(self.build_dir)
 
         # Generated meson data
@@ -899,16 +893,16 @@ class CMakeInterpreter:
         with mlog.nested():
             mlog.log('Configuring the build directory with', mlog.bold('CMake'), 'version', mlog.cyan(cmake_exe.version()))
             mlog.log(mlog.bold('Running:'), ' '.join(cmake_args))
-            mlog.log(mlog.bold('  - build directory:         '), self.build_dir)
-            mlog.log(mlog.bold('  - source directory:        '), self.src_dir)
+            mlog.log(mlog.bold('  - build directory:         '), self.build_dir.as_posix())
+            mlog.log(mlog.bold('  - source directory:        '), self.src_dir.as_posix())
             mlog.log(mlog.bold('  - trace args:              '), ' '.join(trace_args))
-            mlog.log(mlog.bold('  - preload file:            '), str(preload_file))
+            mlog.log(mlog.bold('  - preload file:            '), preload_file.as_posix())
             mlog.log(mlog.bold('  - disabled policy warnings:'), '[{}]'.format(', '.join(disable_policy_warnings)))
             mlog.log()
-            os.makedirs(self.build_dir, exist_ok=True)
-            os_env = os.environ.copy()
+            self.build_dir.mkdir(parents=True, exist_ok=True)
+            os_env = environ.copy()
             os_env['LC_ALL'] = 'C'
-            final_args = cmake_args + trace_args + cmcmp_args + pload_args + [self.src_dir]
+            final_args = cmake_args + trace_args + cmcmp_args + pload_args + [self.src_dir.as_posix()]
 
             cmake_exe.set_exec_mode(print_cmout=True, always_capture_stderr=self.trace.requires_stderr())
             rc, _, self.raw_trace = cmake_exe.call(final_args, self.build_dir, env=os_env, disable_cache=True)
@@ -933,7 +927,7 @@ class CMakeInterpreter:
             # Load the buildsystem file list
             cmake_files = self.fileapi.get_cmake_sources()
             self.bs_files = [x.file for x in cmake_files if not x.is_cmake and not x.is_temp]
-            self.bs_files = [os.path.relpath(x, self.env.get_source_dir()) for x in self.bs_files]
+            self.bs_files = [relative_to_if_possible(x, Path(self.env.get_source_dir())) for x in self.bs_files]
             self.bs_files = list(OrderedSet(self.bs_files))
 
             # Load the codemodel configurations
@@ -960,7 +954,7 @@ class CMakeInterpreter:
 
         src_dir = bs_reply.src_dir
         self.bs_files = [x.file for x in bs_reply.build_files if not x.is_cmake and not x.is_temp]
-        self.bs_files = [os.path.relpath(os.path.join(src_dir, x), self.env.get_source_dir()) for x in self.bs_files]
+        self.bs_files = [relative_to_if_possible(src_dir / x, Path(self.env.get_source_dir()), resolve=True) for x in self.bs_files]
         self.bs_files = list(OrderedSet(self.bs_files))
         self.codemodel_configs = cm_reply.configs
 
@@ -1017,7 +1011,7 @@ class CMakeInterpreter:
         object_libs = []
         custom_target_outputs = []  # type: T.List[str]
         for ctgt in self.custom_targets:
-            ctgt.postprocess(self.output_target_map, self.src_dir, self.subdir, custom_target_outputs, self.trace)
+            ctgt.postprocess(self.output_target_map, self.src_dir, custom_target_outputs, self.trace)
         for tgt in self.targets:
             tgt.postprocess(self.output_target_map, self.src_dir, self.subdir, self.install_prefix, self.trace)
             if tgt.type == 'OBJECT_LIBRARY':
@@ -1045,7 +1039,7 @@ class CMakeInterpreter:
             raise CMakeException('CMakeInterpreter was not analysed')
 
         def token(tid: str = 'string', val: TYPE_mixed = '') -> Token:
-            return Token(tid, self.subdir, 0, 0, 0, None, val)
+            return Token(tid, self.subdir.as_posix(), 0, 0, 0, None, val)
 
         def string(value: str) -> StringNode:
             return StringNode(token(val=value))
@@ -1059,6 +1053,8 @@ class CMakeInterpreter:
         def nodeify(value: TYPE_mixed_list) -> BaseNode:
             if isinstance(value, str):
                 return string(value)
+            if isinstance(value, Path):
+                return string(value.as_posix())
             elif isinstance(value, bool):
                 return BooleanNode(token(val=value))
             elif isinstance(value, int):
@@ -1084,11 +1080,11 @@ class CMakeInterpreter:
             kwargs = {} if kwargs is None else kwargs
             args_n = ArgumentNode(token())
             if not isinstance(args, list):
-                assert isinstance(args, (str, int, bool, BaseNode))
+                assert isinstance(args, (str, int, bool, Path, BaseNode))
                 args = [args]
             args_n.arguments = [nodeify(x) for x in args if x is not None]
             args_n.kwargs = {id_node(k): nodeify(v) for k, v in kwargs.items() if v is not None}
-            func_n = FunctionNode(self.subdir, 0, 0, 0, 0, name, args_n)
+            func_n = FunctionNode(self.subdir.as_posix(), 0, 0, 0, 0, name, args_n)
             return func_n
 
         def method(obj: BaseNode, name: str, args: T.Optional[TYPE_mixed_list] = None, kwargs: T.Optional[TYPE_mixed_kwargs] = None) -> MethodNode:
@@ -1096,14 +1092,14 @@ class CMakeInterpreter:
             kwargs = {} if kwargs is None else kwargs
             args_n = ArgumentNode(token())
             if not isinstance(args, list):
-                assert isinstance(args, (str, int, bool, BaseNode))
+                assert isinstance(args, (str, int, bool, Path, BaseNode))
                 args = [args]
             args_n.arguments = [nodeify(x) for x in args if x is not None]
             args_n.kwargs = {id_node(k): nodeify(v) for k, v in kwargs.items() if v is not None}
-            return MethodNode(self.subdir, 0, 0, obj, name, args_n)
+            return MethodNode(self.subdir.as_posix(), 0, 0, obj, name, args_n)
 
         def assign(var_name: str, value: BaseNode) -> AssignmentNode:
-            return AssignmentNode(self.subdir, 0, 0, var_name, value)
+            return AssignmentNode(self.subdir.as_posix(), 0, 0, var_name, value)
 
         # Generate the root code block and the project function call
         root_cb = CodeBlockNode(token())
@@ -1144,7 +1140,7 @@ class CMakeInterpreter:
             # First handle inter target dependencies
             link_with           = []  # type: T.List[IdNode]
             objec_libs          = []  # type: T.List[IdNode]
-            sources             = []  # type: T.List[str]
+            sources             = []  # type: T.List[Path]
             generated           = []  # type: T.List[T.Union[IdNode, IndexNode]]
             generated_filenames = []  # type: T.List[str]
             custom_targets      = []  # type: T.List[ConverterCustomTarget]
@@ -1190,7 +1186,7 @@ class CMakeInterpreter:
                     if not is_header(j) or j in generated_filenames:
                         continue
 
-                    generated += [resolve_ctgt_ref(ctgt.get_ref(j))]
+                    generated += [resolve_ctgt_ref(ctgt.get_ref(Path(j)))]
                     generated_filenames += [j]
 
             # Determine the meson function to use for the build target
@@ -1305,8 +1301,8 @@ class CMakeInterpreter:
             command += ['--internal', 'cmake_run_ctgt']
             command += ['-o', '@OUTPUT@']
             if tgt.original_outputs:
-                command += ['-O'] + tgt.original_outputs
-            command += ['-d', tgt.working_dir]
+                command += ['-O'] + [x.as_posix() for x in tgt.original_outputs]
+            command += ['-d', tgt.working_dir.as_posix()]
 
             # Generate the commands. Subcommands are separated by ';;;'
             for cmd in tgt.command:
diff --git a/mesonbuild/cmake/traceparser.py b/mesonbuild/cmake/traceparser.py
index 5c41196..bee011c 100644
--- a/mesonbuild/cmake/traceparser.py
+++ b/mesonbuild/cmake/traceparser.py
@@ -23,12 +23,11 @@ from ..mesonlib import version_compare
 import typing as T
 from pathlib import Path
 import re
-import os
 import json
 import textwrap
 
 class CMakeTraceLine:
-    def __init__(self, file: str, line: int, func: str, args: T.List[str]) -> None:
+    def __init__(self, file: Path, line: int, func: str, args: T.List[str]) -> None:
         self.file = file
         self.line = line
         self.func = func.lower()
@@ -55,8 +54,8 @@ class CMakeTarget:
         self.imported        = imported
         self.tline           = tline
         self.depends         = []      # type: T.List[str]
-        self.current_bin_dir = None    # type: T.Optional[str]
-        self.current_src_dir = None    # type: T.Optional[str]
+        self.current_bin_dir = None    # type: T.Optional[Path]
+        self.current_src_dir = None    # type: T.Optional[Path]
 
     def __repr__(self) -> str:
         s = 'CMake TARGET:\n  -- name:      {}\n  -- type:      {}\n  -- imported:  {}\n  -- properties: {{\n{}     }}\n  -- tline: {}'
@@ -76,12 +75,12 @@ class CMakeTarget:
 class CMakeGeneratorTarget(CMakeTarget):
     def __init__(self, name: str) -> None:
         super().__init__(name, 'CUSTOM', {})
-        self.outputs = []        # type: T.List[str]
+        self.outputs = []        # type: T.List[Path]
         self.command = []        # type: T.List[T.List[str]]
-        self.working_dir = None  # type: T.Optional[str]
+        self.working_dir = None  # type: T.Optional[Path]
 
 class CMakeTraceParser:
-    def __init__(self, cmake_version: str, build_dir: str, permissive: bool = True) -> None:
+    def __init__(self, cmake_version: str, build_dir: Path, permissive: bool = True) -> None:
         self.vars = {}     # type: T.Dict[str, T.List[str]]
         self.targets = {}  # type: T.Dict[str, CMakeTarget]
 
@@ -93,7 +92,7 @@ class CMakeTraceParser:
         self.permissive = permissive  # type: bool
         self.cmake_version = cmake_version  # type: str
         self.trace_file = 'cmake_trace.txt'
-        self.trace_file_path = Path(build_dir) / self.trace_file
+        self.trace_file_path = build_dir / self.trace_file
         self.trace_format = 'json-v1' if version_compare(cmake_version, '>=3.17') else 'human'
 
         # State for delayed command execution. Delayed command execution is realised
@@ -339,7 +338,7 @@ class CMakeTraceParser:
         target = CMakeGeneratorTarget(name)
 
         def handle_output(key: str, target: CMakeGeneratorTarget) -> None:
-            target.outputs += [key]
+            target.outputs += [Path(key)]
 
         def handle_command(key: str, target: CMakeGeneratorTarget) -> None:
             if key == 'ARGS':
@@ -349,12 +348,14 @@ class CMakeTraceParser:
         def handle_depends(key: str, target: CMakeGeneratorTarget) -> None:
             target.depends += [key]
 
+        working_dir = None
         def handle_working_dir(key: str, target: CMakeGeneratorTarget) -> None:
-            if target.working_dir is None:
-                target.working_dir = key
+            nonlocal working_dir
+            if working_dir is None:
+                working_dir = key
             else:
-                target.working_dir += ' '
-                target.working_dir += key
+                working_dir += ' '
+                working_dir += key
 
         fn = None
 
@@ -376,9 +377,13 @@ class CMakeTraceParser:
             if fn is not None:
                 fn(i, target)
 
-        target.current_bin_dir = self.var_to_str('MESON_PS_CMAKE_CURRENT_BINARY_DIR')
-        target.current_src_dir = self.var_to_str('MESON_PS_CMAKE_CURRENT_SOURCE_DIR')
-        target.outputs = self._guess_files(target.outputs)
+        cbinary_dir = self.var_to_str('MESON_PS_CMAKE_CURRENT_BINARY_DIR')
+        csource_dir = self.var_to_str('MESON_PS_CMAKE_CURRENT_SOURCE_DIR')
+
+        target.working_dir     = Path(working_dir) if working_dir else None
+        target.current_bin_dir = Path(cbinary_dir) if cbinary_dir else None
+        target.current_src_dir = Path(csource_dir) if csource_dir else None
+        target.outputs = [Path(x) for x in self._guess_files([str(y) for y in target.outputs])]
         target.depends = self._guess_files(target.depends)
         target.command = [self._guess_files(x) for x in target.command]
 
@@ -639,7 +644,7 @@ class CMakeTraceParser:
             argl = args.split(' ')
             argl = list(map(lambda x: x.strip(), argl))
 
-            yield CMakeTraceLine(file, int(line), func, argl)
+            yield CMakeTraceLine(Path(file), int(line), func, argl)
 
     def _lex_trace_json(self, trace: str) -> T.Generator[CMakeTraceLine, None, None]:
         lines = trace.splitlines(keepends=False)
@@ -654,7 +659,7 @@ class CMakeTraceParser:
             for j in args:
                 assert isinstance(j, str)
             args = [parse_generator_expressions(x) for x in args]
-            yield CMakeTraceLine(data['file'], data['line'], data['cmd'], args)
+            yield CMakeTraceLine(Path(data['file']), data['line'], data['cmd'], args)
 
     def _flatten_args(self, args: T.List[str]) -> T.List[str]:
         # Split lists in arguments
@@ -681,7 +686,7 @@ class CMakeTraceParser:
             if curr_str is None:
                 curr_str = i
                 path_found = False
-            elif os.path.isfile(curr_str):
+            elif Path(curr_str).is_file():
                 # Abort concatenation if curr_str is an existing file
                 fixed_list += [curr_str]
                 curr_str = i
@@ -697,7 +702,7 @@ class CMakeTraceParser:
                 fixed_list += [curr_str]
                 curr_str = None
                 path_found = False
-            elif os.path.exists('{} {}'.format(curr_str, i)):
+            elif Path('{} {}'.format(curr_str, i)).exists():
                 # Path detected
                 curr_str = '{} {}'.format(curr_str, i)
                 path_found = True
diff --git a/mesonbuild/dependencies/base.py b/mesonbuild/dependencies/base.py
index 7b2f2d9..e622859 100644
--- a/mesonbuild/dependencies/base.py
+++ b/mesonbuild/dependencies/base.py
@@ -1528,12 +1528,12 @@ class CMakeDependency(ExternalDependency):
         self.compile_args = compileOptions + compileDefinitions + ['-I{}'.format(x) for x in incDirs]
         self.link_args = libraries
 
-    def _get_build_dir(self) -> str:
+    def _get_build_dir(self) -> Path:
         build_dir = Path(self.cmake_root_dir) / 'cmake_{}'.format(self.name)
         build_dir.mkdir(parents=True, exist_ok=True)
-        return str(build_dir)
+        return build_dir
 
-    def _setup_cmake_dir(self, cmake_file: str) -> str:
+    def _setup_cmake_dir(self, cmake_file: str) -> Path:
         # Setup the CMake build environment and return the "build" directory
         build_dir = self._get_build_dir()
 
@@ -1557,7 +1557,7 @@ cmake_minimum_required(VERSION ${{CMAKE_VERSION}})
 project(MesonTemp LANGUAGES {})
 """.format(' '.join(cmake_language)) + cmake_txt
 
-        cm_file = Path(build_dir) / 'CMakeLists.txt'
+        cm_file = build_dir / 'CMakeLists.txt'
         cm_file.write_text(cmake_txt)
         mlog.cmd_ci_include(cm_file.absolute().as_posix())
 
diff --git a/mesonbuild/interpreter.py b/mesonbuild/interpreter.py
index c56eff5..eb67a45 100644
--- a/mesonbuild/interpreter.py
+++ b/mesonbuild/interpreter.py
@@ -2983,7 +2983,7 @@ external dependencies (including libraries) must go to "dependencies".''')
 
             cmake_options = mesonlib.stringlistify(kwargs.get('cmake_options', []))
             cmake_options += options.cmake_options
-            cm_int = CMakeInterpreter(new_build, subdir, subdir_abs, prefix, new_build.environment, self.backend)
+            cm_int = CMakeInterpreter(new_build, Path(subdir), Path(subdir_abs), Path(prefix), new_build.environment, self.backend)
             cm_int.initialise(cmake_options)
             cm_int.analyse()
 
diff --git a/mesonbuild/mesonlib.py b/mesonbuild/mesonlib.py
index f297771..0b614ba 100644
--- a/mesonbuild/mesonlib.py
+++ b/mesonbuild/mesonlib.py
@@ -1570,6 +1570,15 @@ def path_is_in_root(path: Path, root: Path, resolve: bool = False) -> bool:
         return False
     return True
 
+def relative_to_if_possible(path: Path, root: Path, resolve: bool = False) -> Path:
+    try:
+        if resolve:
+            return path.resolve().relative_to(root.resolve())
+        else:
+            return path.relative_to(root)
+    except ValueError:
+        return path
+
 class LibType(IntEnum):
 
     """Enumeration for library types."""