Fix linking against libraries from Meson project on macOS

Author: pastewka

meson.build

@@ -10,6 +10,7 @@ endif
 py.install_sources(
   'mesonpy/__init__.py',
   'mesonpy/_compat.py',
+  'mesonpy/_dylib.py',
   'mesonpy/_editable.py',
   'mesonpy/_elf.py',
   'mesonpy/_introspection.py',

mesonpy/__init__.py

@@ -44,6 +44,7 @@
 
 
 import mesonpy._compat
+import mesonpy._dylib
 import mesonpy._elf
 import mesonpy._introspection
 import mesonpy._tags
@@ -509,19 +510,28 @@ def _install_path(
                         arcname = os.path.join(destination, os.path.relpath(path, origin).replace(os.path.sep, '/'))
                         wheel_file.write(path, arcname)
         else:
-            if self._has_internal_libs and platform.system() == 'Linux':
-                # add .mesonpy.libs to the RPATH of ELF files
-                if self._is_native(os.fspath(origin)):
-                    # copy ELF to our working directory to avoid Meson having to regenerate the file
-                    new_origin = self._libs_build_dir / pathlib.Path(origin).relative_to(self._build_dir)
-                    os.makedirs(new_origin.parent, exist_ok=True)
-                    shutil.copy2(origin, new_origin)
-                    origin = new_origin
-                    # add our in-wheel libs folder to the RPATH
-                    elf = mesonpy._elf.ELF(origin)
-                    libdir_path = f'$ORIGIN/{os.path.relpath(f".{self._project.name}.mesonpy.libs", destination.parent)}'
-                    if libdir_path not in elf.rpath:
-                        elf.rpath = [*elf.rpath, libdir_path]
+            if self._has_internal_libs:
+                if platform.system() == 'Linux' or platform.system() == 'Darwin':
+                    # add .mesonpy.libs to the RPATH of ELF files
+                    if self._is_native(os.fspath(origin)):
+                        # copy ELF to our working directory to avoid Meson having to regenerate the file
+                        new_origin = self._libs_build_dir / pathlib.Path(origin).relative_to(self._build_dir)
+                        os.makedirs(new_origin.parent, exist_ok=True)
+                        shutil.copy2(origin, new_origin)
+                        origin = new_origin
+                        # add our in-wheel libs folder to the RPATH
+                        if platform.system() == 'Linux':
+                            elf = mesonpy._elf.ELF(origin)
+                            libdir_path = \
+                                f'$ORIGIN/{os.path.relpath(f".{self._project.name}.mesonpy.libs", destination.parent)}'
+                            if libdir_path not in elf.rpath:
+                                elf.rpath = [*elf.rpath, libdir_path]
+                        else:  # 'Darwin'
+                            dylib = mesonpy._dylib.Dylib(origin)
+                            libdir_path = \
+                                f'@loader_path/{os.path.relpath(f".{self._project.name}.mesonpy.libs", destination.parent)}'
+                            if libdir_path not in dylib.rpath:
+                                dylib.rpath = [*dylib.rpath, libdir_path]
 
             wheel_file.write(origin, location)
 
@@ -558,7 +568,8 @@ def build(self, directory: Path) -> pathlib.Path:
 
                 # install bundled libraries
                 for destination, origin in self._wheel_files['mesonpy-libs']:
-                    assert platform.system() == 'Linux', 'Bundling libraries in wheel is currently only supported in POSIX!'
+                    assert platform.system() == 'Linux' or platform.system() == 'Darwin', \
+                        'Bundling libraries in wheel is currently only supported in POSIX!'
                     destination = pathlib.Path(f'.{self._project.name}.mesonpy.libs', destination)
                     self._install_path(whl, counter, origin, destination)
 

mesonpy/_dylib.py

@@ -0,0 +1,50 @@
+# SPDX-License-Identifier: MIT
+# SPDX-FileCopyrightText: 2023 Lars Pastewka <[email protected]>
+
+import os
+import subprocess
+
+from typing import Optional
+
+from mesonpy._compat import Collection, Path
+
+
+# This class is modeled after the ELF class in _elf.py
+class Dylib:
+    def __init__(self, path: Path) -> None:
+        self._path = os.fspath(path)
+        self._rpath: Optional[Collection[str]] = None
+        self._needed: Optional[Collection[str]] = None
+
+    def _otool(self, *args: str) -> str:
+        return subprocess.check_output(['otool', *args, self._path], stderr=subprocess.STDOUT).decode()
+
+    def _install_name_tool(self, *args: str) -> str:
+        return subprocess.check_output(['install_name_tool', *args, self._path], stderr=subprocess.STDOUT).decode()
+
+    @property
+    def rpath(self) -> Collection[str]:
+        if self._rpath is None:
+            self._rpath = []
+            # Run otool -l to get the load commands
+            otool_output = self._otool('-l').strip()
+            # Manually parse the output for LC_RPATH
+            rpath_tag = False
+            for line in [x.split() for x in otool_output.split('\n')]:
+                if line == ['cmd', 'LC_RPATH']:
+                    rpath_tag = True
+                elif len(line) >= 2 and line[0] == 'path' and rpath_tag:
+                    self._rpath += [line[1]]
+                    rpath_tag = False
+        return frozenset(self._rpath)
+
+    @rpath.setter
+    def rpath(self, value: Collection[str]) -> None:
+        # We clear all LC_RPATH load commands
+        if self._rpath:
+            for rpath in self._rpath:
+                self._install_name_tool('-delete_rpath', rpath)
+        # We then rewrite the new load commands
+        for rpath in value:
+            self._install_name_tool('-add_rpath', rpath)
+        self._rpath = value

tests/test_wheel.py

@@ -144,7 +144,7 @@ def test_configure_data(wheel_configure_data):
     }
 
 
-@pytest.mark.skipif(platform.system() != 'Linux', reason='Unsupported on this platform for now')
+@pytest.mark.skipif(platform.system() not in ['Linux', 'Darwin'], reason='Unsupported on this platform for now')
 def test_local_lib(venv, wheel_link_against_local_lib):
     venv.pip('install', wheel_link_against_local_lib)
     output = venv.python('-c', 'import example; print(example.example_sum(1, 2))')
@@ -184,25 +184,32 @@ def test_detect_wheel_tag_script(wheel_executable):
     assert name.group('plat') == PLATFORM
 
 
-@pytest.mark.skipif(platform.system() != 'Linux', reason='Unsupported on this platform for now')
+@pytest.mark.skipif(platform.system() not in ['Linux', 'Darwin'], reason='Unsupported on this platform for now')
 def test_rpath(wheel_link_against_local_lib, tmp_path):
     artifact = wheel.wheelfile.WheelFile(wheel_link_against_local_lib)
     artifact.extractall(tmp_path)
 
-    elf = mesonpy._elf.ELF(tmp_path / f'example{EXT_SUFFIX}')
-    assert '$ORIGIN/.link_against_local_lib.mesonpy.libs' in elf.rpath
+    if platform.system() == 'Linux':
+        elf = mesonpy._elf.ELF(tmp_path / f'example{EXT_SUFFIX}')
+        assert '$ORIGIN/.link_against_local_lib.mesonpy.libs' in elf.rpath
+    else:  # 'Darwin'
+        dylib = mesonpy._dylib.Dylib(tmp_path / f'example{EXT_SUFFIX}')
+        assert '@loader_path/.link_against_local_lib.mesonpy.libs' in dylib.rpath
 
 
-@pytest.mark.skipif(platform.system() != 'Linux', reason='Unsupported on this platform for now')
+@pytest.mark.skipif(platform.system() not in ['Linux', 'Darwin'], reason='Unsupported on this platform for now')
 def test_uneeded_rpath(wheel_purelib_and_platlib, tmp_path):
     artifact = wheel.wheelfile.WheelFile(wheel_purelib_and_platlib)
     artifact.extractall(tmp_path)
 
-    elf = mesonpy._elf.ELF(tmp_path / f'plat{EXT_SUFFIX}')
-    if elf.rpath:
-        # elf.rpath is a frozenset, so iterate over it. An rpath may be
+    if platform.system() == 'Linux':
+        shared_lib = mesonpy._elf.ELF(tmp_path / f'plat{EXT_SUFFIX}')
+    else:  # 'Darwin'
+        shared_lib = mesonpy._dylib.Dylib(tmp_path / f'plat{EXT_SUFFIX}')
+    if shared_lib.rpath:
+        # shared_lib.rpath is a frozenset, so iterate over it. An rpath may be
         # present, e.g. when conda is used (rpath will be <conda-prefix>/lib/)
-        for rpath in elf.rpath:
+        for rpath in shared_lib.rpath:
             assert 'mesonpy.libs' not in rpath