Fix hardcoded paths to libpython on macOS builds

Uses `install_name_tool` to adjust the search path of `libpython` to be relative to the executable.
Adds a test to validate that the path is relative on macOS.

Co-authored-by: Dean Moldovan <[email protected]>

Author: tiagobonetti

changelog.md

@@ -3,6 +3,7 @@
 ## v1.5.2 | 2023-04-18
 
 - Added a list of all installed packages to `licenses/packages.txt`.
+- Fixed executable's hardcoded search path for `libpython` on macOS.
 
 ## v1.5.1 | 2023-03-13
 

conanfile.py

@@ -1,6 +1,7 @@
 import os
 import pathlib
 import re
+from io import StringIO
 from conan import ConanFile
 from conan.tools.files import get, replace_in_file, download, rmdir, copy
 from conan.tools.scm import Version
@@ -337,6 +338,7 @@ def install(self):
 
         ver = ".".join(self.conanfile.pyversion.split(".")[:2])
         exe = str(self.prefix / f"bin/python{ver}")
+        self._patch_libpython_path(exe)
 
         specs = [
             f"pip=={self.conanfile.options.pip_version}",
@@ -362,3 +364,20 @@ def enable_site_packages(self):
     def build_bootstrap(self):
         """For now, as a shortcut, we'll let the Unix-like builds bootstrap themselves"""
         return self.prefix / "bin/python3"
+
+    def _patch_libpython_path(self, exe):
+        """Patch libpython search path"""
+        if self.conanfile.settings.os != "Macos":
+            return
+
+        buffer = StringIO()
+        self.conanfile.run(f"otool -L {exe}", output=buffer)
+        lines = buffer.getvalue().strip().split('\n')[1:]
+        libraries = [line.split()[0] for line in lines]
+
+        prefix = str(self.prefix)
+        hardcoded_libraries = [lib for lib in libraries if lib.startswith(prefix)]
+        for lib in hardcoded_libraries:
+            relocatable_library = lib.replace(prefix, "@executable_path/..")
+            self.conanfile.output.info(f"Patching {exe}, replace {lib} with {relocatable_library}")
+            self.conanfile.run(f"install_name_tool -change {lib} {relocatable_library} {exe}")

test_package/conanfile.py

@@ -1,5 +1,6 @@
 import pathlib
 import sys
+from io import StringIO
 from conan import ConanFile
 from conan.tools.cmake import CMake, CMakeToolchain
 
@@ -53,6 +54,23 @@ def _test_env(self):
         name = str(self.options.env) if self.options.env else "baseline"
         self.run(f"{python_exe} {project_root / name / 'test.py'}", run_environment=True)
 
+
+    def _test_libpython_path(self):
+        if self.settings.os != "Macos":
+            return
+
+        python_exe = str(pathlib.Path("./bin/python/bin/python3").resolve())
+        buffer = StringIO()
+        self.run(f'otool -L {python_exe}', run_environment=True, output=buffer)
+        lines = buffer.getvalue().strip().split('\n')[1:]
+        libraries = [line.split()[0] for line in lines]
+        candidates = [lib for lib in libraries if "libpython" in lib]
+        assert candidates, f"libpython dependency not found in 'otool' output: {libraries}"
+
+        for lib in candidates:
+            assert lib.startswith("@executable_path"), f"libpython has an unexpected prefix: {lib}"
+
+
     def _test_embed(self):
         """Ensure that everything is available to compile and link to the embedded Python"""
         self.run(pathlib.Path("bin", "test_package"), run_environment=True)
@@ -70,5 +88,6 @@ def _test_licenses(self):
 
     def test(self):
         self._test_env()
+        self._test_libpython_path()
         self._test_embed()
         self._test_licenses()