fill out ???s and link to issues for TODOs

pants.ini

@@ -403,6 +403,6 @@ fragment: True
 [sitegen]
 config_path: src/docs/docsite.json
 
-# TODO(#???): this should be removed when we can fully support both toolchains.
+# TODO(#6848): this should be removed when we can fully support both toolchains.
 [native-build-settings]
 toolchain_variant: llvm

src/python/pants/backend/native/config/environment.py

@@ -96,7 +96,10 @@ def linking_library_dirs(self):
 
   @abstractproperty
   def extra_object_files(self):
-    """???"""
+    """A list of object files required to perform a successful link.
+
+    This includes crti.o from libc for gcc on Linux, for example.
+    """
 
   @property
   def as_invocation_environment_dict(self):

tests/python/pants_test/backend/python/tasks/test_ctypes_integration.py

@@ -188,7 +188,7 @@ def _assert_ctypes_interop_with_mock_buildroot(self, toolchain_variant):
         command=['binary', self._binary_target_with_interop],
         # Explicitly set to True (although this is the default).
         config={
-          # TODO: don't make it possible to forget to add the toolchain_variant option!
+          # TODO(#6848): don't make it possible to forget to add the toolchain_variant option!
           'native-build-settings': {
             'toolchain_variant': toolchain_variant,
             'strict_deps': True,
@@ -200,7 +200,7 @@ def _assert_ctypes_interop_with_mock_buildroot(self, toolchain_variant):
       self.assertIn(self._include_not_found_message_for_variant[toolchain_variant],
                     pants_binary_strict_deps_failure.stdout_data)
 
-    # TODO(#???): we need to provide the libstdc++.so.6.dylib which comes with gcc on osx in the
+    # TODO(#6848): we need to provide the libstdc++.so.6.dylib which comes with gcc on osx in the
     # DYLD_LIBRARY_PATH during the 'run' goal somehow.
     attempt_pants_run = Platform.create().resolve_platform_specific({
       'darwin': lambda: toolchain_variant != 'gnu',
@@ -224,7 +224,7 @@ def test_ctypes_third_party_integration(self):
     pants_binary = self.run_pants(['binary', self._binary_target_with_third_party])
     self.assert_success(pants_binary)
 
-    # TODO(#???): this fails when run with gcc on osx as it requires gcc's libstdc++.so.6.dylib to
+    # TODO(#6848): this fails when run with gcc on osx as it requires gcc's libstdc++.so.6.dylib to
     # be available on the runtime library path.
     pants_run = self.run_pants(['-q', 'run', self._binary_target_with_third_party])
     self.assert_success(pants_run)

tests/python/pants_test/backend/python/tasks/util/build_local_dists_test_base.py

@@ -115,7 +115,7 @@ def _create_distribution_synthetic_target(self, python_dist_target, extra_target
       target_roots=([python_dist_target] + extra_targets),
       for_task_types=(all_synthesized_task_types),
       for_subsystems=[PythonRepos, LibcDev],
-      # TODO(#???): we should be testing all of these with both of our toolchains.
+      # TODO(#6848): we should be testing all of these with both of our toolchains.
       options={
         'native-build-settings': {
           'toolchain_variant': 'llvm',