compilers/mixins: Add a module for mixins for compilers that are linkers

This is currently meant to solve problems for D's DMD compiler, however
it may be useful in other cases.

mesonbuild/compilers/mixins/islinker.py

@@ -0,0 +1,124 @@
+# Copyright 2019 The Meson development team
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Mixins for compilers that *are* linkers.
+
+While many compilers (such as gcc and clang) are used by meson to dispatch
+linker commands and other (like MSVC) are not, a few (such as DMD) actually
+are both the linker and compiler in one binary. This module provides mixin
+classes for those cases.
+"""
+
+import os
+import shlex
+import typing
+
+from ... import mesonlib
+
+if typing.TYPE_CHECKING:
+    from ...coredata import OptionDictType
+    from ...environment import Environment
+
+
+class LinkerEnvVarsMixin:
+
+    """Mixin reading LDFLAGS from the environment."""
+
+    def get_linker_args_from_envvars(self) -> typing.List[str]:
+        flags = os.environ.get('LDFLAGS')
+        if not flags:
+            return []
+        return shlex.split(flags)
+
+
+class BasicLinkerIsCompilerMixin:
+
+    """Provides a baseline of methods that a linker would implement.
+
+    In every case this provides a "no" or "empty" answer. If a compiler
+    implements any of these it needs a different mixin or to override that
+    functionality itself.
+    """
+
+    def sanitizer_link_args(self, value: str) -> typing.List[str]:
+        return []
+
+    def get_lto_link_args(self) -> typing.List[str]:
+        return []
+
+    def can_linker_accept_rsp(self) -> bool:
+        return mesonlib.is_windows()
+
+    def get_linker_exelist(self) -> typing.List[str]:
+        return self.exelist.copy()
+
+    def get_linker_output_args(self, output: str) -> typing.List[str]:
+        return []
+
+    def get_linker_always_args(self) -> typing.List[str]:
+        return []
+
+    def get_linker_lib_prefix(self) -> str:
+        return ''
+
+    def get_option_link_args(self, options: 'OptionDictType') -> typing.List[str]:
+        return []
+
+    def has_multi_link_args(self, args: typing.List[str], env: 'Environment') -> typing.Tuple[bool, bool]:
+        return False, False
+
+    def get_link_debugfile_args(self, targetfile: str) -> typing.List[str]:
+        return []
+
+    def get_std_shared_lib_link_args(self) -> typing.List[str]:
+        return []
+
+    def get_std_shared_module_args(self, options: 'OptionDictType') -> typing.List[str]:
+        return self.get_std_shared_lib_link_args()
+
+    def get_link_whole_for(self, args: typing.List[str]) -> typing.List[str]:
+        raise mesonlib.EnvironmentException(
+            'Linker {} does not support link_whole'.format(self.id))
+
+    def get_allow_undefined_args(self) -> typing.List[str]:
+        raise mesonlib.EnvironmentException(
+            'Linker {} does not support allow undefined'.format(self.id))
+
+    def get_pie_link_args(self) -> typing.List[str]:
+        m = 'Linker {} does not support position-independent executable'
+        raise mesonlib.EnvironmentException(m.format(self.id))
+
+    def get_undefined_link_args(self) -> typing.List[str]:
+        return []
+
+    def get_coverage_link_args(self) -> typing.List[str]:
+        m = "Linker {} doesn't implement coverage data generation.".format(self.id)
+        raise mesonlib.EnvironmentException(m)
+
+    def no_undefined_link_args(self) -> typing.List[str]:
+        return []
+
+    def bitcode_args(self) -> typing.List[str]:
+        raise mesonlib.MesonException("This linker doesn't support bitcode bundles")
+
+    def get_soname_args(self, for_machine: 'mesonlib.MachineChoice',
+                        prefix: str, shlib_name: str, suffix: str, soversion: str,
+                        darwin_versions: typing.Tuple[str, str],
+                        is_shared_module: bool) -> typing.List[str]:
+        raise mesonlib.MesonException("This linker doesn't support soname args")
+
+    def build_rpath_args(self, env: 'Environment', build_dir: str, from_dir: str,
+                         rpath_paths: str, build_rpath: str,
+                         install_rpath: str) -> typing.List[str]:
+        return []