swift: Add support for C++/Objective-C++ interoperability

As of Swift 5.9, C++/Objective-C++ code can be mixed with Swift, and
C++ APIs can be imported to Swift. However, this must be explicitly
enabled, as it is disabled by default.

Xcode 15 introduces a new setting for this, so only set it on Xcode 15
and above.

Author: tangalbert919

mesonbuild/backend/ninjabackend.py

@@ -2266,6 +2266,10 @@ def generate_swift_target(self, target) -> None:
         os.makedirs(self.get_target_private_dir_abs(target), exist_ok=True)
         compile_args = self.generate_basic_compiler_args(target, swiftc)
         compile_args += swiftc.get_module_args(module_name)
+        if mesonlib.version_compare(swiftc.version, '>=5.9'):
+            compile_args += swiftc.get_cxx_interoperability_args(target.compilers)
+        compile_args += self.build.get_project_args(swiftc, target.subproject, target.for_machine)
+        compile_args += self.build.get_global_args(swiftc, target.for_machine)
         for i in reversed(target.get_include_dirs()):
             basedir = i.get_curdir()
             for d in i.get_incdirs():

mesonbuild/backend/xcodebackend.py

@@ -1596,6 +1596,7 @@ def generate_single_build_target(self, objects_dict, target_name, target) -> Non
             headerdirs = []
             bridging_header = ""
             is_swift = self.is_swift_target(target)
+            langs = set()
             for d in target.include_dirs:
                 for sd in d.incdirs:
                     cd = os.path.join(d.curdir, sd)
@@ -1715,6 +1716,7 @@ def generate_single_build_target(self, objects_dict, target_name, target) -> Non
                         lang = 'c'
                     elif lang == 'objcpp':
                         lang = 'cpp'
+                    langs.add(lang)
                     langname = LANGNAMEMAP[lang]
                     langargs.setdefault(langname, [])
                     langargs[langname] = cargs + cti_args + args
@@ -1776,6 +1778,8 @@ def generate_single_build_target(self, objects_dict, target_name, target) -> Non
             settings_dict.add_item('SECTORDER_FLAGS', '')
             if is_swift and bridging_header:
                 settings_dict.add_item('SWIFT_OBJC_BRIDGING_HEADER', bridging_header)
+                if self.objversion >= 60 and 'cpp' in langs:
+                    settings_dict.add_item('SWIFT_OBJC_INTEROP_MODE', 'objcxx')
             settings_dict.add_item('BUILD_DIR', symroot)
             settings_dict.add_item('OBJROOT', f'{symroot}/build')
             sysheader_arr = PbxArray()

mesonbuild/compilers/swift.py

@@ -153,6 +153,12 @@ def get_working_directory_args(self, path: str) -> T.Optional[T.List[str]]:
 
         return ['-working-directory', path]
 
+    def get_cxx_interoperability_args(self, lang: T.Dict[str, Compiler]) -> T.List[str]:
+        if 'cpp' in lang or 'objcpp' in lang:
+            return ['-cxx-interoperability-mode=default']
+        else:
+            return ['-cxx-interoperability-mode=off']
+
     def compute_parameters_with_absolute_paths(self, parameter_list: T.List[str],
                                                build_dir: str) -> T.List[str]:
         for idx, i in enumerate(parameter_list):