rust/bindgen: Use Meson rules for C++ headers

Bindgen natively only considers .hpp to be C++ headers, but Meson
considers some additional extensions including .hh and .hxx to be C++.

docs/markdown/snippets/rust-bindgen-cpp.md

@@ -0,0 +1,6 @@
+## Bindgen will now use Meson's hueristic for what is a C++ header
+
+Bindgen natively assumes that a file with the extension `.cpp` is a C++ header,
+but that everything else is a C header. Meson has a whole list of extensions it
+considers to be C++, and now will automatically look for those extensions and
+set bindgen to treat those as C++

mesonbuild/modules/rust.py

@@ -12,7 +12,7 @@ from . import ExtensionModule, ModuleReturnValue, ModuleInfo
 from .. import mlog
 from ..build import (BothLibraries, BuildTarget, CustomTargetIndex, Executable, ExtractedObjects, GeneratedList,
                      CustomTarget, InvalidArguments, Jar, StructuredSources, SharedLibrary)
-from ..compilers.compilers import are_asserts_disabled
+from ..compilers.compilers import are_asserts_disabled, lang_suffixes
 from ..interpreter.type_checking import DEPENDENCIES_KW, LINK_WITH_KW, SHARED_LIB_KWS, TEST_KWS, OUTPUT_KW, INCLUDE_DIRECTORIES, SOURCES_VARARGS
 from ..interpreterbase import ContainerTypeInfo, InterpreterException, KwargInfo, typed_kwargs, typed_pos_args, noPosargs, permittedKwargs
 from ..mesonlib import File
@@ -230,13 +230,6 @@ class RustModule(ExtensionModule):
                 elif isinstance(s, CustomTarget):
                     depends.append(s)
 
-        # We only want include directories and defines, other things may not be valid
-        cargs = state.get_option('args', state.subproject, lang='c')
-        assert isinstance(cargs, list), 'for mypy'
-        for a in itertools.chain(state.global_args.get('c', []), state.project_args.get('c', []), cargs):
-            if a.startswith(('-I', '/I', '-D', '/D', '-U', '/U')):
-                clang_args.append(a)
-
         if self._bindgen_bin is None:
             self._bindgen_bin = state.find_program('bindgen')
 
@@ -248,6 +241,22 @@ class RustModule(ExtensionModule):
         else:
             name = header.get_outputs()[0]
 
+        # bindgen assumes that C++ headers will be called .hpp. We want to
+        # ensure that anything Meson considers a C++ header is treated as one.
+        language = 'cpp' if os.path.splitext(name)[1][1:] in lang_suffixes['cpp'] else 'c'
+
+        # We only want include directories and defines, other things may not be valid
+        cargs = state.get_option('args', state.subproject, lang=language)
+        assert isinstance(cargs, list), 'for mypy'
+        for a in itertools.chain(state.global_args.get(language, []), state.project_args.get(language, []), cargs):
+            if a.startswith(('-I', '/I', '-D', '/D', '-U', '/U')):
+                clang_args.append(a)
+
+        # bindgen assumes that C++ headers will be called .hpp. We want to
+        # ensure that anything Meson considers a C++ header is treated as one.
+        if language == 'cpp':
+            clang_args.extend(['-x', 'c++'])
+
         cmd = self._bindgen_bin.get_command() + \
             [
                 '@INPUT@', '--output',

test cases/rust/12 bindgen/meson.build

@@ -1,7 +1,7 @@
 # SPDX-license-identifer: Apache-2.0
 # Copyright © 2021-2022 Intel Corporation
 
-project('rustmod bindgen', ['c', 'rust'], meson_version : '>= 0.63')
+project('rustmod bindgen', ['c', 'cpp', 'rust'], meson_version : '>= 0.63')
 
 prog_bindgen = find_program('bindgen', required : false)
 if not prog_bindgen.found()
@@ -107,3 +107,17 @@ gp_exe = executable(
 )
 
 test('global and project arguments', gp_exe)
+
+cpp_lib = static_library('cpplib', 'src/impl.cpp')
+
+cpp_bind = rust.bindgen(
+  input : 'src/header.hpp',
+  output : 'generated-cpp.rs',
+)
+
+cpp_exe = executable(
+  'cpp_exe',
+  structured_sources(['src/cpp.rs', cpp_bind]),
+  link_with : cpp_lib,
+)
+test('cpp', cpp_exe)

test cases/rust/12 bindgen/src/cpp.rs

@@ -0,0 +1,19 @@
+// SPDX-license-identifer: Apache-2.0
+// Copyright © 2023 Intel Corporation
+
+#![allow(non_upper_case_globals)]
+#![allow(non_camel_case_types)]
+#![allow(non_snake_case)]
+
+include!("generated-cpp.rs");
+
+fn main() {
+    let mut instance = std::mem::MaybeUninit::<MyClass>::uninit();
+    let val: i32;
+    unsafe {
+        MyClass_MyClass(instance.as_mut_ptr());
+        val = instance.assume_init_mut().method();
+    }
+    let success = val == 7;
+    std::process::exit(!success as i32);
+}

test cases/rust/12 bindgen/src/header.hpp

@@ -0,0 +1,9 @@
+#pragma once
+
+class MyClass {
+  public:
+    MyClass();
+    int method() const;
+  private:
+    int val;
+};

test cases/rust/12 bindgen/src/impl.cpp

@@ -0,0 +1,7 @@
+#include "header.hpp"
+
+MyClass::MyClass() : val{7} {};
+
+int MyClass::method() const {
+    return val;
+}