rust: get stdlib arguments for non-rust languages when linking

Otherwise we might not get things like libstdc++, which we need.

mesonbuild/backend/ninjabackend.py

@@ -2040,6 +2040,11 @@ class NinjaBackend(backends.Backend):
             if d == '':
                 d = '.'
             args += ['-L', d]
+
+        # Because of the way rustc links, this must come after any potential
+        # library need to link with their stdlibs (C++ and Fortran, for example)
+        args.extend(target.get_used_stdlib_args('rust'))
+
         target_deps = target.get_dependencies()
         has_shared_deps = any(isinstance(dep, build.SharedLibrary) for dep in target_deps)
         has_rust_shared_deps = any(dep.uses_rust()

mesonbuild/build.py

@@ -698,6 +698,15 @@ class BuildTarget(Target):
 
     install_dir: T.List[T.Union[str, Literal[False]]]
 
+    # This set contains all the languages a linker can link natively
+    # without extra flags. For instance, nvcc (cuda) can link C++
+    # without injecting -lc++/-lstdc++, see
+    #   https://github.com/mesonbuild/meson/issues/10570
+    _MASK_LANGS: T.FrozenSet[T.Tuple[str, str]] = frozenset([
+        # (language, linker)
+        ('cpp', 'cuda'),
+    ])
+
     def __init__(
             self,
             name: str,
@@ -1579,14 +1588,6 @@ You probably should put it in link_with instead.''')
         # Languages used by dependencies
         dep_langs = self.get_langs_used_by_deps()
 
-        # This set contains all the languages a linker can link natively
-        # without extra flags. For instance, nvcc (cuda) can link C++
-        # without injecting -lc++/-lstdc++, see
-        #   https://github.com/mesonbuild/meson/issues/10570
-        MASK_LANGS = frozenset([
-            # (language, linker)
-            ('cpp', 'cuda'),
-        ])
         # Pick a compiler based on the language priority-order
         for l in clink_langs:
             if l in self.compilers or l in dep_langs:
@@ -1597,10 +1598,7 @@ You probably should put it in link_with instead.''')
                         f'Could not get a dynamic linker for build target {self.name!r}. '
                         f'Requires a linker for language "{l}", but that is not '
                         'a project language.')
-                stdlib_args: T.List[str] = []
-                for dl in itertools.chain(self.compilers, dep_langs):
-                    if dl != linker.language and (dl, linker.language) not in MASK_LANGS:
-                        stdlib_args += all_compilers[dl].language_stdlib_only_link_flags(self.environment)
+                stdlib_args: T.List[str] = self.get_used_stdlib_args(linker.language)
                 # Type of var 'linker' is Compiler.
                 # Pretty hard to fix because the return value is passed everywhere
                 return linker, stdlib_args
@@ -1616,6 +1614,15 @@ You probably should put it in link_with instead.''')
 
         raise AssertionError(f'Could not get a dynamic linker for build target {self.name!r}')
 
+    def get_used_stdlib_args(self, link_language: str) -> T.List[str]:
+        all_compilers = self.environment.coredata.compilers[self.for_machine]
+        all_langs = set(all_compilers).union(self.get_langs_used_by_deps())
+        stdlib_args: T.List[str] = []
+        for dl in all_langs:
+            if dl != link_language and (dl, link_language) not in self._MASK_LANGS:
+                stdlib_args.extend(all_compilers[dl].language_stdlib_only_link_flags(self.environment))
+        return stdlib_args
+
     def uses_rust(self) -> bool:
         return 'rust' in self.compilers
 

test cases/rust/20 rust and cpp/lib.cpp

@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright © 2023 Intel Corporation
+
+#include "lib.hpp"
+
+#include <string>
+
+namespace {
+
+uint64_t priv_length(const std::string & str) {
+    return str.length();
+}
+
+}
+
+extern "C" uint64_t lib_length(const char * str) {
+    return priv_length(str);
+}

test cases/rust/20 rust and cpp/lib.hpp

@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright © 2023 Intel Corporation
+
+#include <cstddef>
+#include <cstdint>
+
+extern "C" uint64_t lib_length(const char * str);
+

test cases/rust/20 rust and cpp/main.rs

@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright © 2023 Intel Corporation
+
+use std::ffi::CString;
+use std::os::raw::c_char;
+
+extern "C" {
+        fn lib_length(s: *const c_char) -> u64;
+}
+
+fn main() {
+        let len: u64;
+        unsafe {
+                let c_str = CString::new("Hello, world!").unwrap();
+                len = lib_length(c_str.as_ptr());
+        }
+
+        std::process::exit(if len == 13 { 0 } else { 1 })
+}

test cases/rust/20 rust and cpp/meson.build

@@ -0,0 +1,14 @@
+# SPDX-License-Identifier: Apache-2.0
+# Copyright © 2023 Intel Corporation
+
+project(
+  'Rust and C++',
+  'rust', 'cpp',
+  default_options : ['cpp_std=c++14'],
+  meson_version : '>= 1.2.0',
+)
+
+cpplib = static_library('cpp', 'lib.cpp')
+exe = executable('main', 'main.rs', link_with : cpplib)
+
+test('main', exe)