rust: allow linking with dynamic libstd

docs/markdown/Builtin-options.md

@@ -290,6 +290,7 @@ or compiler being used:
 | cpp_thread_count | 4             | integer value ≥ 0                        | Number of threads to use with emcc when using threads |
 | cpp_winlibs      | see below     | free-form comma-separated list           | Standard Windows libs to link against |
 | fortran_std      | none          | [none, legacy, f95, f2003, f2008, f2018] | Fortran language standard to use |
+| rust_dynamic_std | false         | true, false                              | Whether to link dynamically to the Rust standard library *(Added in 1.8.0)* |
 | cuda_ccbindir    |               | filesystem path                          | CUDA non-default toolchain directory to use (-ccbin) *(Added in 0.57.1)* |
 
 The default values of `c_winlibs` and `cpp_winlibs` are in

docs/markdown/snippets/rust-dynamic-std.md

@@ -0,0 +1,7 @@
+## New experimental option `rust_dynamic_std`
+
+A new option `rust_dynamic_std` can be used to link Rust programs so
+that they use a dynamic library for the Rust `libstd`.
+
+Right now, `staticlib` crates cannot be produced if `rust_dynamic_std` is
+true, but this may change in the future.

mesonbuild/backend/ninjabackend.py

@@ -2116,13 +2116,26 @@ def _link_library(libname: str, static: bool, bundle: bool = False):
                                    and dep.rust_crate_type == 'dylib'
                                    for dep in target_deps)
 
-        if target.rust_crate_type in {'dylib', 'proc-macro'} or has_rust_shared_deps:
+        if target.rust_crate_type == 'staticlib' \
+                and self.get_target_option(target, 'rust_dynamic_std'):
+            # staticlib crates always include a copy of the Rust libstd,
+            # therefore it is not possible to also link it dynamically.
+            # The options to avoid this (-Z staticlib-allow-rdylib-deps and
+            # -Z staticlib-prefer-dynamic) are not yet stable; alternatively,
+            # one could use "--emit obj" (implemented in the pull request at
+            # https://github.com/mesonbuild/meson/pull/11213) or "--emit rlib"
+            # (officially not recommended for linking with C programs).
+            raise MesonException('rust_dynamic_std does not support staticlib crates yet')
+
+        if target.rust_crate_type in {'dylib', 'proc-macro'} or has_rust_shared_deps \
+                or self.get_target_option(target, 'rust_dynamic_std'):
             # add prefer-dynamic if any of the Rust libraries we link
             # against are dynamic or this is a dynamic library itself,
             # otherwise we'll end up with multiple implementations of libstd.
             args += ['-C', 'prefer-dynamic']
 
-        if isinstance(target, build.SharedLibrary) or has_shared_deps:
+        if isinstance(target, build.SharedLibrary) or has_shared_deps \
+                or self.get_target_option(target, 'rust_dynamic_std'):
             args += self.get_build_rpath_args(target, rustc)
 
         proc_macro_dylib_path = None

mesonbuild/compilers/rust.py

@@ -203,15 +203,15 @@ def get_optimization_args(self, optimization_level: str) -> T.List[str]:
     def build_rpath_args(self, env: 'Environment', build_dir: str, from_dir: str,
                          rpath_paths: T.Tuple[str, ...], build_rpath: str,
                          install_rpath: str) -> T.Tuple[T.List[str], T.Set[bytes]]:
-        args, to_remove = super().build_rpath_args(env, build_dir, from_dir, rpath_paths,
-                                                   build_rpath, install_rpath)
+        # add rustc's sysroot to account for rustup installations
+        args, to_remove = self.linker.build_rpath_args(env, build_dir, from_dir, rpath_paths,
+                                                       build_rpath, install_rpath,
+                                                       [self.get_target_libdir()])
 
-        # ... but then add rustc's sysroot to account for rustup
-        # installations
         rustc_rpath_args = []
         for arg in args:
             rustc_rpath_args.append('-C')
-            rustc_rpath_args.append(f'link-arg={arg}:{self.get_target_libdir()}')
+            rustc_rpath_args.append('link-arg=' + arg)
         return rustc_rpath_args, to_remove
 
     def compute_parameters_with_absolute_paths(self, parameter_list: T.List[str],
@@ -244,6 +244,12 @@ def get_options(self) -> MutableKeyedOptionDictType:
             'none',
             choices=['none', '2015', '2018', '2021', '2024'])
 
+        key = self.form_compileropt_key('dynamic_std')
+        opts[key] = options.UserBooleanOption(
+            self.make_option_name(key),
+            'Whether to link Rust build targets to a dynamic libstd',
+            False)
+
         return opts
 
     def get_dependency_compile_args(self, dep: 'Dependency') -> T.List[str]:

mesonbuild/linkers/linkers.py

@@ -63,7 +63,7 @@ def get_coverage_link_args(self) -> T.List[str]:
 
     def build_rpath_args(self, env: 'Environment', build_dir: str, from_dir: str,
                          rpath_paths: T.Tuple[str, ...], build_rpath: str,
-                         install_rpath: str) -> T.Tuple[T.List[str], T.Set[bytes]]:
+                         install_rpath: str, extra_paths: T.Optional[T.List[str]] = None) -> T.Tuple[T.List[str], T.Set[bytes]]:
         return ([], set())
 
     def thread_link_flags(self, env: 'Environment') -> T.List[str]:
@@ -290,7 +290,7 @@ def bitcode_args(self) -> T.List[str]:
 
     def build_rpath_args(self, env: 'Environment', build_dir: str, from_dir: str,
                          rpath_paths: T.Tuple[str, ...], build_rpath: str,
-                         install_rpath: str) -> T.Tuple[T.List[str], T.Set[bytes]]:
+                         install_rpath: str, extra_paths: T.Optional[T.List[str]] = None) -> T.Tuple[T.List[str], T.Set[bytes]]:
         return ([], set())
 
     def get_soname_args(self, env: 'Environment', prefix: str, shlib_name: str,
@@ -693,11 +693,11 @@ def get_soname_args(self, env: 'Environment', prefix: str, shlib_name: str,
 
     def build_rpath_args(self, env: 'Environment', build_dir: str, from_dir: str,
                          rpath_paths: T.Tuple[str, ...], build_rpath: str,
-                         install_rpath: str) -> T.Tuple[T.List[str], T.Set[bytes]]:
+                         install_rpath: str, extra_paths: T.Optional[T.List[str]] = None) -> T.Tuple[T.List[str], T.Set[bytes]]:
         m = env.machines[self.for_machine]
         if m.is_windows() or m.is_cygwin():
             return ([], set())
-        if not rpath_paths and not install_rpath and not build_rpath:
+        if not rpath_paths and not install_rpath and not build_rpath and not extra_paths:
             return ([], set())
         args: T.List[str] = []
         origin_placeholder = '$ORIGIN'
@@ -714,6 +714,8 @@ def build_rpath_args(self, env: 'Environment', build_dir: str, from_dir: str,
             all_paths.add(build_rpath)
             for p in build_rpath.split(':'):
                 rpath_dirs_to_remove.add(p.encode('utf8'))
+        if extra_paths:
+            all_paths.update(extra_paths)
 
         # TODO: should this actually be "for (dragonfly|open)bsd"?
         if mesonlib.is_dragonflybsd() or mesonlib.is_openbsd():
@@ -850,8 +852,8 @@ def get_soname_args(self, env: 'Environment', prefix: str, shlib_name: str,
 
     def build_rpath_args(self, env: 'Environment', build_dir: str, from_dir: str,
                          rpath_paths: T.Tuple[str, ...], build_rpath: str,
-                         install_rpath: str) -> T.Tuple[T.List[str], T.Set[bytes]]:
-        if not rpath_paths and not install_rpath and not build_rpath:
+                         install_rpath: str, extra_paths: T.Optional[T.List[str]] = None) -> T.Tuple[T.List[str], T.Set[bytes]]:
+        if not rpath_paths and not install_rpath and not build_rpath and not extra_paths:
             return ([], set())
         args: T.List[str] = []
         rpath_dirs_to_remove: T.Set[bytes] = set()
@@ -862,6 +864,8 @@ def build_rpath_args(self, env: 'Environment', build_dir: str, from_dir: str,
         all_paths = mesonlib.OrderedSet([os.path.join(origin_placeholder, p) for p in processed_rpaths])
         if build_rpath != '':
             all_paths.update(build_rpath.split(':'))
+        if extra_paths:
+            all_paths.update(extra_paths)
         for rp in all_paths:
             rpath_dirs_to_remove.add(rp.encode('utf8'))
             args.extend(self._apply_prefix('-rpath,' + rp))
@@ -998,7 +1002,7 @@ def get_asneeded_args(self) -> T.List[str]:
 
     def build_rpath_args(self, env: 'Environment', build_dir: str, from_dir: str,
                          rpath_paths: T.Tuple[str, ...], build_rpath: str,
-                         install_rpath: str) -> T.Tuple[T.List[str], T.Set[bytes]]:
+                         install_rpath: str, extra_paths: T.Optional[T.List[str]] = None) -> T.Tuple[T.List[str], T.Set[bytes]]:
         return ([], set())
 
 
@@ -1076,7 +1080,7 @@ def get_soname_args(self, env: 'Environment', prefix: str, shlib_name: str,
 
     def build_rpath_args(self, env: 'Environment', build_dir: str, from_dir: str,
                          rpath_paths: T.Tuple[str, ...], build_rpath: str,
-                         install_rpath: str) -> T.Tuple[T.List[str], T.Set[bytes]]:
+                         install_rpath: str, extra_paths: T.Optional[T.List[str]] = None) -> T.Tuple[T.List[str], T.Set[bytes]]:
         return ([], set())
 
 class CompCertDynamicLinker(DynamicLinker):
@@ -1119,7 +1123,7 @@ def get_soname_args(self, env: 'Environment', prefix: str, shlib_name: str,
 
     def build_rpath_args(self, env: 'Environment', build_dir: str, from_dir: str,
                          rpath_paths: T.Tuple[str, ...], build_rpath: str,
-                         install_rpath: str) -> T.Tuple[T.List[str], T.Set[bytes]]:
+                         install_rpath: str, extra_paths: T.Optional[T.List[str]] = None) -> T.Tuple[T.List[str], T.Set[bytes]]:
         return ([], set())
 
 class TIDynamicLinker(DynamicLinker):
@@ -1225,15 +1229,17 @@ class NAGDynamicLinker(PosixDynamicLinkerMixin, DynamicLinker):
 
     def build_rpath_args(self, env: 'Environment', build_dir: str, from_dir: str,
                          rpath_paths: T.Tuple[str, ...], build_rpath: str,
-                         install_rpath: str) -> T.Tuple[T.List[str], T.Set[bytes]]:
-        if not rpath_paths and not install_rpath and not build_rpath:
+                         install_rpath: str, extra_paths: T.Optional[T.List[str]] = None) -> T.Tuple[T.List[str], T.Set[bytes]]:
+        if not rpath_paths and not install_rpath and not build_rpath and not extra_paths:
             return ([], set())
         args: T.List[str] = []
         origin_placeholder = '$ORIGIN'
         processed_rpaths = prepare_rpaths(rpath_paths, build_dir, from_dir)
         all_paths = mesonlib.OrderedSet([os.path.join(origin_placeholder, p) for p in processed_rpaths])
         if build_rpath != '':
             all_paths.add(build_rpath)
+        if extra_paths:
+            all_paths.update(extra_paths)
         for rp in all_paths:
             args.extend(self._apply_prefix('-Wl,-Wl,,-rpath,,' + rp))
 
@@ -1270,7 +1276,7 @@ def get_std_shared_lib_args(self) -> T.List[str]:
 
     def build_rpath_args(self, env: 'Environment', build_dir: str, from_dir: str,
                          rpath_paths: T.Tuple[str, ...], build_rpath: str,
-                         install_rpath: str) -> T.Tuple[T.List[str], T.Set[bytes]]:
+                         install_rpath: str, extra_paths: T.Optional[T.List[str]] = None) -> T.Tuple[T.List[str], T.Set[bytes]]:
         if not env.machines[self.for_machine].is_windows():
             return (['-R' + os.path.join(build_dir, p) for p in rpath_paths], set())
         return ([], set())
@@ -1481,8 +1487,8 @@ def fatal_warnings(self) -> T.List[str]:
 
     def build_rpath_args(self, env: 'Environment', build_dir: str, from_dir: str,
                          rpath_paths: T.Tuple[str, ...], build_rpath: str,
-                         install_rpath: str) -> T.Tuple[T.List[str], T.Set[bytes]]:
-        if not rpath_paths and not install_rpath and not build_rpath:
+                         install_rpath: str, extra_paths: T.Optional[T.List[str]] = None) -> T.Tuple[T.List[str], T.Set[bytes]]:
+        if not rpath_paths and not install_rpath and not build_rpath and not extra_paths:
             return ([], set())
         processed_rpaths = prepare_rpaths(rpath_paths, build_dir, from_dir)
         all_paths = mesonlib.OrderedSet([os.path.join('$ORIGIN', p) for p in processed_rpaths])
@@ -1493,6 +1499,8 @@ def build_rpath_args(self, env: 'Environment', build_dir: str, from_dir: str,
             all_paths.add(build_rpath)
             for p in build_rpath.split(':'):
                 rpath_dirs_to_remove.add(p.encode('utf8'))
+        if extra_paths:
+            all_paths.update(extra_paths)
 
         # In order to avoid relinking for RPATH removal, the binary needs to contain just
         # enough space in the ELF header to hold the final installation RPATH.
@@ -1551,7 +1559,7 @@ def get_link_whole_for(self, args: T.List[str]) -> T.List[str]:
 
     def build_rpath_args(self, env: 'Environment', build_dir: str, from_dir: str,
                          rpath_paths: T.Tuple[str, ...], build_rpath: str,
-                         install_rpath: str) -> T.Tuple[T.List[str], T.Set[bytes]]:
+                         install_rpath: str, extra_paths: T.Optional[T.List[str]] = None) -> T.Tuple[T.List[str], T.Set[bytes]]:
         all_paths: mesonlib.OrderedSet[str] = mesonlib.OrderedSet()
         # install_rpath first, followed by other paths, and the system path last
         if install_rpath != '':
@@ -1572,6 +1580,8 @@ def build_rpath_args(self, env: 'Environment', build_dir: str, from_dir: str,
             for p in sys_path:
                 if os.path.isdir(p):
                     all_paths.add(p)
+        if extra_paths:
+            all_paths.update(extra_paths)
         return (self._apply_prefix('-blibpath:' + ':'.join(all_paths)), set())
 
     def thread_flags(self, env: 'Environment') -> T.List[str]:

test cases/rust/1 basic/meson.build

@@ -6,6 +6,12 @@ e = executable('rust-program', 'prog.rs',
 )
 test('rusttest', e)
 
+e = executable('rust-dynamic', 'prog.rs',
+  override_options: {'rust_dynamic_std': true},
+  install : true
+)
+test('rusttest-dynamic', e)
+
 subdir('subdir')
 
 # this should fail due to debug_assert

test cases/rust/1 basic/test.json

@@ -3,6 +3,8 @@
     {"type": "exe", "file": "usr/bin/rust-program"},
     {"type": "pdb", "file": "usr/bin/rust-program"},
     {"type": "exe", "file": "usr/bin/rust-program2"},
-    {"type": "pdb", "file": "usr/bin/rust-program2"}
+    {"type": "pdb", "file": "usr/bin/rust-program2"},
+    {"type": "exe", "file": "usr/bin/rust-dynamic"},
+    {"type": "pdb", "file": "usr/bin/rust-dynamic"}
   ]
 }