Enhance Rust support

- Adds a `crate_type` kwarg to library targets, allowing the different
  types of Rust [linkage][1].
- Shared libraries use the `dylib` crate type by default, but can also
  be `cdylib`
- Static libraries use the `rlib` crate type by default, but can also
  be `staticlib`
- If any Rust target has shared library dependencies, add the
  appropriate linker arguments, including rpath for the sysroot of the
  Rust compiler

[1]: https://doc.rust-lang.org/reference/linkage.html

12 files changed, 117 insertions, 11 deletions

diff --git a/docs/markdown/Reference-manual.md b/docs/markdown/Reference-manual.md
index 492666b..61a66f0 100644
--- a/docs/markdown/Reference-manual.md
+++ b/docs/markdown/Reference-manual.md
@@ -510,11 +510,12 @@ Joins the given strings into a file system path segment. For example `join_paths
 
 Builds a library that is either static or shared depending on the value of `default_library` user option. You should use this instead of [`shared_library`](#shared_library) or [`static_library`](#static_library) most of the time. This allows you to toggle your entire project (including subprojects) from shared to static with only one option.
 
-The keyword arguments for this are the same as for [`executable`](#executable) with the following addition:
+The keyword arguments for this are the same as for [`executable`](#executable) with the following additions:
 
 - `name_prefix` the string that will be used as the suffix for the target by overriding the default (only used for libraries). By default this is `lib` on all platforms and compilers except with MSVC where it is omitted.
+- `crate_type` specifies the crate type for Rust libraries. Defaults to `dylib` for shared libraries and `rlib` for static libraries.
 
-`static_library` and `shared_library` also accept this keyword argument.
+`static_library` and `shared_library` also accept these keyword arguments.
 
 ### message()
 
diff --git a/mesonbuild/backend/ninjabackend.py b/mesonbuild/backend/ninjabackend.py
index 40a05bf..5764b54 100644
--- a/mesonbuild/backend/ninjabackend.py
+++ b/mesonbuild/backend/ninjabackend.py
@@ -1157,8 +1157,10 @@ int dummy;
         args = ['--crate-type']
         if isinstance(target, build.Executable):
             cratetype = 'bin'
+        elif hasattr(target, 'crate_type'):
+            cratetype = target.crate_type
         elif isinstance(target, build.SharedLibrary):
-            cratetype = 'rlib'
+            cratetype = 'dylib'
         elif isinstance(target, build.StaticLibrary):
             cratetype = 'rlib'
         else:
@@ -1177,6 +1179,23 @@ int dummy;
             if d == '':
                 d = '.'
             args += ['-L', d]
+        has_shared_deps = False
+        for dep in target.get_dependencies():
+            if isinstance(dep, build.SharedLibrary):
+                has_shared_deps = True
+        if isinstance(target, build.SharedLibrary) or has_shared_deps:
+            # add prefer-dynamic if any of the Rust libraries we link
+            # against are dynamic, otherwise we'll end up with
+            # multiple implementations of crates
+            args += ['-C', 'prefer-dynamic']
+            # build the usual rpath arguments as well...
+            rpath_args = rustc.build_rpath_args(self.environment.get_build_dir(),
+                                                self.determine_rpath_dirs(target),
+                                                target.install_rpath)
+            # ... but then add rustc's sysroot to account for rustup
+            # installations
+            for rpath_arg in rpath_args:
+                args += ['-C', 'link-arg=' + rpath_arg + ':' + os.path.join(rustc.get_sysroot(), 'lib')]
         element = NinjaBuildElement(self.all_outputs, target_name, 'rust_COMPILER', relsrc)
         if len(orderdeps) > 0:
             element.add_orderdep(orderdeps)
@@ -1184,6 +1203,8 @@ int dummy;
         element.add_item('targetdep', depfile)
         element.add_item('cratetype', cratetype)
         element.write(outfile)
+        if isinstance(target, build.SharedLibrary):
+            self.generate_shsym(outfile, target)
 
     def swift_module_file_name(self, target):
         return os.path.join(self.get_target_private_dir(target),
diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index 2c55ed4..f4b3382 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -71,6 +71,7 @@ known_lib_kwargs.update({'version': True, # Only for shared libs
                          'vala_vapi': True,
                          'vala_gir': True,
                          'pic': True, # Only for static libs
+                         'crate_type': True, # Only for Rust libs
                          })
 
 
@@ -1123,6 +1124,14 @@ class StaticLibrary(BuildTarget):
         super().__init__(name, subdir, subproject, is_cross, sources, objects, environment, kwargs)
         if 'cs' in self.compilers:
             raise InvalidArguments('Static libraries not supported for C#.')
+        if 'rust' in self.compilers:
+            # If no crate type is specified, or it's the generic lib type, use rlib
+            if not hasattr(self, 'crate_type') or self.crate_type == 'lib':
+                mlog.debug('Defaulting Rust static library target crate type to rlib')
+                self.crate_type = 'rlib'
+            # Don't let configuration proceed with a non-static crate type
+            elif self.crate_type not in ['rlib', 'staticlib']:
+                raise InvalidArguments('Crate type "{0}" invalid for static libraries; must be "rlib" or "staticlib"'.format(self.crate_type))
         # By default a static library is named libfoo.a even on Windows because
         # MSVC does not have a consistent convention for what static libraries
         # are called. The MSVC CRT uses libfoo.lib syntax but nothing else uses
@@ -1133,9 +1142,12 @@ class StaticLibrary(BuildTarget):
         if not hasattr(self, 'prefix'):
             self.prefix = 'lib'
         if not hasattr(self, 'suffix'):
-            # Rust static library crates have .rlib suffix
             if 'rust' in self.compilers:
-                self.suffix = 'rlib'
+                if not hasattr(self, 'crate_type') or self.crate_type == 'rlib':
+                    # default Rust static library suffix
+                    self.suffix = 'rlib'
+                elif self.crate_type == 'staticlib':
+                    self.suffix = 'a'
             else:
                 self.suffix = 'a'
         self.filename = self.prefix + self.name + '.' + self.suffix
@@ -1147,6 +1159,15 @@ class StaticLibrary(BuildTarget):
     def check_unknown_kwargs(self, kwargs):
         self.check_unknown_kwargs_int(kwargs, known_lib_kwargs)
 
+    def process_kwargs(self, kwargs, environment):
+        super().process_kwargs(kwargs, environment)
+        if 'crate_type' in kwargs:
+            crate_type = kwargs['crate_type']
+            if isinstance(crate_type, str):
+                self.crate_type = crate_type
+            else:
+                raise InvalidArguments('Invalid crate_type "{0}": must be a string.'.format(crate_type))
+
 class SharedLibrary(BuildTarget):
     def __init__(self, name, subdir, subproject, is_cross, sources, objects, environment, kwargs):
         self.soversion = None
@@ -1159,6 +1180,14 @@ class SharedLibrary(BuildTarget):
         # The import library that GCC would generate (and prefer)
         self.gcc_import_filename = None
         super().__init__(name, subdir, subproject, is_cross, sources, objects, environment, kwargs)
+        if 'rust' in self.compilers:
+            # If no crate type is specified, or it's the generic lib type, use dylib
+            if not hasattr(self, 'crate_type') or self.crate_type == 'lib':
+                mlog.debug('Defaulting Rust dynamic library target crate type to "dylib"')
+                self.crate_type = 'dylib'
+            # Don't let configuration proceed with a non-dynamic crate type
+            elif self.crate_type not in ['dylib', 'cdylib']:
+                raise InvalidArguments('Crate type "{0}" invalid for dynamic libraries; must be "dylib" or "cdylib"'.format(self.crate_type))
         if not hasattr(self, 'prefix'):
             self.prefix = None
         if not hasattr(self, 'suffix'):
@@ -1200,12 +1229,6 @@ class SharedLibrary(BuildTarget):
             prefix = ''
             suffix = 'dll'
             self.filename_tpl = '{0.prefix}{0.name}.{0.suffix}'
-        # Rust
-        elif 'rust' in self.compilers:
-            # Currently, we always build --crate-type=rlib
-            prefix = 'lib'
-            suffix = 'rlib'
-            self.filename_tpl = '{0.prefix}{0.name}.{0.suffix}'
         # C, C++, Swift, Vala
         # Only Windows uses a separate import library for linking
         # For all other targets/platforms import_filename stays None
@@ -1315,6 +1338,12 @@ class SharedLibrary(BuildTarget):
                 raise InvalidArguments(
                     'Shared library vs_module_defs must be either a string, '
                     'a file object or a Custom Target')
+        if 'crate_type' in kwargs:
+            crate_type = kwargs['crate_type']
+            if isinstance(crate_type, str):
+                self.crate_type = crate_type
+            else:
+                raise InvalidArguments('Invalid crate_type "{0}": must be a string.'.format(crate_type))
 
     def check_unknown_kwargs(self, kwargs):
         self.check_unknown_kwargs_int(kwargs, known_lib_kwargs)
diff --git a/mesonbuild/compilers.py b/mesonbuild/compilers.py
index c9cfb46..6e7283c 100644
--- a/mesonbuild/compilers.py
+++ b/mesonbuild/compilers.py
@@ -1809,6 +1809,14 @@ class RustCompiler(Compiler):
     def get_buildtype_args(self, buildtype):
         return rust_buildtype_args[buildtype]
 
+    def build_rpath_args(self, build_dir, rpath_paths, install_rpath):
+        return build_unix_rpath_args(build_dir, rpath_paths, install_rpath)
+
+    def get_sysroot(self):
+        cmd = self.exelist + ['--print', 'sysroot']
+        p, stdo, stde = Popen_safe(cmd)
+        return stdo.split('\n')[0]
+
 class SwiftCompiler(Compiler):
     def __init__(self, exelist, version):
         self.language = 'swift'
diff --git a/test cases/rust/4 polyglot/installed_files.txt b/test cases/rust/4 polyglot/installed_files.txt
new file mode 100644
index 0000000..680343d
--- /dev/null
+++ b/test cases/rust/4 polyglot/installed_files.txt
@@ -0,0 +1,2 @@
+usr/bin/prog?exe
+usr/lib/libstuff.so
diff --git a/test cases/rust/4 polyglot/meson.build b/test cases/rust/4 polyglot/meson.build
new file mode 100644
index 0000000..a20d766
--- /dev/null
+++ b/test cases/rust/4 polyglot/meson.build
@@ -0,0 +1,5 @@
+project('rust and c polyglot executable', 'c', 'rust')
+
+l = library('stuff', 'stuff.rs', install : true)
+e = executable('prog', 'prog.c', link_with : l, install : true)
+test('polyglottest', e)
diff --git a/test cases/rust/4 polyglot/prog.c b/test cases/rust/4 polyglot/prog.c
new file mode 100644
index 0000000..18f2c36
--- /dev/null
+++ b/test cases/rust/4 polyglot/prog.c
@@ -0,0 +1,8 @@
+#include <stdio.h>
+
+void f();
+
+int main() {
+    printf("Hello from C!\n");
+    f();
+}
diff --git a/test cases/rust/4 polyglot/stuff.rs b/test cases/rust/4 polyglot/stuff.rs
new file mode 100644
index 0000000..ecf623c
--- /dev/null
+++ b/test cases/rust/4 polyglot/stuff.rs
@@ -0,0 +1,6 @@
+#![crate_name = "stuff"]
+
+#[no_mangle]
+pub extern fn f() {
+    println!("Hello from Rust!");
+}
diff --git a/test cases/rust/5 polyglot static/installed_files.txt b/test cases/rust/5 polyglot static/installed_files.txt
new file mode 100644
index 0000000..2f7a397
--- /dev/null
+++ b/test cases/rust/5 polyglot static/installed_files.txt
@@ -0,0 +1,2 @@
+usr/bin/prog?exe
+usr/lib/libstuff.a
diff --git a/test cases/rust/5 polyglot static/meson.build b/test cases/rust/5 polyglot static/meson.build
new file mode 100644
index 0000000..8eb2d53
--- /dev/null
+++ b/test cases/rust/5 polyglot static/meson.build
@@ -0,0 +1,10 @@
+project('static rust and c polyglot executable', 'c', 'rust')
+
+deps = [
+  meson.get_compiler('c').find_library('dl'),
+  dependency('threads'),
+]
+
+l = static_library('stuff', 'stuff.rs', crate_type : 'staticlib', install : true)
+e = executable('prog', 'prog.c', dependencies: deps, link_with : l, install : true)
+test('polyglottest', e)
diff --git a/test cases/rust/5 polyglot static/prog.c b/test cases/rust/5 polyglot static/prog.c
new file mode 100644
index 0000000..18f2c36
--- /dev/null
+++ b/test cases/rust/5 polyglot static/prog.c
@@ -0,0 +1,8 @@
+#include <stdio.h>
+
+void f();
+
+int main() {
+    printf("Hello from C!\n");
+    f();
+}
diff --git a/test cases/rust/5 polyglot static/stuff.rs b/test cases/rust/5 polyglot static/stuff.rs
new file mode 100644
index 0000000..ecf623c
--- /dev/null
+++ b/test cases/rust/5 polyglot static/stuff.rs
@@ -0,0 +1,6 @@
+#![crate_name = "stuff"]
+
+#[no_mangle]
+pub extern fn f() {
+    println!("Hello from Rust!");
+}