rust: Do not bundle static libraries into internal libraries

When a Rust rlib/staticlib links to a C static library, it should not
bundle its object files, unless it gets installed. This solves cases of
multiple symbol definition when there is a diamond dependency graph.

mesonbuild/backend/ninjabackend.py

@@ -1968,7 +1968,7 @@ def generate_rust_target(self, target: build.BuildTarget) -> None:
         # have to hope that the default cases of +whole-archive are sufficient.
         # See: https://github.com/rust-lang/rust/issues/99429
         if mesonlib.version_compare(rustc.version, '>= 1.63.0'):
-            whole_archive = '+whole-archive,-bundle'
+            whole_archive = '+whole-archive'
         else:
             whole_archive = ''
 
@@ -1978,6 +1978,15 @@ def generate_rust_target(self, target: build.BuildTarget) -> None:
         else:
             verbatim = ''
 
+        def add_native_library(libname: str, static: bool, modifiers: T.Optional[T.List[str]] = None):
+            _type = 'static' if static else 'dylib'
+            modifiers = modifiers or []
+            if static and target.is_internal():
+                modifiers.append('-bundle')
+            if modifiers:
+                _type += ':' + ','.join(modifiers)
+            args.extend(['-l', f'{_type}={libname}'])
+
         linkdirs = mesonlib.OrderedSet()
         external_deps = target.external_deps.copy()
         target_deps = target.get_dependencies()
@@ -2034,10 +2043,8 @@ def generate_rust_target(self, target: build.BuildTarget) -> None:
                     need_link = False
 
             if need_link:
-                _type = 'static' if isinstance(d, build.StaticLibrary) else 'dylib'
-                if modifiers:
-                    _type += ':' + ','.join(modifiers)
-                args += ['-l', f'{_type}={os.path.basename(lib)}']
+                static = isinstance(d, build.StaticLibrary)
+                add_native_library(os.path.basename(lib), static, modifiers)
 
         for e in external_deps:
             for a in e.get_link_args():
@@ -2050,13 +2057,13 @@ def generate_rust_target(self, target: build.BuildTarget) -> None:
                     lib, ext = os.path.splitext(lib)
                     if lib.startswith('lib'):
                         lib = lib[3:]
-                    _type = 'static' if a.endswith(('.a', '.lib')) else 'dylib'
-                    args.extend(['-l', f'{_type}={lib}'])
+                    static = a.endswith(('.a', '.lib'))
+                    add_native_library(lib, static)
                 elif a.startswith('-L'):
                     args.append(a)
                 elif a.startswith('-l'):
-                    _type = 'static' if e.static else 'dylib'
-                    args.extend(['-l', f'{_type}={a[2:]}'])
+                    static = a.endswith(('.a', '.lib'))
+                    add_native_library(a[2:], e.static)
         for d in linkdirs:
             if d == '':
                 d = '.'

test cases/rust/20 transitive dependencies/diamond/func.c

@@ -0,0 +1,4 @@
+int c_func(void);
+int c_func(void) {
+    return 123;
+}

test cases/rust/20 transitive dependencies/diamond/main.c

@@ -0,0 +1,5 @@
+int r3(void);
+
+int main_func(void) {
+    return r3() == 246 ? 0 : 1;
+}

test cases/rust/20 transitive dependencies/diamond/meson.build

@@ -0,0 +1,25 @@
+# Regression test for a diamond dependency graph:
+#          ┌►R1┐
+# main-►R3─┤   ├─►C1
+#          └►R2┘
+# Both libr1.rlib and libr2.rlib used to contain func.c.o. That was causing
+# libr3.rlib to have duplicated func.c.o and then libmain.so failed to link:
+# multiple definition of `c_func'.
+
+libc1 = static_library('c1', 'func.c')
+libr1 = static_library('r1', 'r1.rs', link_with: libc1)
+libr2 = static_library('r2', 'r2.rs', link_with: libc1)
+libr3 = static_library('r3', 'r3.rs',
+  link_with: [libr1, libr2],
+  rust_abi: 'c',
+)
+shared_library('main', 'main.c', link_whole: [libr3])
+
+# Same dependency graph, but r3 is now installed. Since c1, r1 and r2 are
+# not installed, r3 must contain them.
+libr3 = static_library('r3-installed', 'r3.rs',
+  link_with: [libr1, libr2],
+  rust_abi: 'c',
+  install: true,
+)
+shared_library('main-installed', 'main.c', link_with: [libr3])

test cases/rust/20 transitive dependencies/diamond/r1.rs

@@ -0,0 +1,9 @@
+extern "C" {
+    fn c_func() -> i32;
+}
+
+pub fn r1() -> i32 {
+    unsafe {
+        c_func()
+    }
+}

test cases/rust/20 transitive dependencies/diamond/r2.rs

@@ -0,0 +1,9 @@
+extern "C" {
+    fn c_func() -> i32;
+}
+
+pub fn r2() -> i32 {
+    unsafe {
+        c_func()
+    }
+}

test cases/rust/20 transitive dependencies/diamond/r3.rs

@@ -0,0 +1,4 @@
+#[no_mangle]
+pub fn r3() -> i32 {
+    r1::r1() + r2::r2()
+}

test cases/rust/20 transitive dependencies/meson.build

@@ -25,3 +25,5 @@ exe = executable('footest', 'foo.c',
   link_with: foo,
 )
 test('footest', exe)
+
+subdir('diamond')