rust: search for native static libs in target libdir

Sometimes, a Rust static library's native static libs refer to
libraries installed in the rustc target libdir.  This is always the
case for most musl targets (with the intention of making it easier to
use them on non-musl systems), and other targets can also be
configured to do this using e.g. the llvm-libunwind option when
building the standard libraries for the target.  When rustc is
responsible for linking it will always add the appropriate directory
to the linker search path, but if we're not using Rust for linking, we
have to tell the linker about that directory ourselves.

The added test demonstrates a scenario where this comes up: linking a
static Rust library, built for musl, into a C executable.  -lunwind is
in the native static libs list from the compiler, but it's referring
to the libunwind.a in the self-contained directory.

5 files changed, 36 insertions, 2 deletions

diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index a43709342..0ad679450 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -2327,8 +2327,9 @@ class StaticLibrary(BuildTarget):
                 #  and thus, machine_info kernel should be set to 'none'.
                 #  In that case, native_static_libs list is empty.
                 rustc = self.compilers['rust']
-                d = dependencies.InternalDependency('undefined', [], [],
-                                                    rustc.native_static_libs,
+                link_args = ['-L' + rustc.get_target_libdir() + '/self-contained']
+                link_args += rustc.native_static_libs
+                d = dependencies.InternalDependency('undefined', [], [], link_args,
                                                     [], [], [], [], [], {}, [], [], [],
                                                     '_rust_native_static_libs')
                 self.external_deps.append(d)
diff --git a/test cases/rust/28 self-contained/lib.rs b/test cases/rust/28 self-contained/lib.rs
new file mode 100644
index 000000000..f8a8bf201
--- /dev/null
+++ b/test cases/rust/28 self-contained/lib.rs
@@ -0,0 +1,4 @@
+#[unsafe(export_name = "hello")]
+pub extern "C" fn hello() {
+    println!("Hello, world!");
+}
diff --git a/test cases/rust/28 self-contained/main.c b/test cases/rust/28 self-contained/main.c
new file mode 100644
index 000000000..11bedf5ae
--- /dev/null
+++ b/test cases/rust/28 self-contained/main.c
@@ -0,0 +1,6 @@
+extern void hello(void);
+
+int main(void)
+{
+    hello();
+}
diff --git a/test cases/rust/28 self-contained/meson.build b/test cases/rust/28 self-contained/meson.build
new file mode 100644
index 000000000..25de68f25
--- /dev/null
+++ b/test cases/rust/28 self-contained/meson.build
@@ -0,0 +1,17 @@
+project('self-contained', meson_version : '>= 1.3.0')
+
+if not add_languages('c', native : false, required : false)
+  error('MESON_SKIP_TEST clang not installed')
+endif
+
+if not add_languages('rust', native : false, required : false)
+  error('MESON_SKIP_TEST Rust x86_64-unknown-linux-musl target not installed')
+endif
+
+if meson.get_compiler('c').find_library('libunwind', required : false).found()
+  error('MESON_SKIP_TEST libunwind is installed globally')
+endif
+
+lib = static_library('rust', 'lib.rs', rust_abi : 'c')
+
+executable('exe', 'main.c', link_with : lib)
diff --git a/test cases/rust/28 self-contained/test.json b/test cases/rust/28 self-contained/test.json
new file mode 100644
index 000000000..fccefd6f1
--- /dev/null
+++ b/test cases/rust/28 self-contained/test.json
@@ -0,0 +1,6 @@
+{
+  "env": {
+    "CC": "clang -target x86_64-unknown-linux-musl",
+    "RUSTC": "rustc --target x86_64-unknown-linux-musl"
+  }
+}