rust: make declaration of dependent crates more consistent

Crates like "bilge" and "libc" can be shared by more than one directory,
so declare them directly in rust/meson.build.  While at it, make their
variable names end with "_rs" and always add a subproject() statement
(as that pinpoints the error better if the subproject is missing and
cannot be downloaded).

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

rust/hw/char/pl011/meson.build

@@ -1,17 +1,11 @@
-subproject('bilge-0.2-rs', required: true)
-subproject('bilge-impl-0.2-rs', required: true)
-
-bilge_dep = dependency('bilge-0.2-rs')
-bilge_impl_dep = dependency('bilge-impl-0.2-rs')
-
 _libpl011_rs = static_library(
   'pl011',
   files('src/lib.rs'),
   override_options: ['rust_std=2021', 'build.rust_std=2021'],
   rust_abi: 'rust',
   dependencies: [
-    bilge_dep,
+    bilge_rs,
-    bilge_impl_dep,
+    bilge_impl_rs,
     qemu_api,
     qemu_api_macros,
   ],
@@ -21,6 +15,6 @@ rust_devices_ss.add(when: 'CONFIG_X_PL011_RUST', if_true: [declare_dependency(
   link_whole: [_libpl011_rs],
   # Putting proc macro crates in `dependencies` is necessary for Meson to find
   # them when compiling the root per-target static rust lib.
-  dependencies: [bilge_impl_dep, qemu_api_macros],
+  dependencies: [bilge_impl_rs, qemu_api_macros],
   variables: {'crate': 'pl011'},
 )])

rust/meson.build

@@ -1,3 +1,19 @@
+subproject('bilge-0.2-rs', required: true)
+subproject('bilge-impl-0.2-rs', required: true)
+subproject('libc-0.2-rs', required: true)
+
+bilge_rs = dependency('bilge-0.2-rs')
+bilge_impl_rs = dependency('bilge-impl-0.2-rs')
+libc_rs = dependency('libc-0.2-rs')
+
+subproject('proc-macro2-1-rs', required: true)
+subproject('quote-1-rs', required: true)
+subproject('syn-2-rs', required: true)
+
+quote_rs_native = dependency('quote-1-rs', native: true)
+syn_rs_native = dependency('syn-2-rs', native: true)
+proc_macro2_rs_native = dependency('proc-macro2-1-rs', native: true)
+
 subdir('qemu-api-macros')
 subdir('qemu-api')
 

rust/qemu-api-macros/meson.build

@@ -1,11 +1,3 @@
-subproject('proc-macro2-1-rs', required: true)
-subproject('quote-1-rs', required: true)
-subproject('syn-2-rs', required: true)
-
-quote_dep = dependency('quote-1-rs', native: true)
-syn_dep = dependency('syn-2-rs', native: true)
-proc_macro2_dep = dependency('proc-macro2-1-rs', native: true)
-
 _qemu_api_macros_rs = rust.proc_macro(
   'qemu_api_macros',
   files('src/lib.rs'),
@@ -16,9 +8,9 @@ _qemu_api_macros_rs = rust.proc_macro(
     '--cfg', 'feature="proc-macro"',
   ],
   dependencies: [
-    proc_macro2_dep,
+    proc_macro2_rs_native,
-    quote_dep,
+    quote_rs_native,
-    syn_dep,
+    syn_rs_native,
   ],
 )
 

rust/qemu-api/meson.build

@@ -2,8 +2,6 @@ _qemu_api_cfg = run_command(rustc_args,
   '--config-headers', config_host_h, '--features', files('Cargo.toml'),
   capture: true, check: true).stdout().strip().splitlines()
 
-libc_dep = dependency('libc-0.2-rs')
-
 # _qemu_api_cfg += ['--cfg', 'feature="allocator"']
 if get_option('debug_mutex')
   _qemu_api_cfg += ['--cfg', 'feature="debug_cell"']
@@ -37,7 +35,7 @@ _qemu_api_rs = static_library(
   override_options: ['rust_std=2021', 'build.rust_std=2021'],
   rust_abi: 'rust',
   rust_args: _qemu_api_cfg,
-  dependencies: [libc_dep, qemu_api_macros],
+  dependencies: [libc_rs, qemu_api_macros],
 )
 
 rust.test('rust-qemu-api-tests', _qemu_api_rs,