Add support for self-contained object files (musl). (#829)

rust/private/providers.bzl

@@ -59,6 +59,7 @@ StdLibInfo = provider(
         "between_core_and_std_files": "List[File]: `.a` files related to all modules except `adler`, `alloc`, `compiler_builtins`, `core`, and `std`.",
         "core_files": "List[File]: `.a` files related to the `core` and `adler` modules",
         "dot_a_files": "Depset[File]: Generated `.a` files",
+        "self_contained_files": "List[File]: All `.o` files from the `self-contained` directory.",
         "srcs": "List[Target]: The original `src` attribute.",
         "std_files": "Depset[File]: `.a` files associated with the `std` module.",
         "std_rlibs": "List[File]: All `.rlib` files",

rust/private/repository_utils.bzl

@@ -147,6 +147,7 @@ rust_stdlib_filegroup(
             "lib/rustlib/{target_triple}/lib/*.rlib",
             "lib/rustlib/{target_triple}/lib/*{dylib_ext}",
             "lib/rustlib/{target_triple}/lib/*{staticlib_ext}",
+            "lib/rustlib/{target_triple}/lib/self-contained/**",
         ],
         # Some patterns (e.g. `lib/*.a`) don't match anything, see https://github.com/bazelbuild/rules_rust/pull/245
         allow_empty = True,

rust/toolchain.bzl

@@ -11,6 +11,11 @@ def _rust_stdlib_filegroup_impl(ctx):
     between_core_and_std_files = []
     std_files = []
     alloc_files = []
+    self_contained_files = [
+        file
+        for file in rust_lib
+        if file.basename.endswith(".o") and "self-contained" in file.path
+    ]
 
     std_rlibs = [f for f in rust_lib if f.basename.endswith(".rlib")]
     if std_rlibs:
@@ -53,6 +58,7 @@ def _rust_stdlib_filegroup_impl(ctx):
             between_core_and_std_files = between_core_and_std_files,
             std_files = std_files,
             alloc_files = alloc_files,
+            self_contained_files = self_contained_files,
         ),
     ]
 
@@ -101,7 +107,7 @@ def _make_libstd_and_allocator_ccinfo(ctx, rust_lib, allocator_library):
         A CcInfo object for the required libraries, or None if no such libraries are available.
     """
     cc_toolchain, feature_configuration = find_cc_toolchain(ctx)
-    link_inputs = []
+    cc_infos = []
 
     if not rust_common.stdlib_info in ctx.attr.rust_lib:
         fail(dedent("""\
@@ -112,6 +118,23 @@ def _make_libstd_and_allocator_ccinfo(ctx, rust_lib, allocator_library):
         """).format(ctx.label, ctx.attr.rust_lib))
     rust_stdlib_info = ctx.attr.rust_lib[rust_common.stdlib_info]
 
+    if rust_stdlib_info.self_contained_files:
+        compilation_outputs = cc_common.create_compilation_outputs(
+            objects = depset(rust_stdlib_info.self_contained_files),
+        )
+
+        linking_context, _linking_outputs = cc_common.create_linking_context_from_compilation_outputs(
+            name = ctx.label.name,
+            actions = ctx.actions,
+            feature_configuration = feature_configuration,
+            cc_toolchain = cc_toolchain,
+            compilation_outputs = compilation_outputs,
+        )
+
+        cc_infos.append(CcInfo(
+            linking_context = linking_context,
+        ))
+
     if rust_stdlib_info.std_rlibs:
         alloc_inputs = depset(
             [_ltl(f, ctx, cc_toolchain, feature_configuration) for f in rust_stdlib_info.alloc_files],
@@ -160,22 +183,29 @@ def _make_libstd_and_allocator_ccinfo(ctx, rust_lib, allocator_library):
             order = "topological",
         )
 
-        link_inputs.append(cc_common.create_linker_input(
+        link_inputs = cc_common.create_linker_input(
             owner = rust_lib.label,
             libraries = std_inputs,
-        ))
+        )
 
-    allocator_inputs = None
-    if allocator_library:
-        allocator_inputs = [allocator_library[CcInfo].linking_context.linker_inputs]
+        allocator_inputs = None
+        if allocator_library:
+            allocator_inputs = [allocator_library[CcInfo].linking_context.linker_inputs]
+
+        cc_infos.append(CcInfo(
+            linking_context = cc_common.create_linking_context(
+                linker_inputs = depset(
+                    [link_inputs],
+                    transitive = allocator_inputs,
+                    order = "topological",
+                ),
+            ),
+        ))
 
-    libstd_and_allocator_ccinfo = None
-    if link_inputs:
-        return CcInfo(linking_context = cc_common.create_linking_context(linker_inputs = depset(
-            link_inputs,
-            transitive = allocator_inputs,
-            order = "topological",
-        )))
+    if cc_infos:
+        return cc_common.merge_cc_infos(
+            direct_cc_infos = cc_infos,
+        )
     return None
 
 def _rust_toolchain_impl(ctx):