C++: Fixes order for cc_shared_library linked libs

Before dynamic lib dependencies of cc_shared_library were always linked at the
end. Now for creating the command line we respect the topological order that
would be given when getting the libs from the dependency graph created by the
cc_libraries.

RELNOTES:none
PiperOrigin-RevId: 295676824
Change-Id: I327a0e10920f18fed234dd5835e54cab75a0d428

examples/experimental_cc_shared_library.bzl

@@ -51,13 +51,7 @@ def _separate_static_and_dynamic_link_libraries(
             all_children.extend(node.children)
     return (link_statically_labels, link_dynamically_labels)
 
-def _create_linker_context(ctx, static_linker_inputs, dynamic_linker_inputs):
-    linker_inputs = []
-
-    # Statically linked symbols should take precedence over dynamically linked.
-    linker_inputs.extend(static_linker_inputs)
-    linker_inputs.extend(dynamic_linker_inputs)
-
+def _create_linker_context(ctx, linker_inputs):
     return cc_common.create_linking_context(
         linker_inputs = depset(linker_inputs, order = "topological"),
     )
@@ -154,19 +148,19 @@ def _filter_inputs(
         transitive_exports,
         preloaded_deps_direct_labels,
         static_libs_map):
-    static_linker_inputs = []
-    dynamic_linker_inputs = []
+    linker_inputs = []
+    static_libs = []
 
     graph_structure_aspect_nodes = []
-    linker_inputs = []
+    dependency_linker_inputs = []
     direct_exports = {}
     for export in ctx.attr.exports:
         direct_exports[str(export.label)] = True
-        linker_inputs.extend(export[CcInfo].linking_context.linker_inputs.to_list())
+        dependency_linker_inputs.extend(export[CcInfo].linking_context.linker_inputs.to_list())
         graph_structure_aspect_nodes.append(export[GraphNodeInfo])
 
     can_be_linked_dynamically = {}
-    for linker_input in linker_inputs:
+    for linker_input in dependency_linker_inputs:
         owner = str(linker_input.owner)
         if owner in transitive_exports:
             can_be_linked_dynamically[owner] = True
@@ -177,30 +171,30 @@ def _filter_inputs(
         preloaded_deps_direct_labels,
     )
 
-    already_linked_dynamically = {}
     owners_seen = {}
-    for linker_input in linker_inputs:
+    for linker_input in dependency_linker_inputs:
         owner = str(linker_input.owner)
         if owner in owners_seen:
             continue
         owners_seen[owner] = True
         if owner in link_dynamically_labels:
             dynamic_linker_input = transitive_exports[owner]
-            if str(dynamic_linker_input.owner) not in already_linked_dynamically:
-                already_linked_dynamically[str(dynamic_linker_input.owner)] = True
-                dynamic_linker_inputs.append(dynamic_linker_input)
+            linker_inputs.append(dynamic_linker_input)
         elif owner in link_statically_labels:
             if owner in static_libs_map:
                 fail(owner + " is already linked statically in " +
                      static_libs_map[owner] + " but not exported")
 
             if owner in direct_exports:
-                static_linker_inputs.append(_wrap_static_library_with_alwayslink(
+                wrapped_library = _wrap_static_library_with_alwayslink(
                     ctx,
                     feature_configuration,
                     cc_toolchain,
                     linker_input,
-                ))
+                )
+
+                static_libs.append(owner)
+                linker_inputs.append(wrapped_library)
             else:
                 can_be_linked_statically = False
 
@@ -212,25 +206,13 @@ def _filter_inputs(
                         can_be_linked_statically = True
                         break
                 if can_be_linked_statically:
-                    static_linker_inputs.append(linker_input)
+                    static_libs.append(owner)
+                    linker_inputs.append(linker_input)
                 else:
                     fail("We can't link " +
                          str(owner) + " either statically or dynamically")
 
-    # Every direct dynamic_dep of this rule will be linked dynamically even if we
-    # didn't reach a cc_library exported by one of these dynamic_deps. In other
-    # words, the shared library might link more shared libraries than we need
-    # in the cc_library graph.
-    for dep in ctx.attr.dynamic_deps:
-        has_a_used_export = False
-        for export in dep[CcSharedLibraryInfo].exports:
-            if export in link_dynamically_labels:
-                has_a_used_export = True
-                break
-        if not has_a_used_export:
-            dynamic_linker_inputs.append(dep[CcSharedLibraryInfo].linker_input)
-
-    return (static_linker_inputs, dynamic_linker_inputs)
+    return (linker_inputs, static_libs)
 
 def _same_package_or_above(label_a, label_b):
     if label_a.workspace_name != label_b.workspace_name:
@@ -285,7 +267,8 @@ def _cc_shared_library_impl(ctx):
         preloaded_dep_merged_cc_info = cc_common.merge_cc_infos(cc_infos = preloaded_deps_cc_infos)
 
     static_libs_map = _build_static_libs_map(merged_cc_shared_library_info)
-    (static_linker_inputs, dynamic_linker_inputs) = _filter_inputs(
+
+    (linker_inputs, static_libs) = _filter_inputs(
         ctx,
         feature_configuration,
         cc_toolchain,
@@ -294,7 +277,7 @@ def _cc_shared_library_impl(ctx):
         static_libs_map,
     )
 
-    linking_context = _create_linker_context(ctx, static_linker_inputs, dynamic_linker_inputs)
+    linking_context = _create_linker_context(ctx, linker_inputs)
 
     # TODO(plf): Decide whether ctx.attr.user_link_flags should come before or after options
     # added by the rule logic.
@@ -329,10 +312,6 @@ def _cc_shared_library_impl(ctx):
     for export in ctx.attr.exports:
         exports.append(str(export.label))
 
-    static_libs = []
-    for static_linker_input in static_linker_inputs:
-        static_libs.append(str(static_linker_input.owner))
-
     return [
         DefaultInfo(
             files = depset([linking_outputs.library_to_link.resolved_symlink_dynamic_library]),

examples/test_cc_shared_library/BUILD

@@ -1,5 +1,6 @@
 load("//cc:defs.bzl", "cc_binary", "cc_library", "cc_test")
 load("//examples:experimental_cc_shared_library.bzl", "cc_shared_library")
+load(":starlark_tests.bzl", "linking_suffix_test")
 
 cc_test(
     name = "cc_test",
@@ -135,3 +136,8 @@ sh_test(
         ":foo_so",
     ],
 )
+
+linking_suffix_test(
+    name = "linking_action_test",
+    target_under_test = ":foo_so",
+)

examples/test_cc_shared_library/starlark_tests.bzl

@@ -0,0 +1,18 @@
+"""Starlark tests for cc_shared_library"""
+
+load("@bazel_skylib//lib:unittest.bzl", "analysistest", "asserts")
+
+def _linking_suffix_test_impl(ctx):
+    env = analysistest.begin(ctx)
+
+    target_under_test = analysistest.target_under_test(env)
+    actions = analysistest.target_actions(env)
+
+    for arg in reversed(actions[1].argv):
+        if arg.find(".a") != -1 or arg.find("-l") != -1:
+            asserts.equals(env, "libbar4.a", arg[arg.rindex("/") + 1:])
+            break
+
+    return analysistest.end(env)
+
+linking_suffix_test = analysistest.make(_linking_suffix_test_impl)