"""This is an experimental implementation of cc_shared_library. We may change the implementation at any moment or even delete this file. Do not rely on this. It requires bazel >1.2 and passing the flag --experimental_cc_shared_library """ load("//cc:find_cc_toolchain.bzl", "find_cc_toolchain") # TODO(#5200): Add export_define to library_to_link and cc_library # Add this as a tag to any target that can be linked by more than one # cc_shared_library because it doesn't have static initializers or anything # else that may cause issues when being linked more than once. This should be # used sparingly after making sure it's safe to use. LINKABLE_MORE_THAN_ONCE = "LINKABLE_MORE_THAN_ONCE" _EXPORTED_BY_TAG_BEGINNING = "exported_by=" def exported_by(labels): str_builder = [] for label in labels: str_builder.append(label) return _EXPORTED_BY_TAG_BEGINNING + ",".join(str_builder) GraphNodeInfo = provider( fields = { "children": "Other GraphNodeInfo from dependencies of this target", "exported_by": "Labels of targets that can export the library of this node", "label": "Label of the target visited", "linkable_more_than_once": "Linkable into more than a single cc_shared_library", }, ) CcSharedLibraryInfo = provider( fields = { "dynamic_deps": "All shared libraries depended on transitively", "exports": "cc_libraries that are linked statically and exported", "link_once_static_libs": "All libraries linked statically into this library that should " + "only be linked once, e.g. because they have static " + "initializers. If we try to link them more than once, " + "we will throw an error", "linker_input": "the resulting linker input artifact for the shared library", "preloaded_deps": "cc_libraries needed by this cc_shared_library that should" + " be linked the binary. If this is set, this cc_shared_library has to " + " be a direct dependency of the cc_binary", }, ) def _separate_static_and_dynamic_link_libraries( direct_children, can_be_linked_dynamically, preloaded_deps_direct_labels): node = None all_children = list(direct_children) link_statically_labels = {} link_dynamically_labels = {} # Horrible I know. Perhaps Starlark team gives me a way to prune a tree. for i in range(1, 2147483647): if len(all_children) == 0: break node = all_children.pop(0) node_label = str(node.label) if node_label in can_be_linked_dynamically: link_dynamically_labels[node_label] = True elif node_label not in preloaded_deps_direct_labels: link_statically_labels[node_label] = node.linkable_more_than_once all_children.extend(node.children) return (link_statically_labels, link_dynamically_labels) def _create_linker_context(ctx, linker_inputs): return cc_common.create_linking_context( linker_inputs = depset(linker_inputs, order = "topological"), ) def _merge_cc_shared_library_infos(ctx): dynamic_deps = [] transitive_dynamic_deps = [] for dep in ctx.attr.dynamic_deps: if dep[CcSharedLibraryInfo].preloaded_deps != None: fail("{} can only be a direct dependency of a " + " cc_binary because it has " + "preloaded_deps".format(str(dep.label))) dynamic_dep_entry = ( dep[CcSharedLibraryInfo].exports, dep[CcSharedLibraryInfo].linker_input, dep[CcSharedLibraryInfo].link_once_static_libs, ) dynamic_deps.append(dynamic_dep_entry) transitive_dynamic_deps.append(dep[CcSharedLibraryInfo].dynamic_deps) return depset(direct = dynamic_deps, transitive = transitive_dynamic_deps) def _build_exports_map_from_only_dynamic_deps(merged_shared_library_infos): exports_map = {} for entry in merged_shared_library_infos.to_list(): exports = entry[0] linker_input = entry[1] for export in exports: if export in exports_map: fail("Two shared libraries in dependencies export the same symbols. Both " + exports_map[export].libraries[0].dynamic_library.short_path + " and " + linker_input.dynamic_library.short_path + " export " + export) exports_map[export] = linker_input return exports_map def _build_link_once_static_libs_map(merged_shared_library_infos): link_once_static_libs_map = {} for entry in merged_shared_library_infos.to_list(): link_once_static_libs = entry[2] linker_input = entry[1] for static_lib in link_once_static_libs: if static_lib in link_once_static_libs_map: fail("Two shared libraries in dependencies link the same " + " library statically. Both " + link_once_static_libs_map[static_lib] + " and " + str(linker_input.owner) + " link statically" + static_lib) link_once_static_libs_map[static_lib] = str(linker_input.owner) return link_once_static_libs_map def _wrap_static_library_with_alwayslink(ctx, feature_configuration, cc_toolchain, linker_input): new_libraries_to_link = [] for old_library_to_link in linker_input.libraries: # TODO(#5200): This will lose the object files from a library to link. # Not too bad for the prototype but as soon as the library_to_link # constructor has object parameters this should be changed. new_library_to_link = cc_common.create_library_to_link( actions = ctx.actions, feature_configuration = feature_configuration, cc_toolchain = cc_toolchain, static_library = old_library_to_link.static_library, pic_static_library = old_library_to_link.pic_static_library, alwayslink = True, ) new_libraries_to_link.append(new_library_to_link) return cc_common.create_linker_input( owner = linker_input.owner, libraries = depset(direct = new_libraries_to_link), user_link_flags = depset(direct = linker_input.user_link_flags), additional_inputs = depset(direct = linker_input.additional_inputs), ) def _check_if_target_under_path(value, pattern): if pattern.workspace_name != value.workspace_name: return False if pattern.name == "__pkg__": return pattern.package == value.package if pattern.name == "__subpackages__": return _same_package_or_above(pattern, value) return pattern.package == value.package and pattern.name == value.name def _filter_inputs( ctx, feature_configuration, cc_toolchain, transitive_exports, preloaded_deps_direct_labels, link_once_static_libs_map): linker_inputs = [] link_once_static_libs = [] graph_structure_aspect_nodes = [] dependency_linker_inputs = [] direct_exports = {} for export in ctx.attr.exports: direct_exports[str(export.label)] = True 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 dependency_linker_inputs: owner = str(linker_input.owner) if owner in transitive_exports: can_be_linked_dynamically[owner] = True (link_statically_labels, link_dynamically_labels) = _separate_static_and_dynamic_link_libraries( graph_structure_aspect_nodes, can_be_linked_dynamically, preloaded_deps_direct_labels, ) owners_seen = {} 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] linker_inputs.append(dynamic_linker_input) elif owner in link_statically_labels: if owner in link_once_static_libs_map: fail(owner + " is already linked statically in " + link_once_static_libs_map[owner] + " but not exported") if owner in direct_exports: wrapped_library = _wrap_static_library_with_alwayslink( ctx, feature_configuration, cc_toolchain, linker_input, ) if not link_statically_labels[owner]: link_once_static_libs.append(owner) linker_inputs.append(wrapped_library) else: can_be_linked_statically = False for static_dep_path in ctx.attr.static_deps: static_dep_path_label = ctx.label.relative(static_dep_path) owner_label = linker_input.owner if _check_if_target_under_path(linker_input.owner, static_dep_path_label): can_be_linked_statically = True break if can_be_linked_statically: if not link_statically_labels[owner]: link_once_static_libs.append(owner) linker_inputs.append(linker_input) else: fail("We can't link " + str(owner) + " either statically or dynamically") return (linker_inputs, link_once_static_libs) def _same_package_or_above(label_a, label_b): if label_a.workspace_name != label_b.workspace_name: return False package_a_tokenized = label_a.package.split("/") package_b_tokenized = label_b.package.split("/") if len(package_b_tokenized) < len(package_a_tokenized): return False for i in range(len(package_a_tokenized)): if package_a_tokenized[i] != package_b_tokenized[i]: return False return True def _cc_shared_library_impl(ctx): cc_common.check_experimental_cc_shared_library() cc_toolchain = find_cc_toolchain(ctx) feature_configuration = cc_common.configure_features( ctx = ctx, cc_toolchain = cc_toolchain, requested_features = ctx.features, unsupported_features = ctx.disabled_features, ) merged_cc_shared_library_info = _merge_cc_shared_library_infos(ctx) exports_map = _build_exports_map_from_only_dynamic_deps(merged_cc_shared_library_info) for export in ctx.attr.exports: if str(export.label) in exports_map: fail("Trying to export a library already exported by a different shared library: " + str(export.label)) can_be_exported = _same_package_or_above(ctx.label, export.label) if not can_be_exported: for exported_by in export[GraphNodeInfo].exported_by: exported_by_label = Label(exported_by) if _check_if_target_under_path(ctx.label, exported_by_label): can_be_exported = True break if not can_be_exported: fail(str(export.label) + " cannot be exported from " + str(ctx.label) + " because it's not in the same package/subpackage or the library " + "to be exported doesn't have this cc_shared_library in the exported_by tag.") preloaded_deps_direct_labels = {} preloaded_dep_merged_cc_info = None if len(ctx.attr.preloaded_deps) != 0: preloaded_deps_cc_infos = [] for preloaded_dep in ctx.attr.preloaded_deps: preloaded_deps_direct_labels[str(preloaded_dep.label)] = True preloaded_deps_cc_infos.append(preloaded_dep[CcInfo]) preloaded_dep_merged_cc_info = cc_common.merge_cc_infos(cc_infos = preloaded_deps_cc_infos) link_once_static_libs_map = _build_link_once_static_libs_map(merged_cc_shared_library_info) (linker_inputs, link_once_static_libs) = _filter_inputs( ctx, feature_configuration, cc_toolchain, exports_map, preloaded_deps_direct_labels, link_once_static_libs_map, ) linking_context = _create_linker_context(ctx, linker_inputs) user_link_flags = [] for user_link_flag in ctx.attr.user_link_flags: user_link_flags.append(ctx.expand_location(user_link_flag, targets = ctx.attr.additional_linker_inputs)) linking_outputs = cc_common.link( actions = ctx.actions, feature_configuration = feature_configuration, cc_toolchain = cc_toolchain, linking_contexts = [linking_context], user_link_flags = user_link_flags, additional_inputs = ctx.files.additional_linker_inputs, name = ctx.label.name, output_type = "dynamic_library", ) runfiles = ctx.runfiles( files = [linking_outputs.library_to_link.resolved_symlink_dynamic_library], ) for dep in ctx.attr.dynamic_deps: runfiles = runfiles.merge(dep[DefaultInfo].data_runfiles) exports = [] for export in ctx.attr.exports: exports.append(str(export.label)) return [ DefaultInfo( files = depset([linking_outputs.library_to_link.resolved_symlink_dynamic_library]), runfiles = runfiles, ), CcSharedLibraryInfo( dynamic_deps = merged_cc_shared_library_info, exports = exports, link_once_static_libs = link_once_static_libs, linker_input = cc_common.create_linker_input( owner = ctx.label, libraries = depset([linking_outputs.library_to_link]), ), preloaded_deps = preloaded_dep_merged_cc_info, ), ] def _graph_structure_aspect_impl(target, ctx): children = [] if hasattr(ctx.rule.attr, "deps"): for dep in ctx.rule.attr.deps: if GraphNodeInfo in dep: children.append(dep[GraphNodeInfo]) exported_by = [] linkable_more_than_once = False if hasattr(ctx.rule.attr, "tags"): for tag in ctx.rule.attr.tags: if tag.startswith(_EXPORTED_BY_TAG_BEGINNING) and len(tag) > len(_EXPORTED_BY_TAG_BEGINNING): for target in tag[len(_EXPORTED_BY_TAG_BEGINNING):].split(","): # Only absolute labels allowed. Targets in same package # or subpackage can be exported anyway. if not target.startswith("//") and not target.startswith("@"): fail("Labels in exported_by of " + str(target) + " must be absolute.") Label(target) # Checking synthax is ok. exported_by.append(target) elif tag == LINKABLE_MORE_THAN_ONCE: linkable_more_than_once = True return [GraphNodeInfo( label = ctx.label, children = children, exported_by = exported_by, linkable_more_than_once = linkable_more_than_once, )] graph_structure_aspect = aspect( attr_aspects = ["*"], implementation = _graph_structure_aspect_impl, ) cc_shared_library = rule( implementation = _cc_shared_library_impl, attrs = { "additional_linker_inputs": attr.label_list(allow_files = True), "dynamic_deps": attr.label_list(providers = [CcSharedLibraryInfo]), "exports": attr.label_list(providers = [CcInfo], aspects = [graph_structure_aspect]), "preloaded_deps": attr.label_list(providers = [CcInfo]), "static_deps": attr.string_list(), "user_link_flags": attr.string_list(), "_cc_toolchain": attr.label(default = "@bazel_tools//tools/cpp:current_cc_toolchain"), }, toolchains = ["@rules_cc//cc:toolchain_type"], # copybara-use-repo-external-label fragments = ["cpp"], ) for_testing_dont_use_check_if_target_under_path = _check_if_target_under_path