blob: 716e02cd5aad223e174ae7f57e5ace6c6487b9b7 [file] [log] [blame]
""" 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
GraphNodeInfo = provider(
fields = {
"children": "Other GraphNodeInfo from dependencies of this target",
"label": "Label of the target visited",
"linked_statically_by": "The value of this attribute if the target has it",
},
)
CcSharedLibraryInfo = provider(
fields = {
"dynamic_deps": "All shared libraries depended on transitively",
"linker_input": "the resulting linker input artifact for the shared library",
"exports": "cc_libraries that are linked statically and exported",
},
)
def _separate_static_and_dynamic_link_libraries(direct_children, can_be_linked_dynamically):
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)
if node.label in can_be_linked_dynamically:
link_dynamically_labels[node.label] = None
else:
link_statically_labels[node.label] = node.linked_statically_by
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 = []
linker_inputs.extend(dynamic_linker_inputs)
linker_inputs.extend(static_linker_inputs)
return cc_common.create_linking_context(
linker_inputs = depset(linker_inputs),
)
def _merge_cc_shared_library_infos(ctx):
dynamic_deps = []
transitive_dynamic_deps = []
for dep in ctx.attr.dynamic_deps:
dynamic_dep_entry = (
dep[CcSharedLibraryInfo].exports,
dep[CcSharedLibraryInfo].linker_input,
)
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:
str_export_label = str(export.label)
if str_export_label in exports_map:
fail("Two shared libraries in dependencies export the same symbols. Both " +
exports_map[str_export_label].libraries[0].dynamic_library.short_path +
" and " + linker_input.dynamic_library.short_path +
" export " + str_export_label)
exports_map[str(export.label)] = linker_input
return exports_map
def _filter_inputs(ctx, transitive_exports):
static_linker_inputs = []
dynamic_linker_inputs = []
graph_structure_aspect_nodes = []
linker_inputs = []
for export in ctx.attr.exports:
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:
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,
)
already_linked_dynamically = {}
for linker_input in linker_inputs:
owner = str(linker_input.owner)
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)
elif owner in link_statically_labels:
can_be_linked_statically = False
for linked_statically_by in link_statically_labels[owner]:
if linked_statically_by == str(ctx.label):
can_be_linked_statically = True
static_linker_inputs.append(linker_input)
break
if not can_be_linked_statically:
fail("We can't link " +
str(owner) + " either statically or dynamically")
else:
fail("Implementation error, this should not happen")
# 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 str(export.label) 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)
def _cc_shared_library_impl(ctx):
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))
(static_linker_inputs, dynamic_linker_inputs) = _filter_inputs(ctx, exports_map)
linking_context = _create_linker_context(ctx, static_linker_inputs, dynamic_linker_inputs)
user_link_flags = []
additional_inputs = []
if ctx.file.visibility_file != None:
user_link_flags = [
"-Wl,--no-undefined", # Just here for testing.
"-Wl,--version-script=" + ctx.file.visibility_file.path,
]
additional_inputs = [ctx.file.visibility_file]
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 = additional_inputs,
name = ctx.label.name,
output_type = "dynamic_library",
)
return [
DefaultInfo(files = depset([linking_outputs.library_to_link.resolved_symlink_dynamic_library])),
CcSharedLibraryInfo(
dynamic_deps = merged_cc_shared_library_info,
exports = ctx.attr.exports,
linker_input = cc_common.create_linker_input(owner = ctx.label, libraries = depset([linking_outputs.library_to_link])),
),
]
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])
linked_statically_by = []
if hasattr(ctx.rule.attr, "linked_statically_by"):
linked_statically_by = ctx.rule.attr.linked_statically_by
return [GraphNodeInfo(
label = str(ctx.label),
linked_statically_by = linked_statically_by,
children = children,
)]
graph_structure_aspect = aspect(
attr_aspects = ["*"],
implementation = _graph_structure_aspect_impl,
)
cc_shared_library = rule(
implementation = _cc_shared_library_impl,
attrs = {
"dynamic_deps": attr.label_list(providers = [CcSharedLibraryInfo]),
"visibility_file": attr.label(allow_single_file = True),
"exports": attr.label_list(aspects = [graph_structure_aspect]),
"_cc_toolchain": attr.label(default = "@bazel_tools//tools/cpp:current_cc_toolchain"),
},
toolchains = ["//cc:toolchain_type"],
fragments = ["cpp"],
)