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Support linking on Windows with rules-based toolchains #436

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19980f5
Support linking on Windows
calebzulawski Jul 9, 2025
07626f6
Add Windows golden textproto
calebzulawski Jul 9, 2025
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13 changes: 0 additions & 13 deletions cc/toolchains/args/BUILD
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Original file line number Diff line number Diff line change
@@ -1,4 +1,3 @@
load("//cc/toolchains:feature.bzl", "cc_feature")
load("//cc/toolchains:feature_set.bzl", "cc_feature_set")

package(default_visibility = ["//visibility:public"])
Expand All @@ -15,7 +14,6 @@ package(default_visibility = ["//visibility:public"])
cc_feature_set(
name = "experimental_replace_legacy_action_config_features",
all_of = [
":backfill_legacy_args",
"//cc/toolchains/args/archiver_flags:feature",
"//cc/toolchains/args/pic_flags:feature",
"//cc/toolchains/args/libraries_to_link:feature",
Expand All @@ -40,14 +38,3 @@ cc_feature_set(
"//cc/toolchains/args/compile_flags:feature", # NOTE: This should come below default flags so user flags can override them
],
)

cc_feature(
name = "backfill_legacy_args",
feature_name = "experimental_replace_legacy_action_config_features",
# TODO: Convert remaining items in this list into their actual args.
implies = [
"//cc/toolchains/features/legacy:build_interface_libraries",
"//cc/toolchains/features/legacy:dynamic_library_linker_tool",
],
visibility = ["//visibility:private"],
)
6 changes: 5 additions & 1 deletion cc/toolchains/args/libraries_to_link/BUILD
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Expand Up @@ -77,6 +77,7 @@ cc_nested_args(
name = "single_library_args",
nested = select({
"@platforms//os:macos": [],
"@platforms//os:windows": [],
"//conditions:default": [":optional_whole_archive_start"],
}) + [
":optional_object_file_group",
Expand All @@ -85,11 +86,14 @@ cc_nested_args(
":optional_static_library",
":optional_dynamic_library",
] + select({
# maOS has a minor nuance where it uses the path to the library instead of `-l:{library_name}`.
# macOS has a minor nuance where it uses the path to the library instead of `-l:{library_name}`.
"@platforms//os:macos": [":macos_optional_versioned_dynamic_library"],
# Windows references the interface library (if.lib) rather than the dynamic library (dll)
"@platforms//os:windows": [],
"//conditions:default": [":generic_optional_versioned_dynamic_library"],
}) + select({
"@platforms//os:macos": [],
"@platforms//os:windows": [],
"//conditions:default": [":optional_whole_archive_end"],
}),
)
Expand Down
46 changes: 46 additions & 0 deletions cc/toolchains/args/libraries_to_link/private/library_link_args.bzl
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Expand Up @@ -49,6 +49,40 @@ def macos_force_load_library_args(name, variable):
},
)

def windows_whole_archive_args(name, variable):
"""A helper for declaring /WHOLEARCHIVE argument expansion for a library.

This creates an argument expansion that will expand to /WHOLEARCHIVE:<library>
if the library should be linked as a whole archive.

Args:
name: The name of the rule.
variable: The variable to expand.
"""
cc_nested_args(
name = name,
nested = [
":{}_whole_archive".format(name),
":{}_no_whole_archive".format(name),
],
)
cc_nested_args(
name = name + "_no_whole_archive",
requires_false = "//cc/toolchains/variables:libraries_to_link.is_whole_archive",
args = ["{library}"],
format = {
"library": variable,
},
)
cc_nested_args(
name = name + "_whole_archive",
requires_true = "//cc/toolchains/variables:libraries_to_link.is_whole_archive",
args = ["-Wl,/WHOLEARCHIVE:{library}"],
format = {
"library": variable,
},
)

def library_link_args(name, library_type, from_variable, iterate_over_variable = False):
"""A helper for declaring a library to link.

Expand Down Expand Up @@ -78,6 +112,7 @@ def library_link_args(name, library_type, from_variable, iterate_over_variable =
name = name,
actual = select({
"@platforms//os:macos": ":macos_{}".format(name),
"@platforms//os:windows": ":windows_{}".format(name),
"//conditions:default": ":generic_{}".format(name),
}),
)
Expand All @@ -102,3 +137,14 @@ def library_link_args(name, library_type, from_variable, iterate_over_variable =
name = "{}_maybe_force_load".format(name),
variable = from_variable,
)
cc_nested_args(
name = "windows_{}".format(name),
requires_equal = "//cc/toolchains/variables:libraries_to_link.type",
requires_equal_value = library_type,
iterate_over = from_variable if iterate_over_variable else None,
nested = [":{}_maybe_whole_archive".format(name)],
)
windows_whole_archive_args(
name = "{}_maybe_whole_archive".format(name),
variable = from_variable,
)
93 changes: 93 additions & 0 deletions cc/toolchains/args/link_flags/BUILD
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@@ -1,13 +1,16 @@
load("//cc/toolchains:args.bzl", "cc_args")
load("//cc/toolchains:feature.bzl", "cc_feature")
load("//cc/toolchains:feature_set.bzl", "cc_feature_set")
load("//cc/toolchains:nested_args.bzl", "cc_nested_args")

cc_feature_set(
name = "feature",
all_of = [
":user_link_flags_feature",
":legacy_link_flags_feature",
":output_link_flags_feature",
":build_interface_libraries_feature",
":dynamic_library_linker_tool_feature",
],
visibility = ["//visibility:public"],
)
Expand Down Expand Up @@ -58,3 +61,93 @@ cc_args(
format = {"output_execpath": "//cc/toolchains/variables:output_execpath"},
requires_not_none = "//cc/toolchains/variables:output_execpath",
)

cc_feature(
name = "build_interface_libraries_feature",
args = ["build_interface_libraries"],
overrides = "//cc/toolchains/features/legacy:build_interface_libraries",
)

cc_args(
name = "build_interface_libraries",
actions = ["//cc/toolchains/actions:dynamic_library_link_actions"],
nested = [":build_interface_libraries_check"],
requires_not_none = "//cc/toolchains/variables:generate_interface_library",
)

cc_nested_args(
name = "build_interface_libraries_check",
nested = select({
"@platforms//os:windows": [":windows_build_interface_libraries"],
"//conditions:default": [":generic_build_interface_libraries"],
}),
requires_equal = "//cc/toolchains/variables:generate_interface_library",
requires_equal_value = "yes",
)

cc_nested_args(
name = "windows_build_interface_libraries",
args = ["-Wl,/IMPLIB:{interface_library_output_path}"],
format = {"interface_library_output_path": "//cc/toolchains/variables:interface_library_output_path"},
requires_not_none = "//cc/toolchains/variables:interface_library_output_path",
)

cc_nested_args(
name = "generic_build_interface_libraries",
nested = [
":generate_interface_library",
":interface_library_builder_path",
":interface_library_input_path",
":interface_library_output_path",
],
)
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I copied this from the legacy toolchain config, I don't know enough about how it works to be sure my implementation is correct:

rules_cc/cc/private/toolchain/unix_cc_toolchain_config.bzl

Lines 1119 to 1147 in 0692005

build_interface_libraries_feature = feature(
name = "build_interface_libraries",
flag_sets = [
flag_set(
actions = [
ACTION_NAMES.cpp_link_dynamic_library,
ACTION_NAMES.cpp_link_nodeps_dynamic_library,
ACTION_NAMES.lto_index_for_dynamic_library,
ACTION_NAMES.lto_index_for_nodeps_dynamic_library,
],
flag_groups = [
flag_group(
flags = [
"%{generate_interface_library}",
"%{interface_library_builder_path}",
"%{interface_library_input_path}",
"%{interface_library_output_path}",
],
expand_if_available = "generate_interface_library",
),
],
with_features = [
with_feature_set(
features = ["supports_interface_shared_libraries"],
),
],
),
],
)


cc_nested_args(
name = "generate_interface_library",
args = ["{generate_interface_library}"],
format = {"generate_interface_library": "//cc/toolchains/variables:generate_interface_library"},
)

cc_nested_args(
name = "interface_library_builder_path",
args = ["{interface_library_builder_path}"],
format = {"interface_library_builder_path": "//cc/toolchains/variables:interface_library_builder_path"},
requires_not_none = "//cc/toolchains/variables:interface_library_builder_path",
)

cc_nested_args(
name = "interface_library_input_path",
args = ["{interface_library_input_path}"],
format = {"interface_library_input_path": "//cc/toolchains/variables:interface_library_input_path"},
requires_not_none = "//cc/toolchains/variables:interface_library_input_path",
)

cc_nested_args(
name = "interface_library_output_path",
args = ["{interface_library_output_path}"],
format = {"interface_library_output_path": "//cc/toolchains/variables:interface_library_output_path"},
requires_not_none = "//cc/toolchains/variables:interface_library_output_path",
)

cc_feature(
name = "dynamic_library_linker_tool_feature",
args = select({
"@platforms//os:windows": [],
"//conditions:default": ["dynamic_library_linker_tool"],
}),
overrides = "//cc/toolchains/features/legacy:dynamic_library_linker_tool",
)

cc_args(
name = "dynamic_library_linker_tool",
actions = ["//cc/toolchains/actions:dynamic_library_link_actions"],
nested = [":dynamic_library_linker_tool_check"],
requires_not_none = "//cc/toolchains/variables:generate_interface_library",
)

cc_nested_args(
name = "dynamic_library_linker_tool_check",
args = [" + cppLinkDynamicLibraryToolPath + "],
requires_equal = "//cc/toolchains/variables:generate_interface_library",
requires_equal_value = "yes",
)
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I based this on the legacy toolchain config as well:

rules_cc/cc/private/toolchain/unix_cc_toolchain_config.bzl

Lines 1494 to 1517 in 0692005

dynamic_library_linker_tool_feature = feature(
name = "dynamic_library_linker_tool",
flag_sets = [
flag_set(
actions = [
ACTION_NAMES.cpp_link_dynamic_library,
ACTION_NAMES.cpp_link_nodeps_dynamic_library,
ACTION_NAMES.lto_index_for_dynamic_library,
ACTION_NAMES.lto_index_for_nodeps_dynamic_library,
],
flag_groups = [
flag_group(
flags = [" + cppLinkDynamicLibraryToolPath + "],
expand_if_available = "generate_interface_library",
),
],
with_features = [
with_feature_set(
features = ["supports_interface_shared_libraries"],
),
],
),
],
)

5 changes: 4 additions & 1 deletion cc/toolchains/args/runtime_library_search_directories/BUILD
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Expand Up @@ -8,7 +8,10 @@ package(default_visibility = ["//visibility:private"])

cc_feature(
name = "feature",
args = [":runtime_library_search_directories"],
args = select({
"@platforms//os:windows": [],
"//conditions:default": [":runtime_library_search_directories"],
}),
overrides = "//cc/toolchains/features/legacy:runtime_library_search_directories",
visibility = ["//visibility:public"],
)
Expand Down
5 changes: 4 additions & 1 deletion cc/toolchains/args/strip_debug_symbols/BUILD
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Expand Up @@ -12,6 +12,9 @@ cc_feature(
cc_args(
name = "strip_debug_symbols",
actions = ["//cc/toolchains/actions:link_actions"],
args = ["-Wl,-S"],
args = select({
"@platforms//os:windows": ["-Wl,/DEBUG:NONE"],
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Not totally sure how this should be handled because this will not work with normal clang.exe and gcc.exe (if youre compiling with mingw).

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I hinted at this in the PR description--the idea is to use a variable. Bazel can be modified to include the compiler variable from create_cc_toolchain_config_info. After that's available, the args can be conditioned on that with something like:

cc_args(
    name = "mingw_args",
    require_equal = "//toolchain/variables:compiler",
    require_equal_value = "mingw",
    args = LINUX_ARGS,
 )
 
 cc_args(
    name = "msvc_args",
    require_equal = "//toolchain/variables:compiler",
    require_equal_value = "msvc",
    args = MSVC_ARGS,
 )
 
 cc_args_list(
     name = "windows_args",
     args = ["mingw_args", "msvc_args"],
 )

I'd plan on implementing a macro to generally support this, since there would be so many instances of it.

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Unfortunately I'm not really sure how to make Bazel support that, but if someone else is willing to do that, I'd be happy to do the rules_cc side :)

"//conditions:default": ["-Wl,-S"],
}),
requires_not_none = "//cc/toolchains/variables:strip_debug_symbols",
)
12 changes: 12 additions & 0 deletions cc/toolchains/capabilities/BUILD
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Expand Up @@ -17,3 +17,15 @@ cc_tool_capability(
cc_tool_capability(
name = "supports_pic",
)

cc_tool_capability(
name = "has_configured_linker_path",
)

cc_tool_capability(
name = "targets_windows",
)

cc_tool_capability(
name = "copy_dynamic_libraries_to_binary",
)
1 change: 1 addition & 0 deletions tests/rule_based_toolchain/legacy_features_as_args/BUILD
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Expand Up @@ -32,6 +32,7 @@ compare_feature_implementation(
actual_implementation = "//cc/toolchains/args/libraries_to_link",
expected = select({
"@platforms//os:macos": "//tests/rule_based_toolchain/legacy_features_as_args:goldens/macos/libraries_to_link.textproto",
"@platforms//os:windows": "//tests/rule_based_toolchain/legacy_features_as_args:goldens/windows/libraries_to_link.textproto",
"//conditions:default": "//tests/rule_based_toolchain/legacy_features_as_args:goldens/unix/libraries_to_link.textproto",
}),
)
Expand Down
117 changes: 117 additions & 0 deletions .../rule_based_toolchain/legacy_features_as_args/goldens/windows/libraries_to_link.textproto
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@@ -0,0 +1,117 @@
enabled: false
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I did not compare this to the legacy textproto, I'm not sure how to do that, but I'm sure it will look different if the legacy assumes only MSVC

flag_sets {
actions: "c++-link-dynamic-library"
actions: "c++-link-executable"
actions: "c++-link-nodeps-dynamic-library"
actions: "lto-index-for-dynamic-library"
actions: "lto-index-for-executable"
actions: "lto-index-for-nodeps-dynamic-library"
actions: "objc-executable"
flag_groups {
flag_groups {
expand_if_available: "thinlto_param_file"
flags: "-Wl,@%{thinlto_param_file}"
}
flag_groups {
expand_if_available: "libraries_to_link"
flag_groups {
flag_groups {
expand_if_equal {
name: "libraries_to_link.type"
value: "object_file_group"
}
flag_groups {
expand_if_false: "libraries_to_link.is_whole_archive"
flags: "-Wl,--start-lib"
}
}
flag_groups {
flag_groups {
expand_if_equal {
name: "libraries_to_link.type"
value: "object_file_group"
}
flag_groups {
flag_groups {
expand_if_true: "libraries_to_link.is_whole_archive"
flags: "-Wl,/WHOLEARCHIVE:%{libraries_to_link.object_files}"
}
flag_groups {
expand_if_false: "libraries_to_link.is_whole_archive"
flags: "%{libraries_to_link.object_files}"
}
}
iterate_over: "libraries_to_link.object_files"
}
flag_groups {
expand_if_equal {
name: "libraries_to_link.type"
value: "object_file"
}
flag_groups {
flag_groups {
expand_if_true: "libraries_to_link.is_whole_archive"
flags: "-Wl,/WHOLEARCHIVE:%{libraries_to_link.name}"
}
flag_groups {
expand_if_false: "libraries_to_link.is_whole_archive"
flags: "%{libraries_to_link.name}"
}
}
}
flag_groups {
expand_if_equal {
name: "libraries_to_link.type"
value: "interface_library"
}
flag_groups {
flag_groups {
expand_if_true: "libraries_to_link.is_whole_archive"
flags: "-Wl,/WHOLEARCHIVE:%{libraries_to_link.name}"
}
flag_groups {
expand_if_false: "libraries_to_link.is_whole_archive"
flags: "%{libraries_to_link.name}"
}
}
}
flag_groups {
expand_if_equal {
name: "libraries_to_link.type"
value: "static_library"
}
flag_groups {
flag_groups {
expand_if_true: "libraries_to_link.is_whole_archive"
flags: "-Wl,/WHOLEARCHIVE:%{libraries_to_link.name}"
}
flag_groups {
expand_if_false: "libraries_to_link.is_whole_archive"
flags: "%{libraries_to_link.name}"
}
}
}
flag_groups {
expand_if_equal {
name: "libraries_to_link.type"
value: "dynamic_library"
}
flags: "-l%{libraries_to_link.name}"
}
}
flag_groups {
expand_if_equal {
name: "libraries_to_link.type"
value: "object_file_group"
}
flag_groups {
expand_if_false: "libraries_to_link.is_whole_archive"
flags: "-Wl,--end-lib"
}
}
iterate_over: "libraries_to_link"
}
}
}
}
name: "libraries_to_link_test"