This is a list of rules/macros that should be exported as documentation.
A type of action (eg. c_compile, assemble, strip).
cc_action_type
rules are used to associate arguments and tools together to perform a specific action. Bazel prescribes a set of known action types that are used to drive typical C/C++/ObjC actions like compiling, linking, and archiving. The set of well-known action types can be found in @rules_cc//cc/toolchains/actions:BUILD.
It's possible to create project-specific action types for use in toolchains. Be careful when doing this, because every toolchain that encounters the action will need to be configured to support the custom action type. If your project is a library, avoid creating new action types as it will reduce compatibility with existing toolchains and increase setup complexity for users.
Example:
load("@rules_cc//cc:action_names.bzl", "ACTION_NAMES") load("@rules_cc//cc/toolchains:actions.bzl", "cc_action_type") cc_action_type( name = "cpp_compile", action_name = = ACTION_NAMES.cpp_compile, )
ATTRIBUTES
Name | Description | Type | Mandatory | Default |
---|---|---|---|---|
name | A unique name for this target. | Name | required | |
action_name | - | String | required |
Represents a set of actions.
This is a convenience rule to allow for more compact representation of a group of action types. Use this anywhere a cc_action_type
is accepted.
Example:
load("@rules_cc//cc/toolchains:actions.bzl", "cc_action_type_set") cc_action_type_set( name = "link_executable_actions", actions = [ "@rules_cc//cc/toolchains/actions:cpp_link_executable", "@rules_cc//cc/toolchains/actions:lto_index_for_executable", ], )
ATTRIBUTES
Name | Description | Type | Mandatory | Default |
---|---|---|---|---|
name | A unique name for this target. | Name | required | |
actions | A list of cc_action_type or cc_action_type_set | List of labels | required | |
allow_empty | - | Boolean | optional | False |
An ordered list of cc_args.
This is a convenience rule to allow you to group a set of multiple cc_args
into a single list. This particularly useful for toolchain behaviors that require different flags for different actions.
Note: The order of the arguments in args
is preserved to support order-sensitive flags.
Example usage:
load("@rules_cc//cc/toolchains:cc_args.bzl", "cc_args") load("@rules_cc//cc/toolchains:args_list.bzl", "cc_args_list") cc_args( name = "gc_sections", actions = [ "@rules_cc//cc/toolchains/actions:link_actions", ], args = ["-Wl,--gc-sections"], ) cc_args( name = "function_sections", actions = [ "@rules_cc//cc/toolchains/actions:compile_actions", "@rules_cc//cc/toolchains/actions:link_actions", ], args = ["-ffunction-sections"], ) cc_args_list( name = "gc_functions", args = [ ":function_sections", ":gc_sections", ], )
ATTRIBUTES
Name | Description | Type | Mandatory | Default |
---|---|---|---|---|
name | A unique name for this target. | Name | required | |
args | (ordered) cc_args to include in this list. | List of labels | optional | [] |
A declaration that a feature with this name is defined elsewhere.
This rule communicates that a feature has been defined externally to make it possible to reference features that live outside the rule-based cc toolchain ecosystem. This allows various toolchain rules to reference the external feature without accidentally re-defining said feature.
This rule is currently considered a private API of the toolchain rules to encourage the Bazel ecosystem to migrate to properly defining their features as rules.
Example:
load("@rules_cc//cc/toolchains:external_feature.bzl", "cc_external_feature") # rules_rust defines a feature that is disabled whenever rust artifacts are being linked using # the cc toolchain to signal that incompatible flags should be disabled as well. cc_external_feature( name = "rules_rust_unsupported_feature", feature_name = "rules_rust_unsupported_feature", overridable = False, )
ATTRIBUTES
Name | Description | Type | Mandatory | Default |
---|---|---|---|---|
name | A unique name for this target. | Name | required | |
feature_name | The name of the feature | String | required | |
overridable | Whether the feature can be overridden | Boolean | required |
A dynamic set of toolchain flags that create a singular feature definition.
A feature is basically a dynamically toggleable cc_args_list
. There are a variety of dependencies and compatibility requirements that must be satisfied to enable a cc_feature
. Once those conditions are met, the arguments in cc_feature.args
are expanded and added to the command-line.
A feature may be enabled or disabled through the following mechanisms:
.bazelrc
file via the --features
flagcc_feature.implies
) where one feature may implicitly enable another.cc_library
) or package
definitions may elect to manually enable or disable features through the features
attribute.Note that a feature may alternate between enabled and disabled dynamically over the course of a build. Because of their toggleable nature, it's generally best to avoid adding arguments to a cc_toolchain
as a cc_feature
unless strictly necessary. Instead, prefer to express arguments via cc_toolchain.args
whenever possible.
You should use a cc_feature
when any of the following apply:
features = ["optimize_for_size"]
to create a small binary instead of optimizing for performance.If you only need to configure flags via the Bazel command-line, instead consider adding a bool_flag
paired with a config_setting
and then make your cc_args
rule select
on the config_setting
.
For more details about how Bazel handles features, see the official Bazel documentation at https://bazel.build/docs/cc-toolchain-config-reference#features.
Example:
load("@rules_cc//cc/toolchains:feature.bzl", "cc_feature") # A feature that enables LTO, which may be incompatible when doing interop with various # languages (e.g. rust, go), or may need to be disabled for particular `cc_binary` rules # for various reasons. cc_feature( name = "lto", feature_name = "lto", args = [":lto_args"], )
ATTRIBUTES
Name | Description | Type | Mandatory | Default |
---|---|---|---|---|
name | A unique name for this target. | Name | required | |
args | A list of cc_args or cc_args_list labels that are expanded when this feature is enabled. | List of labels | optional | [] |
feature_name | The name of the feature that this rule implements. The feature name is a string that will be used in the features attribute of rules to enable them (eg. cc_binary(..., features = ["opt"]) .While two features with the same feature_name may not be bound to the same toolchain, they can happily live alongside each other in the same BUILD file.Example: cc_feature( name = “sysroot_macos”, feature_name = “sysroot”, ... ) cc_feature( name = “sysroot_linux”, feature_name = “sysroot”, ... ) | String | optional | "" |
implies | List of features enabled along with this feature. Warning: If any of the features cannot be enabled, this feature is silently disabled. | List of labels | optional | [] |
mutually_exclusive | A list of things that this feature is mutually exclusive with. It can be either: * A feature, in which case the two features are mutually exclusive. * A cc_mutually_exclusive_category , in which case all features that write mutually_exclusive = [":category"] are mutually exclusive with each other.If this feature has a side-effect of implementing another feature, it can be useful to list that feature here to ensure they aren't enabled at the same time. | List of labels | optional | [] |
overrides | A declaration that this feature overrides a known feature. In the example below, if you missed the “overrides” attribute, it would complain that the feature “opt” was defined twice. Example: load(“@rules_cc//cc/toolchains:feature.bzl”, “cc_feature”) cc_feature( name = “opt”, feature_name = “opt”, args = [“:size_optimized”], overrides = “@rules_cc//cc/toolchains/features:opt”, ) | Label | optional | None |
requires_any_of | A list of feature sets that define toolchain compatibility. If at least one of the listed cc_feature_set s are fully satisfied (all features exist in the toolchain AND are currently enabled), this feature is deemed compatible and may be enabled.Note: Even if cc_feature.requires_any_of is satisfied, a feature is not enabled unless another mechanism (e.g. command-line flags, cc_feature.implies , cc_toolchain_config.enabled_features ) signals that the feature should actually be enabled. | List of labels | optional | [] |
Defines a compound relationship between features.
This rule can be used with cc_args.require_any_of
to specify that a set of arguments are only enabled when a constraint is met. Both all_of
and none_of
must be satisfied simultaneously.
This is basically a cc_feature_set
that supports none_of
expressions. This extra flexibility is why this rule may only be used by cc_args.require_any_of
.
Example:
load("@rules_cc//cc/toolchains:feature_constraint.bzl", "cc_feature_constraint") # A constraint that requires a `linker_supports_thinlto` feature to be enabled, # AND a `no_optimization` to be disabled. cc_feature_constraint( name = "thinlto_constraint", all_of = [":linker_supports_thinlto"], none_of = [":no_optimization"], )
ATTRIBUTES
Name | Description | Type | Mandatory | Default |
---|---|---|---|---|
name | A unique name for this target. | Name | required | |
all_of | - | List of labels | optional | [] |
none_of | - | List of labels | optional | [] |
Defines a set of features.
This may be used by both cc_feature
and cc_args
rules, and is effectively a way to express a logical AND
operation across multiple required features.
Example:
load("@rules_cc//cc/toolchains:feature_set.bzl", "cc_feature_set") cc_feature_set( name = "thin_lto_requirements", all_of = [ ":thin_lto", ":opt", ], )
ATTRIBUTES
Name | Description | Type | Mandatory | Default |
---|---|---|---|---|
name | A unique name for this target. | Name | required | |
all_of | A set of features | List of labels | optional | [] |
A rule used to categorize cc_feature
definitions for which only one can be enabled.
This is used by cc_feature.mutually_exclusive
to express groups of cc_feature
definitions that are inherently incompatible with each other and must be treated as mutually exclusive.
Warning: These groups are keyed by name, so two cc_mutually_exclusive_category
definitions of the same name in different packages will resolve to the same logical group.
Example:
load("@rules_cc//cc/toolchains:feature.bzl", "cc_feature") load("@rules_cc//cc/toolchains:mutually_exclusive_category.bzl", "cc_mutually_exclusive_category") cc_mutually_exclusive_category( name = "opt_level", ) cc_feature( name = "speed_optimized", mutually_exclusive = [":opt_level"], ) cc_feature( name = "size_optimized", mutually_exclusive = [":opt_level"], ) cc_feature( name = "unoptimized", mutually_exclusive = [":opt_level"], )
ATTRIBUTES
Name | Description | Type | Mandatory | Default |
---|---|---|---|---|
name | A unique name for this target. | Name | required |
Declares a tool for use by toolchain actions.
cc_tool
rules are used in a cc_tool_map
rule to ensure all files and metadata required to run a tool are available when constructing a cc_toolchain
.
In general, include all files that are always required to run a tool (e.g. libexec/** and cross-referenced tools in bin/*) in the data attribute. If some files are only required when certain flags are passed to the tool, consider using a cc_args
rule to bind the files to the flags that require them. This reduces the overhead required to properly enumerate a sandbox with all the files required to run a tool, and ensures that there isn't unintentional leakage across configurations and actions.
Example:
load("@rules_cc//cc/toolchains:tool.bzl", "cc_tool") cc_tool( name = "clang_tool", executable = "@llvm_toolchain//:bin/clang", # Suppose clang needs libc to run. data = ["@llvm_toolchain//:lib/x86_64-linux-gnu/libc.so.6"] tags = ["requires-network"], capabilities = ["@rules_cc//cc/toolchains/capabilities:supports_pic"], )
ATTRIBUTES
Name | Description | Type | Mandatory | Default |
---|---|---|---|---|
name | A unique name for this target. | Name | required | |
src | The underlying binary that this tool represents. Usually just a single prebuilt (eg. @toolchain//:bin/clang), but may be any executable label. | Label | optional | None |
data | Additional files that are required for this tool to run. Frequently, clang and gcc require additional files to execute as they often shell out to other binaries (e.g. cc1 ). | List of labels | optional | [] |
allowlist_include_directories | Include paths implied by using this tool. Compilers may include a set of built-in headers that are implicitly available unless flags like -nostdinc are provided. Bazel checks that all included headers are properly provided by a dependency or allowlisted through this mechanism.As a rule of thumb, only use this if Bazel is complaining about absolute paths in your toolchain and you've ensured that the toolchain is compiling with the -no-canonical-prefixes and/or -fno-canonical-system-headers arguments.This can help work around errors like: the source file 'main.c' includes the following non-builtin files with absolute paths (if these are builtin files, make sure these paths are in your toolchain) . | List of labels | optional | [] |
capabilities | Declares that a tool is capable of doing something. For example, @rules_cc//cc/toolchains/capabilities:supports_pic . | List of labels | optional | [] |
A capability is an optional feature that a tool supports.
For example, not all compilers support PIC, so to handle this, we write:
cc_tool( name = "clang", src = "@host_tools/bin/clang", capabilities = [ "@rules_cc//cc/toolchains/capabilities:supports_pic", ], ) cc_args( name = "pic", requires = [ "@rules_cc//cc/toolchains/capabilities:supports_pic" ], args = ["-fPIC"], )
This ensures that -fPIC
is added to the command-line only when we are using a tool that supports PIC.
ATTRIBUTES
Name | Description | Type | Mandatory | Default |
---|---|---|---|---|
name | A unique name for this target. | Name | required | |
feature_name | The name of the feature to generate for this capability | String | optional | "" |
Action-specific arguments for use with a cc_toolchain
.
This rule is the fundamental building building block for every toolchain tool invocation. Each argument expressed in a toolchain tool invocation (e.g. gcc
, llvm-ar
) is declared in a cc_args
rule that applies an ordered list of arguments to a set of toolchain actions. cc_args
rules can be added unconditionally to a cc_toolchain
, conditionally via select()
statements, or dynamically via an intermediate cc_feature
.
Conceptually, this is similar to the old CFLAGS
, CPPFLAGS
, etc. environment variables that many build systems use to determine which flags to use for a given action. The significant difference is that cc_args
rules are declared in a structured way that allows for significantly more powerful and sharable toolchain configurations. Also, due to Bazel‘s more granular action types, it’s possible to bind flags to very specific actions (e.g. LTO indexing for an executable vs a dynamic library) multiple different actions (e.g. C++ compile and link simultaneously).
Example usage:
load("@rules_cc//cc/toolchains:args.bzl", "cc_args") # Basic usage: a trivial flag. # # An example of expressing `-Werror` as a [`cc_args`](#cc_args) rule. cc_args( name = "warnings_as_errors", actions = [ # Applies to all C/C++ compile actions. "@rules_cc//cc/toolchains/actions:compile_actions", ], args = ["-Werror"], ) # Basic usage: ordered flags. # # An example of linking against libc++, which uses two flags that must be applied in order. cc_args( name = "link_libcxx", actions = [ # Applies to all link actions. "@rules_cc//cc/toolchains/actions:link_actions", ], # On tool invocation, this appears as `-Xlinker -lc++`. Nothing will ever end up between # the two flags. args = [ "-Xlinker", "-lc++", ], ) # Advanced usage: built-in variable expansions. # # Expands to `-L/path/to/search_dir` for each directory in the built-in variable # `library_search_directories`. This variable is managed internally by Bazel through inherent # behaviors of Bazel and the interactions between various C/C++ build rules. cc_args( name = "library_search_directories", actions = [ "@rules_cc//cc/toolchains/actions:link_actions", ], args = ["-L{search_dir}"], iterate_over = "@rules_cc//cc/toolchains/variables:library_search_directories", requires_not_none = "@rules_cc//cc/toolchains/variables:library_search_directories", format = { "search_dir": "@rules_cc//cc/toolchains/variables:library_search_directories", }, )
For more extensive examples, see the usages here: https://github.com/bazelbuild/rules_cc/tree/main/cc/toolchains/args
PARAMETERS
Name | Description | Default Value |
---|---|---|
name | (str) The name of the target. | none |
actions | (List[Label]) A list of labels of cc_action_type or cc_action_type_set rules that dictate which actions these arguments should be applied to. | None |
allowlist_include_directories | (List[Label]) A list of include paths that are implied by using this rule. These must point to a skylib directory or subdirectory rule. Some flags (e.g. --sysroot) imply certain include paths are available despite not explicitly specifying a normal include path flag (-I , -isystem , etc.). Bazel checks that all included headers are properly provided by a dependency or allowlisted through this mechanism.As a rule of thumb, only use this if Bazel is complaining about absolute paths in your toolchain and you've ensured that the toolchain is compiling with the -no-canonical-prefixes and/or -fno-canonical-system-headers arguments.This can help work around errors like: the source file 'main.c' includes the following non-builtin files with absolute paths (if these are builtin files, make sure these paths are in your toolchain) . | None |
args | (List[str]) The command-line arguments that are applied by using this rule. This is mutually exclusive with nested. | None |
data | (List[Label]) A list of runtime data dependencies that are required for these arguments to work as intended. | None |
env | (Dict[str, str]) Environment variables that should be set when the tool is invoked. | None |
format | (Dict[str, Label]) A mapping of format strings to the label of the corresponding cc_variable that the value should be pulled from. All instances of {variable_name} will be replaced with the expanded value of variable_name in this dictionary. The complete list of possible variables can be found in https://github.com/bazelbuild/rules_cc/tree/main/cc/toolchains/variables/BUILD. It is not possible to declare custom variables--these are inherent to Bazel itself. | {} |
iterate_over | (Label) The label of a cc_variable that should be iterated over. This is intended for use with built-in variables that are lists. | None |
nested | (List[Label]) A list of cc_nested_args rules that should be expanded to command-line arguments when this rule is used. This is mutually exclusive with args. | None |
requires_not_none | (Label) The label of a cc_variable that should be checked for existence before expanding this rule. If the variable is None, this rule will be ignored. | None |
requires_none | (Label) The label of a cc_variable that should be checked for non-existence before expanding this rule. If the variable is not None, this rule will be ignored. | None |
requires_true | (Label) The label of a cc_variable that should be checked for truthiness before expanding this rule. If the variable is false, this rule will be ignored. | None |
requires_false | (Label) The label of a cc_variable that should be checked for falsiness before expanding this rule. If the variable is true, this rule will be ignored. | None |
requires_equal | (Label) The label of a cc_variable that should be checked for equality before expanding this rule. If the variable is not equal to (requires_equal_value)[#cc_args-requires_equal_value], this rule will be ignored. | None |
requires_equal_value | (str) The value to compare (requires_equal)[#cc_args-requires_equal] against. | None |
requires_any_of | (List[Label]) These arguments will be used in a tool invocation when at least one of the cc_feature_constraint entries in this list are satisfied. If omitted, this flag set will be enabled unconditionally. | None |
kwargs | common attributes that should be applied to this rule. | none |
Nested arguments for use in more complex cc_args
expansions.
While this rule is very similar in shape to cc_args
, it is intended to be used as a dependency of cc_args
to provide additional arguments that should be applied to the same actions as defined by the parent cc_args
rule. The key motivation for this rule is to allow for more complex variable-based argument expensions.
Prefer expressing collections of arguments as cc_args
and cc_args_list
rules when possible.
For living examples of how this rule is used, see the usages here: https://github.com/bazelbuild/rules_cc/tree/main/cc/toolchains/args/runtime_library_search_directories/BUILD https://github.com/bazelbuild/rules_cc/tree/main/cc/toolchains/args/libraries_to_link/BUILD
Note: These examples are non-trivial, but they illustrate when it is absolutely necessary to use this rule.
PARAMETERS
Name | Description | Default Value |
---|---|---|
name | (str) The name of the target. | none |
args | (List[str]) The command-line arguments that are applied by using this rule. This is mutually exclusive with nested. | None |
data | (List[Label]) A list of runtime data dependencies that are required for these arguments to work as intended. | None |
format | (Dict[str, Label]) A mapping of format strings to the label of the corresponding cc_variable that the value should be pulled from. All instances of {variable_name} will be replaced with the expanded value of variable_name in this dictionary. The complete list of possible variables can be found in https://github.com/bazelbuild/rules_cc/tree/main/cc/toolchains/variables/BUILD. It is not possible to declare custom variables--these are inherent to Bazel itself. | {} |
iterate_over | (Label) The label of a cc_variable that should be iterated over. This is intended for use with built-in variables that are lists. | None |
nested | (List[Label]) A list of cc_nested_args rules that should be expanded to command-line arguments when this rule is used. This is mutually exclusive with args. | None |
requires_not_none | (Label) The label of a cc_variable that should be checked for existence before expanding this rule. If the variable is None, this rule will be ignored. | None |
requires_none | (Label) The label of a cc_variable that should be checked for non-existence before expanding this rule. If the variable is not None, this rule will be ignored. | None |
requires_true | (Label) The label of a cc_variable that should be checked for truthiness before expanding this rule. If the variable is false, this rule will be ignored. | None |
requires_false | (Label) The label of a cc_variable that should be checked for falsiness before expanding this rule. If the variable is true, this rule will be ignored. | None |
requires_equal | (Label) The label of a cc_variable that should be checked for equality before expanding this rule. If the variable is not equal to (requires_equal_value)[#cc_nested_args-requires_equal_value], this rule will be ignored. | None |
requires_equal_value | (str) The value to compare (requires_equal)[#cc_nested_args-requires_equal] against. | None |
kwargs | common attributes that should be applied to this rule. | none |
A toolchain configuration rule that maps toolchain actions to tools.
A cc_tool_map
aggregates all the tools that may be used for a given toolchain and maps them to their corresponding actions. Conceptually, this is similar to the CXX=/path/to/clang++
environment variables that most build systems use to determine which tools to use for a given action. To simplify usage, some actions have been grouped together (for example, @rules_cc//cc/toolchains/actions:cpp_compile_actions) to logically express “all the C++ compile actions”.
In Bazel, there is a little more granularity to the mapping, so the mapping doesn't follow the traditional CXX
, AR
, etc. naming scheme. For a comprehensive list of all the well-known actions, see @rules_cc//cc/toolchains/actions:BUILD.
Example usage:
load("@rules_cc//cc/toolchains:tool_map.bzl", "cc_tool_map") cc_tool_map( name = "all_tools", tools = { "@rules_cc//cc/toolchains/actions:assembly_actions": ":asm", "@rules_cc//cc/toolchains/actions:c_compile": ":clang", "@rules_cc//cc/toolchains/actions:cpp_compile_actions": ":clang++", "@rules_cc//cc/toolchains/actions:link_actions": ":lld", "@rules_cc//cc/toolchains/actions:objcopy_embed_data": ":llvm-objcopy", "@rules_cc//cc/toolchains/actions:strip": ":llvm-strip", "@rules_cc//cc/toolchains/actions:ar_actions": ":llvm-ar", }, )
PARAMETERS
Name | Description | Default Value |
---|---|---|
name | (str) The name of the target. | none |
tools | (Dict[Label, Label]) A mapping between cc_action_type /cc_action_type_set targets and the cc_tool or executable target that implements that action. | none |
kwargs | common attributes that should be applied to this rule. | none |
A C/C++ toolchain configuration.
This rule is the core declaration of a complete C/C++ toolchain. It collects together tool configuration, which arguments to pass to each tool, and how features (dynamically-toggleable argument lists) interact.
A single cc_toolchain
may support a wide variety of platforms and configurations through configurable build attributes and feature relationships.
Arguments are applied to commandline invocation of tools in the following order:
args
.known_features
.When building a cc_toolchain
configuration, it's important to understand how select
statements will be evaluated:
cc_toolchain
are evaluated under the target platform. This means that a //third_party/bazel_platforms/os:linux
constraint will be satisfied when the final compiled binaries are intended to be ran from a Linux machine. This means that a different operating system (e.g. Windows) may be cross-compiling to linux.cc_tool_map
rule performs a transition to the exec platform when evaluating tools. This means that a if a //third_party/bazel_platforms/os:linux
constraint is satisfied in a select
statement on a cc_tool
, that means the machine that will run the tool is a Linux machine. This means that a Linux machine may be cross-compiling to a different OS like Windows.Generated rules: {name}: A cc_toolchain
for this toolchain. _{name}_config: A cc_toolchain_config
for this toolchain. {name}*_files: Generated rules that group together files for “ar_files”, “as_files”, “compiler_files”, “coverage_files”, “dwp_files”, “linker_files”, “objcopy_files”, and “strip_files” normally enumerated as part of the cc_toolchain
rule.
PARAMETERS
Name | Description | Default Value |
---|---|---|
name | (str) The name of the label for the toolchain. | none |
tool_map | (Label) The cc_tool_map that specifies the tools to use for various toolchain actions. | None |
args | (List[Label]) A list of cc_args and cc_arg_list to apply across this toolchain. | [] |
known_features | (List[Label]) A list of cc_feature rules that this toolchain supports. Whether or not these features are enabled may change over the course of a build. See the documentation for cc_feature for more information. | [] |
enabled_features | (List[Label]) A list of cc_feature rules whose initial state should be enabled . Note that it is still possible for these features to be disabled over the course of a build through other mechanisms. See the documentation for cc_feature for more information. | [] |
libc_top | (Label) A collection of artifacts for libc passed as inputs to compile/linking actions. See cc_toolchain.libc_top for more information. | None |
module_map | (Label) Module map artifact to be used for modular builds. See cc_toolchain.module_map for more information. | None |
dynamic_runtime_lib | (Label) Dynamic library to link when the static_link_cpp_runtimes and dynamic_linking_mode features are both enabled. See cc_toolchain.dynamic_runtime_lib for more information. | None |
static_runtime_lib | (Label) Static library to link when the static_link_cpp_runtimes and static_linking_mode features are both enabled. See cc_toolchain.dynamic_runtime_lib for more information. | None |
supports_header_parsing | (bool) Whether or not this toolchain supports header parsing actions. See cc_toolchain.supports_header_parsing for more information. | False |
supports_param_files | (bool) Whether or not this toolchain supports linking via param files. See cc_toolchain.supports_param_files for more information. | False |
kwargs | common attributes that should be applied to all rules created by this macro. | none |
Exposes a toolchain variable to use in toolchain argument expansions.
This internal rule exposes toolchain variables that may be expanded in cc_args
or cc_nested_args
rules. Because these varaibles merely expose variables inherrent to Bazel, it's not possible to declare custom variables.
For a full list of available variables, see @rules_cc//cc/toolchains/varaibles:BUILD.
Example:
load("@rules_cc//cc/toolchains/impl:variables.bzl", "cc_variable") # Defines two targets, ":foo" and ":foo.bar" cc_variable( name = "foo", type = types.list(types.struct(bar = types.string)), )
PARAMETERS
Name | Description | Default Value |
---|---|---|
name | (str) The name of the outer variable, and the rule. | none |
type | The type of the variable, constructed using types factory in @rules_cc//cc/toolchains/impl:variables.bzl. | none |
kwargs | common attributes that should be applied to this rule. | none |