Add feature injection

docs/extension_api.md

@@ -72,6 +72,8 @@ Flag and runtime attributes:
 - `extra_c_compile_flags`
 - `extra_cxx_compile_flags`
 - `extra_link_flags`
+- `extra_known_features`
+- `extra_enabled_features`
 - `ld_library_paths`
 - `runtime_ecosystem`
 - `use_base_constraints_only`
@@ -93,6 +95,21 @@ attributes are:
 - `sha256`: sha256 of the archive
 - `strip_prefix`: extraction prefix for packaged archives
 
+## Feature Injection
+
+`extra_known_features` and `extra_enabled_features` let a workspace add
+rule-based `cc_feature` targets (defined outside this repository) to the
+generated toolchain:
+
+- `extra_known_features` — registers external features so they can be toggled
+  per target via the `features` attribute or build-wide via `--features`.
+- `extra_enabled_features` — registers *and* enables external features by
+  default.
+
+Sanitizers are the primary use case: they are defined by the
+`score_cpp_policies` module and brought into the toolchain through these
+attributes. See [Toolchain features](features.md#sanitizers-linux-opt-in).
+
 
 ## Activation In A Workspace
 
@@ -120,5 +137,10 @@ behavior explicitly, see the
 - The extension is intended for the root module.
 - When `use_default_package` is enabled, the version matrix can inject extra
   include and link flags required by non-standard sysroot layouts.
+- Sanitizer features are not registered automatically. They are defined by the
+  `score_cpp_policies` module and made available through *feature injection* —
+  the `extra_known_features` / `extra_enabled_features` attributes on
+  `gcc.toolchain(...)`. See [Toolchain features](features.md#sanitizers-linux-opt-in)
+  for the injected feature names.
 - QNX toolchains use additional licensing and include-path parameters that do
   not apply to Linux toolchains.

docs/features.md

@@ -96,9 +96,18 @@ Opt-in / disabled by default unless noted otherwise.
 - **`warnings_as_errors`** (both) — Adds `-Werror`.
 
 ## Sanitizers (Linux, opt-in)
-- **`sanitizer`** — Base sanitizer feature.
-- **`asan`** / **`lsan`** / **`tsan`** / **`ubsan`** — Address / Leak / Thread /
-  Undefined-Behavior sanitizers; each implies `sanitizer`.
+Sanitizers are **not** defined by this toolchain. They are provided as
+rule-based `cc_feature` definitions by the `score_cpp_policies` module and made
+available through *feature injection* — the `extra_known_features` /
+`extra_enabled_features` attributes on `gcc.toolchain(...)`. Once injected they
+behave like any other opt-in feature.
+
+- **`score_asan`** — AddressSanitizer (`-fsanitize=address`).
+- **`score_lsan`** — LeakSanitizer (`-fsanitize=leak`).
+- **`score_tsan`** — ThreadSanitizer (`-fsanitize=thread`).
+- **`score_ubsan`** — UndefinedBehaviorSanitizer (`-fsanitize=undefined`).
+
+See the `score_cpp_policies` documentation for the authoritative list and usage.
 
 ## Threading
 - **`use_pthread`** (Linux) — Links with `-pthread`.

docs/migration_guide.md

@@ -97,22 +97,26 @@ toolchain, are summarized below.
 | `gcov` | **Supported, wiring** | `tool_paths` (`gcov_wrapper`) |
 | Warnings (e.g. `-Wall`) added by default | **Linux: opt-in · QNX: on by default** | `minimal_warnings` (includes `-Wall`) is enabled by default on QNX but disabled on Linux. `strict_warnings` / `all_wall_warnings` are opt-in on both. |
 | `-Werror` | **Not implicit — opt-in** | `warnings_as_errors` (disabled by default) |
-| Sanitizers (asan/lsan/tsan/ubsan) | **Not implicit — opt-in (Linux)** | `asan` / `lsan` / `tsan` / `ubsan` (disabled by default) |
+| Sanitizers (asan/lsan/tsan/ubsan) | **Not part of this toolchain — injected (Linux)** | Defined by `score_cpp_policies` (`score_asan` / `score_lsan` / `score_tsan` / `score_ubsan`) and brought in via `extra_known_features` / `extra_enabled_features` |
 | Fully static link (`-static`) | **Not implicit — opt-in** | `fully_static_link` (disabled by default) |
 | `-pthread` | **Not implicit — opt-in (Linux)** | `use_pthread` (disabled by default) |
 | Fission / split DWARF, linkstamps, strip, static-libgcc | **Supported, guarded** | Guarded features; no-ops until the relevant build mode is active |
 | Any other Bazel legacy default not listed above | **Not available** | Must be added explicitly (see below) |
 
-Two categories deserve special attention because they are the most frequent
+Three categories deserve special attention because they are the most frequent
 migration surprises:
 
 1. **Warnings differ by platform.** On **Linux**, all warning features are
    opt-in — if you expected `-Wall`-style warnings you must enable them. On
    **QNX**, `minimal_warnings` (which includes `-Wall`) is enabled by default,
    so those warnings do *not* disappear; `strict_warnings`,
    `all_wall_warnings`, and `-Werror` remain opt-in on both platforms.
-2. **`-pthread`, sanitizers, and fully-static linking are opt-in.** These emit
-   nothing until you enable the corresponding feature.
+2. **`-pthread` and fully-static linking are opt-in.** These emit nothing until
+   you enable the corresponding feature.
+3. **Sanitizers are not part of this toolchain.** They are defined by the
+   `score_cpp_policies` module and must first be injected via
+   `extra_known_features` / `extra_enabled_features` before they can be enabled.
+   See [Toolchain features](features.md#sanitizers-linux-opt-in).
 
 For the authoritative and complete list, always refer to
 [Toolchain features](features.md).
@@ -155,10 +159,12 @@ build:myconfig --host_features=use_pthread
 ### 3. Turn on an opt-in feature that already exists
 
 Many legacy-equivalent behaviors already ship as opt-in features (warnings,
-sanitizers, `fully_static_link`, `use_pthread`, `per_object_debug_info`, ...).
+`fully_static_link`, `use_pthread`, `per_object_debug_info`, ...).
 You do not need to modify the toolchain to use them — enable them with
 mechanism 1 or 2 above. See the *Opt-in* entries in
-[Toolchain features](features.md).
+[Toolchain features](features.md). (Sanitizers are the exception: they are
+defined by `score_cpp_policies` and must first be injected via
+`extra_known_features` / `extra_enabled_features`.)
 
 ### 4. Inject raw flags through the toolchain attributes
 

extensions/gcc.bzl

@@ -78,6 +78,26 @@ _attrs_tc = {
         default = [],
         doc = "List of additional flags to be passed to linker.",
     ),
+    "extra_enabled_features": attr.label_list(
+        mandatory = False,
+        default = [],
+        doc = ("Extra `cc_feature` features to add to this toolchain in an initially " +
+               "enabled state. This attribute has limited integration with `cc_feature`, " +
+               "and does not run additional correctness checks or handle things like `data` " +
+               "files. This is only offered as a migration bridge for projects transitioning " +
+               "to rule-based toolchain configurations, or sharing of simple argument sets " +
+               "with older toolchains."),
+    ),
+    "extra_known_features": attr.label_list(
+        mandatory = False,
+        default = [],
+        doc = ("Extra `cc_feature` features to add to this toolchain in an initially " +
+               "disabled state. This attribute has limited integration with `cc_feature`, " +
+               "and does not run additional correctness checks or handle things like `data` " +
+               "files. This is only offered as a migration bridge for projects transitioning " +
+               "to rule-based toolchain configurations, or sharing of simple argument sets " +
+               "with older toolchains."),
+    ),
     "license_info_url": attr.string(
         default = "",
         mandatory = False,
@@ -197,6 +217,8 @@ def _get_toolchains(tags):
             "tc_extra_compile_flags": tag.extra_compile_flags,
             "tc_extra_cxx_compile_flags": tag.extra_cxx_compile_flags,
             "tc_extra_link_flags": tag.extra_link_flags,
+            "tc_extra_known_features": tag.extra_known_features,
+            "tc_extra_enabled_features": tag.extra_enabled_features,
             "tc_license_info_url": tag.license_info_url,
             "tc_license_info_variable": tag.license_info_variable,
             "tc_license_path": tag.license_path,
@@ -377,6 +399,8 @@ def _impl(mctx):
             extra_compile_flags = toolchain_info["tc_extra_compile_flags"],
             extra_c_compile_flags = toolchain_info["tc_extra_c_compile_flags"],
             extra_cxx_compile_flags = toolchain_info["tc_extra_cxx_compile_flags"],
+            extra_known_features = toolchain_info["tc_extra_known_features"],
+            extra_enabled_features = toolchain_info["tc_extra_enabled_features"],
             extra_link_flags = toolchain_info["tc_extra_link_flags"],
             license_info_variable = toolchain_info["tc_license_info_variable"],
             license_info_value = toolchain_info["tc_license_info_url"],

rules/common.bzl

@@ -51,3 +51,14 @@ def get_flag_group(flags):
             ),
         ]
     return []
+
+def label_list_to_string(input_list):
+    """ Small helper function to transform label list into string list
+
+    Args:
+        input_list (list[labels]): A list of Bazel labels.
+
+    Returns:
+        str: Formatted string
+    """
+    return "[{}]".format(", ".join(["\"{}\"".format(item) for item in input_list]))

rules/gcc.bzl

@@ -14,7 +14,7 @@
 """ Module rule for defining GCC toolchains in Bazel.
 """
 
-load("@score_bazel_cpp_toolchains//rules:common.bzl", "SDP_VERSION_MAPPING", "get_flag_groups")
+load("@score_bazel_cpp_toolchains//rules:common.bzl", "SDP_VERSION_MAPPING", "get_flag_groups", "label_list_to_string")
 
 # Constants
 _OS_QNX = "qnx"
@@ -71,12 +71,16 @@ cc_toolchain_config(
     sysroot = "@{tc_pkg_repo}//:sysroot_dir",
     target_cpu = "{tc_cpu}",
     target_os = "{tc_os}",
+    extra_known_features = {tc_extra_known_features},
+    extra_enabled_features = {tc_extra_enabled_features},
     visibility = ["//visibility:public"],
 )
 """.format(
         tc_pkg_repo = rctx.attr.tc_pkg_repo,
         tc_cpu = rctx.attr.tc_cpu,
         tc_os = rctx.attr.tc_os,
+        tc_extra_known_features = label_list_to_string(rctx.attr.extra_known_features),
+        tc_extra_enabled_features = label_list_to_string(rctx.attr.extra_enabled_features),
     )
 
 def _get_cc_config_qnx(rctx):
@@ -109,12 +113,16 @@ cc_toolchain_config(
     cxx_builtin_include_directories = "@{tc_pkg_repo}//:cxx_builtin_include_directories",
     target_cpu = "{tc_cpu}",
     target_os = "{tc_os}",
+    extra_known_features = {tc_extra_known_features},
+    extra_enabled_features = {tc_extra_enabled_features},
     visibility = ["//visibility:public"],
 )
 """.format(
         tc_pkg_repo = rctx.attr.tc_pkg_repo,
         tc_cpu = rctx.attr.tc_cpu,
         tc_os = rctx.attr.tc_os,
+        tc_extra_known_features = label_list_to_string(rctx.attr.extra_known_features),
+        tc_extra_enabled_features = label_list_to_string(rctx.attr.extra_enabled_features),
     )
 
 def _normalize_cpu(cpu):
@@ -318,6 +326,8 @@ gcc_toolchain = repository_rule(
         "extra_c_compile_flags": attr.string_list(doc = "Extra/Additional C-specific compile flags."),
         "extra_compile_flags": attr.string_list(doc = "Extra/Additional compile flags."),
         "extra_cxx_compile_flags": attr.string_list(doc = "Extra/Additional C++-specific compile flags."),
+        "extra_known_features": attr.label_list(doc = "Extra/Additional C++ FeatureInfo provider list"),
+        "extra_enabled_features": attr.label_list(doc = "Extra/Additional C++ FeatureInfo provider list enabled by default"),
         "extra_link_flags": attr.string_list(doc = "Extra/Additional link flags."),
         "gcc_version": attr.string(doc = "GCC version string"),
         "use_base_constraints_only": attr.bool(doc = "Boolean flag to state only base constraints should be used for toolchain compatibility definition"),