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Toolchain Features

These are the cc_toolchain features defined by the toolchain configs in templates/linux/cc_toolchain_config.bzl.template and templates/qnx/cc_toolchain_config.bzl.template.

Both toolchains enable no_legacy_features, which turns off the features Bazel would otherwise add implicitly. As a result every flag the toolchain emits comes from a feature defined explicitly below.

Migrating from an implicit/legacy setup? See the Migration guide for the behavioral impact of no_legacy_features and how to restore supported behavior explicitly.

Each entry is tagged with the platform(s) it applies to: (both), (Linux), or (QNX). Unless noted as opt-in (disabled by default), a feature is enabled by default.

Note: The order of features in the features list is significant — flags from a later feature appear after those from an earlier feature on the command line.

Capability markers

  • no_legacy_features (both) — Disables Bazel's implicit legacy features.
  • supports_pic (both) — Declares position-independent-code support.
  • supports_dynamic_linker (both) — Declares dynamic-linking support.
  • supports_fission (Linux) — Declares Fission (split DWARF) support.
  • supports_header_path_normalization (Linux) — Suppresses absolute-path warnings for system headers.
  • dbg / opt (both) — Well-known build-mode markers used to select flags.

Compilation

  • unfiltered_compile_flags (both) — Redacts __DATE__/__TIME__/__TIMESTAMP__ for reproducible builds.
  • default_compile_flags (both) — Core compile flags plus dbg/opt build-mode variants (exact flags differ per target).
  • pic (Linux) — Emits -fPIC when the pic build variable is available. QNX declares the supports_pic capability marker but does not add -fPIC in the default compile flags.
  • random_seed (both) — Emits -frandom-seed=<output_file> for deterministic output.
  • include_paths (both) — Emits -iquote / -I / -isystem from the quote_include_paths, include_paths, and system_include_paths variables.
  • preprocessor_defines (both) — Emits -D defines (from defines / local_defines).
  • includes (Linux) — Emits -include <hdr> for force-included headers.
  • user_compile_flags (both) — Passes through user-supplied compile flags (copts).
  • compiler_input_flags (both) — -c and the source file.
  • compiler_output_flags (both) — -S / -E / -o output flags.
  • compiler_library_search_paths (Linux) — Sets LD_LIBRARY_PATH so the compiler binary finds its shared libraries.
  • dependency_file (both) — Generates .d dependency files. On QNX, dependency_file_named_implicitly toggles between explicit and implicit naming.
  • per_object_debug_info (Linux) — Emits -gsplit-dwarf -g under --fission (guarded; no-op otherwise).

Linking / archiving

  • archiver_flags (both) — ar flags (rcsD) and the object-file list for static archives.
  • user_link_flags (both) — Passes through user-supplied link flags (linkopts).
  • linker_param_file (both) — Uses @param_file for linker/archiver args.
  • default_link_flags (both) — Default/hardening link flags (exact flags differ per target and build mode).
  • library_search_directories (both) — Emits -L search paths.
  • runtime_library_search_directories (both) — Emits -Wl,-rpath entries ($ORIGIN for cc_test, $EXEC_ORIGIN otherwise).
  • shared_flag (both) — -shared for dynamic libraries.
  • output_execpath_flags (both) — -o for the link output.
  • libraries_to_link (both) — Handles whole-archive, static, object-file, dynamic, and versioned-dynamic library linking.
  • sysroot_link_flags (Linux) — Adds --sysroot / -Wl,--sysroot at link.

Opt-in link features (Linux)

These mirror Bazel's legacy features and are guarded, so they are no-ops until the relevant build mode is active. All are enabled by default except where noted.

  • fission_support — -Wl,--gdb-index under --fission.
  • linkstamps — Passes %{linkstamp_paths} to the linker (--stamp).
  • force_pic_flags — -pie for executables under --force_pic.
  • strip_debug_symbols — -Wl,-S when the link output is stripped (e.g. fastbuild/opt, not dbg).
  • static_libgcc — -static-libgcc when static_link_cpp_runtimes is on.
  • fully_static_link — -static for fully static executables. Opt-in (disabled by default), since it forces static linking for every target and requires static system archives (unavailable on some toolchains, e.g. AutoSD).

Warnings

Opt-in / disabled by default unless noted otherwise.

  • minimal_warnings (both) — Baseline warning set (includes -Wall). Enabled by default on QNX; opt-in (disabled by default) on Linux.
  • strict_warnings (both) — Stricter warnings; implies minimal_warnings.
  • all_wall_warnings (Linux) — Broadest warning set; implies strict_warnings.
  • 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.

Threading

  • use_pthread (Linux) — Links with -pthread.

Extra flag hooks (template-substituted)

  • extra_compile_flags (both) — Extra flags for all compile actions.
  • extra_c_compile_flags / extra_cxx_compile_flags (Linux) — Extra C / C++ compile flags.
  • extra_link_flags (both) — Extra link flags.

Coverage

  • coverage (both) — Base coverage feature.
  • gcc_coverage_map_format (both) — -fprofile-arcs -ftest-coverage at compile and -lgcov / --coverage at link.

QNX environment

  • sdp_env (QNX) — Injects QNX SDP environment variables (QNX_HOST, QNX_TARGET, license path, ...) into compile/link actions.
  • qnx_license_env_info (QNX) — Adds an optional license environment entry.