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# Copyright 2015 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
declare_args() {
# Compile for Address Sanitizer to find memory bugs.
is_asan = false
# Compile for Hardware-Assisted Address Sanitizer to find memory bugs
# (android/arm64 only).
# See
is_hwasan = false
# Compile for Leak Sanitizer to find leaks.
is_lsan = false
# Compile for Memory Sanitizer to find uninitialized reads.
is_msan = false
# Compile for Thread Sanitizer to find threading bugs.
is_tsan = false
# Compile for Undefined Behaviour Sanitizer to find various types of
# undefined behaviour (excludes vptr checks).
is_ubsan = false
# Halt the program if a problem is detected.
is_ubsan_no_recover = false
# Compile for Undefined Behaviour Sanitizer's null pointer checks.
is_ubsan_null = false
# Track where uninitialized memory originates from. From fastest to slowest:
# 0 - no tracking, 1 - track only the initial allocation site, 2 - track the
# chain of stores leading from allocation site to use site.
msan_track_origins = 2
# Use dynamic libraries instrumented by one of the sanitizers instead of the
# standard system libraries. Set this flag to build the libraries from source.
use_locally_built_instrumented_libraries = false
# Compile with Control Flow Integrity to protect virtual calls and casts.
# See
# TODO(pcc): Remove this flag if/when CFI is enabled in all official builds.
# Disable this on linux-chromeos to avoid using ThinLTO there;
# Similarly, don't use this on ARC builds.
# TODO( Reassess the validity of the next expression.
is_cfi =
is_official_build &&
(((target_os == "linux" || is_chromeos_lacros) && target_cpu == "x64") ||
((is_chromeos_ash || is_chromeos_lacros) && is_chromeos_device))
# Enable checks for indirect function calls via a function pointer.
# TODO(pcc): remove this when we're ready to add these checks by default.
# TODO( Reassess the validity of the next expression.
use_cfi_icall = (target_os == "linux" || is_chromeos_lacros) &&
target_cpu == "x64" && is_official_build
# Print detailed diagnostics when Control Flow Integrity detects a violation.
use_cfi_diag = false
# Let Control Flow Integrity continue execution instead of crashing when
# printing diagnostics (use_cfi_diag = true).
use_cfi_recover = false
# Compile for fuzzing with LLVM LibFuzzer.
# See
use_libfuzzer = false
# Compile for fuzzing with AFL.
use_afl = false
# Compile for fuzzing with an external engine (e.g., Grammarinator).
use_external_fuzzing_engine = false
# Enables core ubsan security features. Will later be removed once it matches
# is_ubsan.
is_ubsan_security = false
# Helper variable for testing builds with disabled libfuzzer.
# Not for client use.
disable_libfuzzer = false
# Optimize for coverage guided fuzzing (balance between speed and number of
# branches). Can be also used to remove non-determinism and other issues.
optimize_for_fuzzing = false
# Value for -fsanitize-coverage flag. Setting this causes
# use_sanitizer_coverage to be enabled.
# This flag is not used for libFuzzer (use_libfuzzer=true). Instead, we use:
# -fsanitize=fuzzer-no-link
# Default value when unset and use_fuzzing_engine=true:
# trace-pc-guard
# Default value when unset and use_sanitizer_coverage=true:
# trace-pc-guard,indirect-calls
sanitizer_coverage_flags = ""
# When enabled, only relevant sanitizer defines are set, but compilation
# happens with no extra flags. This is useful when in component build
# enabling sanitizers only in some of the components.
use_sanitizer_configs_without_instrumentation = false
# When true, seed corpora archives are built.
archive_seed_corpus = true
declare_args() {
# Enable checks for bad casts: derived cast and unrelated cast.
# TODO(krasin): remove this, when we're ready to add these checks by default.
use_cfi_cast = is_cfi && (is_chromeos_ash || is_chromeos_lacros)
# Compile for Undefined Behaviour Sanitizer's vptr checks.
is_ubsan_vptr = is_ubsan_security
# Disable sanitizers for non-target toolchains.
if (!is_a_target_toolchain) {
is_asan = false
is_cfi = false
is_hwasan = false
is_lsan = false
is_msan = false
is_tsan = false
is_ubsan = false
is_ubsan_null = false
is_ubsan_no_recover = false
is_ubsan_security = false
is_ubsan_vptr = false
msan_track_origins = 0
sanitizer_coverage_flags = ""
use_afl = false
use_cfi_diag = false
use_cfi_recover = false
use_libfuzzer = false
use_locally_built_instrumented_libraries = false
use_sanitizer_coverage = false
# Use dynamic libraries instrumented by one of the sanitizers instead of the
# standard system libraries. We have instrumented system libraries for msan,
# which requires them to prevent false positives.
# TODO(thakis): Maybe remove this variable.
use_prebuilt_instrumented_libraries = is_msan
# Whether we are doing a fuzzer build. Normally this should be checked instead
# of checking "use_libfuzzer || use_afl" because often developers forget to
# check for "use_afl".
use_fuzzing_engine = use_libfuzzer || use_afl || use_external_fuzzing_engine
# Args that are in turn dependent on other args must be in a separate
# declare_args block. User overrides are only applied at the end of a
# declare_args block.
declare_args() {
# Generates an owners file for each fuzzer test.
# TODO( Remove this arg when finding OWNERS is faster.
generate_fuzzer_owners = use_fuzzing_engine
use_sanitizer_coverage =
!use_clang_coverage &&
(use_fuzzing_engine || sanitizer_coverage_flags != "")
# Code coverage works inside the sandbox via the
# help of several helper IPCs. Unfortunately, the sandbox-only path does not
# work well for fuzzing builds. Since fuzzing builds already disable the
# sandbox when dumping coverage, limit the sandbox-only path to non-fuzzing
# builds.
# Everything is IPC on Fuchsia, so this workaround for code coverage inside
# the sandbox does not apply.
use_clang_profiling_inside_sandbox =
use_clang_profiling && !use_fuzzing_engine && !is_fuchsia
if (use_fuzzing_engine && sanitizer_coverage_flags == "") {
sanitizer_coverage_flags = "trace-pc-guard"
} else if (use_sanitizer_coverage && sanitizer_coverage_flags == "") {
sanitizer_coverage_flags = "trace-pc-guard,indirect-calls"
# Whether we are linking against a sanitizer runtime library. Among other
# things, this changes the default symbol level and other settings in order to
# prepare to create stack traces "live" using the sanitizer runtime.
using_sanitizer = is_asan || is_hwasan || is_lsan || is_tsan || is_msan ||
is_ubsan || is_ubsan_null || is_ubsan_vptr ||
is_ubsan_security || use_sanitizer_coverage || use_cfi_diag
assert(!using_sanitizer || is_clang,
"Sanitizers (is_*san) require setting is_clang = true in 'gn args'")
assert(!is_cfi || is_clang,
"is_cfi requires setting is_clang = true in 'gn args'")
prebuilt_instrumented_libraries_available =
is_msan && (msan_track_origins == 0 || msan_track_origins == 2)
if (use_libfuzzer && (is_linux || is_chromeos)) {
if (is_asan) {
# We do leak checking with libFuzzer on Linux. Set is_lsan for code that
# relies on LEAK_SANITIZER define to avoid false positives.
is_lsan = true
# MSan only links Chrome properly in release builds (brettw -- 9/1/2015). The
# same is possibly true for the other non-ASan sanitizers. But regardless of
# whether it links, one would normally never run a sanitizer in debug mode.
# Running in debug mode probably indicates you forgot to set the "is_debug =
# false" flag in the build args. ASan seems to run fine in debug mode.
# If you find a use-case where you want to compile a sanitizer in debug mode
# and have verified it works, ask brettw and we can consider removing it from
# this condition. We may also be able to find another way to enable your case
# without having people accidentally get broken builds by compiling an
# unsupported or unadvisable configurations.
# For one-off testing, just comment this assertion out.
assert(!is_debug || !(is_msan || is_ubsan || is_ubsan_null || is_ubsan_vptr),
"Sanitizers should generally be used in release (set is_debug=false).")
assert(!is_hwasan || (is_android && current_cpu == "arm64"),
"HWASan only supported on Android ARM64 builds.")
assert(!is_msan || ((is_linux || is_chromeos) && current_cpu == "x64"),
"MSan currently only works on 64-bit Linux and ChromeOS builds.")
assert(!is_lsan || is_asan, "is_lsan = true requires is_asan = true also.")
# ASAN build on Windows is not working in debug mode. Intercepting memory
# allocation functions is hard on Windows and not yet implemented in LLVM.
assert(!is_win || !is_debug || !is_asan,
"ASan on Windows doesn't work in debug (set is_debug=false).")
# libFuzzer targets can fail to build or behave incorrectly when built without
# ASAN on Windows.
assert(!is_win || !use_libfuzzer || is_asan,
"use_libfuzzer on Windows requires setting is_asan = true")
# Make sure that if we recover on detection (i.e. not crash), diagnostics are
# printed.
assert(!use_cfi_recover || use_cfi_diag,
"Only use CFI recovery together with diagnostics.")
# TODO( the use_sanitizer_coverage arg is currently
# not supported by the Chromium mac_clang_x64 toolchain on iOS distribution.
# The coverage works with iOS toolchain but it is broken when the mac
# toolchain is used as a secondary one on iOS distribution. E.g., it should be
# possible to build the "net" target for iOS with the sanitizer coverage
# enabled.
!(use_sanitizer_coverage && is_mac && target_os == "ios"),
" use_sanitizer_coverage=true is not supported by the " +
"Chromium mac_clang_x64 toolchain on iOS distribution. Please set " +
"the argument value to false.")
# Use these lists of configs to disable instrumenting code that is part of a
# fuzzer, but which isn't being targeted (such as libprotobuf-mutator, *
# and libprotobuf when they are built as part of a proto fuzzer). Adding or
# removing these lists does not have any effect if use_libfuzzer or use_afl are
# not passed as arguments to gn.
not_fuzzed_remove_configs = []
not_fuzzed_remove_nonasan_configs = []
if (use_fuzzing_engine) {
# Removing coverage should always just work.
not_fuzzed_remove_configs += [ "//build/config/coverage:default_coverage" ]
not_fuzzed_remove_nonasan_configs +=
[ "//build/config/coverage:default_coverage" ]
if (!is_msan) {
# Allow sanitizer instrumentation to be removed if we are not using MSan
# since binaries cannot be partially instrumented with MSan.
not_fuzzed_remove_configs +=
[ "//build/config/sanitizers:default_sanitizer_flags" ]
# Certain parts of binaries must be instrumented with ASan if the rest of
# the binary is. For these, only remove non-ASan sanitizer instrumentation.
if (!is_asan) {
not_fuzzed_remove_nonasan_configs +=
[ "//build/config/sanitizers:default_sanitizer_flags" ]
assert(not_fuzzed_remove_nonasan_configs == not_fuzzed_remove_configs)