Beginning work on GN build

build/config/sanitizers/sanitizers.gni

+# 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 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 vptr checks.
+  is_ubsan_vptr = 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 download prebuilt binaries from
+  # GCS.
+  use_prebuilt_instrumented_libraries = false
+
+  # Enable building with SyzyAsan which can find certain types of memory
+  # errors. Only works on Windows. See
+  # https://github.com/google/syzygy/wiki/SyzyASanHowTo
+  is_syzyasan = false
+
+  # Compile with Control Flow Integrity to protect virtual calls and casts.
+  # See http://clang.llvm.org/docs/ControlFlowIntegrity.html
+  #
+  # TODO(pcc): Remove this flag if/when CFI is enabled in official builds.
+  is_cfi = false
+
+  # By default, Control Flow Integrity will crash the program if it detects a
+  # violation. Set this to true to print detailed diagnostics instead.
+  use_cfi_diag = false
+
+  # Compile for fuzzing with LLVM LibFuzzer.
+  # See http://www.chromium.org/developers/testing/libfuzzer
+  use_libfuzzer = false
+
+  # Enables core ubsan security features. Will later be removed once it matches
+  # is_ubsan.
+  is_ubsan_security = false
+
+  # Compile for fuzzing with Dr. Fuzz
+  # See http://www.chromium.org/developers/testing/dr-fuzz
+  use_drfuzz = false
+
+  # Helper variable for testing builds with disabled libfuzzer.
+  # Not for client use.
+  disable_libfuzzer = false
+
+  # Value for -fsanitize-coverage flag. Setting this causes
+  # use_sanitizer_coverage to be enabled.
+  # Default value when unset and use_sanitizer_coverage=true:
+  #     edge,indirect-calls,8bit-counters
+  sanitizer_coverage_flags = ""
+}
+
+# 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() {
+  # Use libc++ (buildtools/third_party/libc++ and
+  # buildtools/third_party/libc++abi) instead of stdlibc++ as standard library.
+  # This is intended to be used for instrumented builds.
+  use_custom_libcxx = (is_asan && is_linux && !is_chromeos) || is_tsan ||
+                      is_msan || is_ubsan || is_ubsan_security || use_libfuzzer
+
+  # Enable -fsanitize-coverage.
+  use_sanitizer_coverage = use_libfuzzer || sanitizer_coverage_flags != ""
+}
+
+if (use_sanitizer_coverage && sanitizer_coverage_flags == "") {
+  sanitizer_coverage_flags = "edge,indirect-calls,8bit-counters"
+}
+
+using_sanitizer = is_asan || is_lsan || is_tsan || is_msan || is_ubsan ||
+                  is_ubsan_vptr || is_ubsan_security
+
+assert(!using_sanitizer || is_clang,
+       "Sanitizers (is_*san) require setting is_clang = true in 'gn args'")
+
+# 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_lsan || is_tsan || is_ubsan || is_ubsan_vptr),
+    "Sanitizers should generally be used in release (set is_debug=false).")