path: root/build/config/compiler/BUILD.gn

# Copyright (c) 2013 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.

import("//build/config/android/config.gni")
import("//build/config/chrome_build.gni")
import("//build/config/compiler/compiler.gni")
import("//build/config/nacl/config.gni")
import("//build/toolchain/cc_wrapper.gni")

if (current_cpu == "arm") {
  import("//build/config/arm.gni")
}
if (current_cpu == "mipsel" || current_cpu == "mips64el") {
  import("//build/config/mips.gni")
}
if (is_win) {
  import("//build/config/win/visual_studio_version.gni")
}

declare_args() {
  # Default to warnings as errors for default workflow, where we catch
  # warnings with known toolchains. Allow overriding this e.g. for Chromium
  # builds on Linux that could use a different version of the compiler.
  # With GCC, warnings in no-Chromium code are always not treated as errors.
  treat_warnings_as_errors = true

  # Normally, Android builds are lightly optimized, even for debug builds, to
  # keep binary size down. Setting this flag to true disables such optimization
  android_full_debug = false

  # Whether to use the binary binutils checked into third_party/binutils.
  # These are not multi-arch so cannot be used except on x86 and x86-64 (the
  # only two architectures that are currently checked in). Turn this off when
  # you are using a custom toolchain and need to control -B in cflags.
  linux_use_bundled_binutils = is_linux && current_cpu == "x64"
  binutils_path = rebase_path("//third_party/binutils/Linux_x64/Release/bin",
                              root_build_dir)

  # Compile in such a way as to make it possible for the profiler to unwind full
  # stack frames. Setting this flag has a large effect on the performance of the
  # generated code than just setting profiling, but gives the profiler more
  # information to analyze.
  # Requires profiling to be set to true.
  enable_full_stack_frames_for_profiling = false

  # TODO(GYP): We should be using 64-bit gold for linking on both 64-bit Linux
  # and 32-bit linux; 32-bit Gold runs out of address-space on 32-bit builds.
  # However, something isn't quite working right on the 32-bit builds.
  use_gold = is_linux && (current_cpu == "x64" || current_cpu == "arm")

  # When we are going to use gold we need to find it.
  # This is initialized below, after use_gold might have been overridden.
  gold_path = false

  # use_debug_fission: whether to use split DWARF debug info
  # files. This can reduce link time significantly, but is incompatible
  # with some utilities such as icecc and ccache. Requires gold and
  # gcc >= 4.8 or clang.
  # http://gcc.gnu.org/wiki/DebugFission
  #
  # This is a placeholder value indicating that the code below should set
  # the default.  This is necessary to delay the evaluation of the default
  # value expression until after its input values such as use_gold have
  # been set, e.g. by a toolchain_args() block.
  use_debug_fission = "default"

  if (is_win) {
    # Whether the VS xtree header has been patched to disable warning 4702. If
    # it has, then we don't need to disable 4702 (unreachable code warning).
    # The patch is preapplied to the internal toolchain and hence all bots.
    msvs_xtree_patched = false
  }

  # Omit unwind support in official builds to save space.
  # We can use breakpad for these builds.
  exclude_unwind_tables = is_chrome_branded && is_official_build
}

# Apply the default logic for these values if they were not set explicitly.
if (gold_path == false) {
  if (use_gold) {
    gold_path = rebase_path("//third_party/binutils/Linux_x64/Release/bin",
                            root_build_dir)
  } else {
    gold_path = ""
  }
}

if (use_debug_fission == "default") {
  use_debug_fission = is_debug && !is_win && use_gold &&
                      linux_use_bundled_binutils && cc_wrapper == ""
}

# default_include_dirs ---------------------------------------------------------
#
# This is a separate config so that third_party code (which would not use the
# source root and might have conflicting versions of some headers) can remove
# this and specify their own include paths.
config("default_include_dirs") {
  include_dirs = [
    "//",
    root_gen_dir,
  ]
}

# compiler ---------------------------------------------------------------------
#
# Base compiler configuration.
#
# See also "runtime_library" below for related stuff and a discussion about
# where stuff should go. Put warning related stuff in the "warnings" config.

config("compiler") {
  asmflags = []
  cflags = []
  cflags_c = []
  cflags_cc = []
  cflags_objc = []
  cflags_objcc = []
  ldflags = []
  defines = []
  configs = []

  # System-specific flags. If your compiler flags apply to one of the
  # categories here, add it to the associated file to keep this shared config
  # smaller.
  if (is_win) {
    configs += [ "//build/config/win:compiler" ]
  } else if (is_android) {
    configs += [ "//build/config/android:compiler" ]
  } else if (is_linux) {
    configs += [ "//build/config/linux:compiler" ]
  } else if (is_nacl) {
    configs += [ "//build/config/nacl:compiler" ]
  } else if (is_ios || is_mac) {
    configs += [ "//build/config/mac:compiler" ]
  }

  # See the definitions below.
  configs += [
    ":compiler_cpu_abi",
    ":compiler_codegen",
  ]

  if (is_win) {
    ldflags += [
      # Suggested by Microsoft Devrel to avoid
      #   LINK : fatal error LNK1248: image size (80000000) exceeds maximum allowable size (80000000)
      # which started happening more regularly after VS2013 Update 4.
      # Needs to be a bit lower for VS2015, or else errors out.
      "/maxilksize:0x7ff00000",

      # Tell the linker to crash on failures.
      "/fastfail",
    ]
  }

  # In general, Windows is totally different, but all the other builds share
  # some common GCC configuration.
  if (!is_win) {
    # Common GCC compiler flags setup.
    # --------------------------------
    cflags += [ "-fno-strict-aliasing" ]  # See http://crbug.com/32204
    cflags_cc += [
      # If this is removed then remove the corresponding /Zc:threadSafeInit- for
      # Windows.
      "-fno-threadsafe-statics",

      # Not exporting C++ inline functions can generally be applied anywhere
      # so we do so here. Normal function visibility is controlled by
      # //build/config/gcc:symbol_visibility_hidden.
      "-fvisibility-inlines-hidden",
    ]

    # Stack protection.
    if (is_mac) {
      cflags += [ "-fstack-protector-all" ]
    } else if (is_posix && !is_chromeos && !is_nacl) {
      # TODO(phajdan.jr): Use -fstack-protector-strong when our gcc supports it.
      cflags += [ "--param=ssp-buffer-size=4" ]

      # The x86 toolchain currently has problems with stack-protector.
      if (is_android && current_cpu == "x86") {
        cflags += [ "-fno-stack-protector" ]
      } else {
        cflags += [ "-fstack-protector" ]
      }
    }

    # Linker warnings.
    if (!(is_chromeos && current_cpu == "arm") &&
        !(is_android && use_order_profiling) && !is_mac && !is_ios) {
      # TODO(jochen): Enable this on chromeos on arm. http://crbug.com/356580
      # TODO(lizeb,pasko): Fix link errors when linking with order_profiling=1
      # crbug.com/485542
      ldflags += [ "-Wl,--fatal-warnings" ]
    }
  }

  if (is_clang && is_debug) {
    # Allow comparing the address of references and 'this' against 0
    # in debug builds. Technically, these can never be null in
    # well-defined C/C++ and Clang can optimize such checks away in
    # release builds, but they may be used in asserts in debug builds.
    cflags_cc += [
      "-Wno-undefined-bool-conversion",
      "-Wno-tautological-undefined-compare",
    ]
  }

  if (is_clang && !is_nacl) {
    # This is here so that all files get recompiled after a clang roll and
    # when turning clang on or off. (defines are passed via the command line,
    # and build system rebuild things when their commandline changes). Nothing
    # should ever read this define.
    defines +=
        [ "CR_CLANG_REVISION=" + exec_script("//tools/clang/scripts/update.py",
                                             [ "--print-revision" ],
                                             "trim string") ]
  }

  # Non-Mac Posix compiler flags setup.
  # -----------------------------------
  if (is_posix && !(is_mac || is_ios)) {
    if (enable_profiling && !is_debug) {
      cflags += [
        "-fno-omit-frame-pointer",
        "-g",
      ]

      if (enable_full_stack_frames_for_profiling) {
        cflags += [
          "-fno-inline",
          "-fno-optimize-sibling-calls",
        ]
      }
    }

    defines += [ "_FILE_OFFSET_BITS=64" ]

    if (!is_android) {
      defines += [
        "_LARGEFILE_SOURCE",
        "_LARGEFILE64_SOURCE",
      ]
    }

    if (!is_nacl) {
      if (exclude_unwind_tables) {
        cflags += [
          "-fno-unwind-tables",
          "-fno-asynchronous-unwind-tables",
        ]
        defines += [ "NO_UNWIND_TABLES" ]
      } else {
        cflags += [ "-funwind-tables" ]
      }
    }
  }

  # Linux/Android common flags setup.
  # ---------------------------------
  if (is_linux || is_android) {
    cflags += [
      "-fPIC",
      "-pipe",  # Use pipes for communicating between sub-processes. Faster.
    ]

    ldflags += [
      "-fPIC",
      "-Wl,-z,noexecstack",
      "-Wl,-z,now",
      "-Wl,-z,relro",
    ]
    if (!using_sanitizer && !use_cfi_diag) {
      ldflags += [ "-Wl,-z,defs" ]
    }
  }

  # Linux-specific compiler flags setup.
  # ------------------------------------
  if (use_gold) {
    ldflags += [
      "-B$gold_path",

      # Newer gccs and clangs support -fuse-ld, use the flag to force gold
      # selection.
      # gcc -- http://gcc.gnu.org/onlinedocs/gcc-4.8.0/gcc/Optimize-Options.html
      "-fuse-ld=gold",

      # Experimentation found that using four linking threads
      # saved ~20% of link time.
      # https://groups.google.com/a/chromium.org/group/chromium-dev/browse_thread/thread/281527606915bb36
      # Only apply this to the target linker, since the host
      # linker might not be gold, but isn't used much anyway.
      # TODO(raymes): Disable threading because gold is frequently
      # crashing on the bots: crbug.com/161942.
      #"-Wl,--threads",
      #"-Wl,--thread-count=4",
    ]

    if (!using_sanitizer && !(is_android && use_order_profiling)) {
      # TODO(brettw) common.gypi has this only for target toolset.
      ldflags += [ "-Wl,--icf=all" ]
    }

    # TODO(thestig): Make this flag work with GN.
    #if (!is_official_build && !is_chromeos && !(is_asan || is_lsan || is_tsan || is_msan)) {
    #  ldflags += [
    #    "-Wl,--detect-odr-violations",
    #  ]
    #}
  } else if (linux_use_bundled_binutils) {
    # Gold is the default linker for the bundled binutils so we explicitly
    # enable the bfd linker when use_gold is not set.
    ldflags += [ "-fuse-ld=bfd" ]
  }

  if (linux_use_bundled_binutils) {
    cflags += [ "-B$binutils_path" ]
  }

  # Clang-specific compiler flags setup.
  # ------------------------------------
  if (is_clang) {
    cflags += [ "-fcolor-diagnostics" ]
  }

  # Makes builds independent of absolute file path.
  # clang-cl (used if is_win) doesn't expose this flag.
  # Currently disabled for nacl since its toolchain lacks this flag (too old).
  # TODO(zforman): Once nacl's toolchain is updated, remove check.
  if (is_clang && !is_win && !is_nacl) {
    absolute_path = rebase_path("//.")
    cflags += [ "-fdebug-prefix-map=$absolute_path=." ]
  }

  # C++11 compiler flags setup.
  # ---------------------------
  if (is_linux || is_android || (is_nacl && is_clang)) {
    # gnu++11 instead of c++11 is needed because some code uses typeof() (a
    # GNU extension).
    # TODO(thakis): Eventually switch this to c++11 instead,
    # http://crbug.com/427584
    cflags_cc += [ "-std=gnu++11" ]
  } else if (!is_win && !is_nacl) {
    # TODO(mcgrathr) - the NaCl GCC toolchain doesn't support either gnu++11
    # or c++11; we technically don't need this toolchain any more, but there
    # are still a few buildbots using it, so until those are turned off
    # we need the !is_nacl clause and the (is_nacl && is_clang) clause, above.
    cflags_cc += [ "-std=c++11" ]
  }

  if (is_mac) {
    # Tell the compiler to use libc++'s headers and the linker to link
    # against libc++.  The latter part normally requires OS X 10.7,
    # but we still support running on 10.6.  How does this work?  Two
    # parts:
    # 1. Chromium's clang doesn't error on -mmacosx-version-min=10.6
    #    combined with -stdlib=libc++ (it normally silently produced a
    #    binary that doesn't run on 10.6)
    # 2. Further down, library_dirs is set to
    #    third_party/libc++-static, which contains a static
    #    libc++.a library.  The linker then links against that instead
    #    of against /usr/lib/libc++.dylib when it sees the -lc++ flag
    #    added by the driver.
    #
    # In component builds, just link to the system libc++.  This has
    # the effect of making everything depend on libc++, which means
    # component-build binaries won't run on 10.6 (no libc++ there),
    # but for a developer-only configuration that's ok.  (We don't
    # want to raise the deployment target yet so that official and
    # dev builds have the same deployment target.  This affects
    # things like which functions are considered deprecated.)
    cflags_cc += [ "-stdlib=libc++" ]
    ldflags += [ "-stdlib=libc++" ]
    if (!is_component_build && !is_asan) {
      ldflags += [
        "-L",
        rebase_path("//third_party/libc++-static", root_build_dir),
      ]
    }
  }

  # Pass the same C/C++ flags to the objective C/C++ compiler.
  cflags_objc += cflags_c
  cflags_objcc += cflags_cc

  # Assign any flags set for the C compiler to asmflags so that they are sent
  # to the assembler. The Windows assembler takes different types of flags
  # so only do so for posix platforms.
  if (is_posix) {
    asmflags += cflags
    asmflags += cflags_c
  }
}

# This provides the basic options to select the target CPU and ABI.
# It is factored out of "compiler" so that special cases can use this
# without using everything that "compiler" brings in.  Options that
# tweak code generation for a particular CPU do not belong here!
# See "compiler_codegen", below.
config("compiler_cpu_abi") {
  cflags = []
  ldflags = []

  if (is_posix && !(is_mac || is_ios)) {
    # CPU architecture. We may or may not be doing a cross compile now, so for
    # simplicity we always explicitly set the architecture.
    if (current_cpu == "x64") {
      cflags += [
        "-m64",
        "-march=x86-64",
      ]
      ldflags += [ "-m64" ]
    } else if (current_cpu == "x86") {
      cflags += [ "-m32" ]
      ldflags += [ "-m32" ]
    } else if (current_cpu == "arm") {
      if (is_clang && !is_android && !is_nacl) {
        cflags += [
          "-target",
          "arm-linux-gnueabihf",
        ]
        ldflags += [
          "-target",
          "arm-linux-gnueabihf",
        ]
      }
      if (!is_nacl) {
        cflags += [
          "-march=$arm_arch",
          "-mfloat-abi=$arm_float_abi",
        ]
        if (arm_use_thumb) {
          cflags += [ "-mthumb" ]
          if (is_android && !is_clang) {
            # Clang doesn't support this option.
            cflags += [ "-mthumb-interwork" ]
          }
        }
      }
      if (arm_tune != "") {
        cflags += [ "-mtune=$arm_tune" ]
      }
    } else if (current_cpu == "mipsel") {
      if (mips_arch_variant == "r6") {
        if (is_clang) {
          cflags += [
            "-target",
            "mipsel-linux-gnu",
            "-march=mips32r6",
          ]
          ldflags += [
            "-target",
            "mipsel-linux-gnu",
          ]
        } else {
          cflags += [
            "-mips32r6",
            "-Wa,-mips32r6",
          ]
          if (is_android) {
            ldflags += [
              "-mips32r6",
              "-Wl,-melf32ltsmip",
            ]
          }
        }
      } else if (mips_arch_variant == "r2") {
        if (is_clang) {
          if (is_android) {
            cflags += [
              "-target",
              "mipsel-linux-android",
              "-march=mipsel",
              "-mcpu=mips32r2",
            ]
            ldflags += [
              "-target",
              "mipsel-linux-android",
            ]
          } else {
            cflags += [
              "-target",
              "mipsel-linux-gnu",
              "-march=mipsel",
              "-mcpu=mips32r2",
            ]
            ldflags += [
              "-target",
              "mipsel-linux-gnu",
            ]
          }
        } else {
          cflags += [
            "-mips32r2",
            "-Wa,-mips32r2",
          ]
          if (mips_float_abi == "hard" && mips_fpu_mode != "") {
            cflags += [ "-m$mips_fpu_mode" ]
          }
        }
      } else if (mips_arch_variant == "r1") {
        if (is_clang) {
          if (is_android) {
            cflags += [
              "-target",
              "mipsel-linux-android",
              "-march=mipsel",
              "-mcpu=mips32",
            ]
            ldflags += [
              "-target",
              "mipsel-linux-android",
            ]
          } else {
            cflags += [
              "-target",
              "mipsel-linux-gnu",
              "-march=mipsel",
              "-mcpu=mips32",
            ]
            ldflags += [
              "-target",
              "mipsel-linux-gnu",
            ]
          }
        } else {
          cflags += [
            "-mips32",
            "-Wa,-mips32",
          ]
        }
      }

      if (mips_dsp_rev == 1) {
        cflags += [ "-mdsp" ]
      } else if (mips_dsp_rev == 2) {
        cflags += [ "-mdspr2" ]
      }

      cflags += [ "-m${mips_float_abi}-float" ]
    } else if (current_cpu == "mips64el") {
      if (mips_arch_variant == "r6") {
        cflags += [
          "-mips64r6",
          "-Wa,-mips64r6",
        ]
        ldflags += [ "-mips64r6" ]
      } else if (mips_arch_variant == "r2") {
        cflags += [
          "-mips64r2",
          "-Wa,-mips64r2",
        ]
        ldflags += [ "-mips64r2" ]
      }
    } else if (current_cpu == "pnacl" && is_nacl_nonsfi) {
      if (target_cpu == "x86" || target_cpu == "x64") {
        cflags += [
          "-arch",
          "x86-32-nonsfi",
          "--pnacl-bias=x86-32-nonsfi",
          "--target=i686-unknown-nacl",
        ]
        ldflags += [
          "-arch",
          "x86-32-nonsfi",
          "--target=i686-unknown-nacl",
        ]
      } else if (target_cpu == "arm") {
        cflags += [
          "-arch",
          "arm-nonsfi",
          "--pnacl-bias=arm-nonsfi",
          "--target=armv7-unknown-nacl-gnueabihf",
        ]
        ldflags += [
          "-arch",
          "arm-nonsfi",
          "--target=armv7-unknown-nacl-gnueabihf",
        ]
      }
    }
  }

  asmflags = cflags
}

# This provides options to tweak code generation that are necessary
# for particular Chromium code or for working around particular
# compiler bugs (or the combination of the two).
config("compiler_codegen") {
  configs = []
  cflags = []

  if (is_nacl) {
    configs += [ "//build/config/nacl:compiler_codegen" ]
  } else if (is_posix && !is_mac && !is_ios) {
    if (current_cpu == "x86") {
      if (is_clang) {
        cflags += [
          # Else building libyuv gives clang's register allocator issues,
          # see llvm.org/PR15798 / crbug.com/233709
          "-momit-leaf-frame-pointer",
        ]
      }
    } else if (current_cpu == "arm") {
      if (is_android && !is_clang) {
        # Clang doesn't support these flags.
        cflags += [
          # The tree-sra optimization (scalar replacement for
          # aggregates enabling subsequent optimizations) leads to
          # invalid code generation when using the Android NDK's
          # compiler (r5-r7). This can be verified using
          # webkit_unit_tests' WTF.Checked_int8_t test.
          "-fno-tree-sra",

          # The following option is disabled to improve binary
          # size and performance in gcc 4.9.
          "-fno-caller-saves",
        ]
      }
    }
  }

  asmflags = cflags
}

# This is separate from :compiler_codegen (and not even a sub-config there)
# so that some targets can remove it from the list with:
#   configs -= [ "//build/config/compiler:clang_stackrealign" ]
# See https://crbug.com/556393 for details of where it must be avoided.
config("clang_stackrealign") {
  if (is_clang && current_cpu == "x86" && is_linux) {
    cflags = [
      # Align the stack on 16-byte boundaries, http://crbug.com/418554.
      "-mstack-alignment=16",
      "-mstackrealign",
    ]
  }
}

config("compiler_arm_fpu") {
  if (current_cpu == "arm" && !is_ios && !is_nacl) {
    cflags = [ "-mfpu=$arm_fpu" ]
    asmflags = cflags
  }
}

# runtime_library -------------------------------------------------------------
#
# Sets the runtime library and associated options.
#
# How do you determine what should go in here vs. "compiler" above? Consider if
# a target might choose to use a different runtime library (ignore for a moment
# if this is possible or reasonable on your system). If such a target would want
# to change or remove your option, put it in the runtime_library config. If a
# target wants the option regardless, put it in the compiler config.

config("runtime_library") {
  defines = []
  configs = []

  # System-specific flags. If your compiler flags apply to one of the
  # categories here, add it to the associated file to keep this shared config
  # smaller.
  if (is_win) {
    configs += [ "//build/config/win:runtime_library" ]
  } else if (is_linux) {
    configs += [ "//build/config/linux:runtime_library" ]
  } else if (is_ios) {
    configs += [ "//build/config/ios:runtime_library" ]
  } else if (is_mac) {
    configs += [ "//build/config/mac:runtime_library" ]
  } else if (is_android) {
    configs += [ "//build/config/android:runtime_library" ]
  }

  if (is_posix) {
    configs += [ "//build/config/posix:runtime_library" ]
  }

  if (is_component_build) {
    defines += [ "COMPONENT_BUILD" ]
  }
}

# default_warnings ------------------------------------------------------------
#
# Collects all warning flags that are used by default.  This is used as a
# subconfig of both chromium_code and no_chromium_code.  This way these
# flags are guaranteed to appear on the compile command line after -Wall.
config("default_warnings") {
  cflags = []
  cflags_cc = []

  if (is_win) {
    if (treat_warnings_as_errors) {
      cflags += [ "/WX" ]
    }

    cflags += [
      # Warnings permanently disabled:

      # C4091: 'typedef ': ignored on left of 'X' when no variable is
      #                    declared.
      # This happens in a number of Windows headers. Dumb.
      "/wd4091",

      # C4127: conditional expression is constant
      # This warning can in theory catch dead code and other problems, but
      # triggers in far too many desirable cases where the conditional
      # expression is either set by macros or corresponds some legitimate
      # compile-time constant expression (due to constant template args,
      # conditionals comparing the sizes of different types, etc.).  Some of
      # these can be worked around, but it's not worth it.
      "/wd4127",

      # C4251: 'identifier' : class 'type' needs to have dll-interface to be
      #        used by clients of class 'type2'
      # This is necessary for the shared library build.
      "/wd4251",

      # C4351: new behavior: elements of array 'array' will be default
      #        initialized
      # This is a silly "warning" that basically just alerts you that the
      # compiler is going to actually follow the language spec like it's
      # supposed to, instead of not following it like old buggy versions did.
      # There's absolutely no reason to turn this on.
      "/wd4351",

      # C4355: 'this': used in base member initializer list
      # It's commonly useful to pass |this| to objects in a class' initializer
      # list.  While this warning can catch real bugs, most of the time the
      # constructors in question don't attempt to call methods on the passed-in
      # pointer (until later), and annotating every legit usage of this is
      # simply more hassle than the warning is worth.
      "/wd4355",

      # C4503: 'identifier': decorated name length exceeded, name was
      #        truncated
      # This only means that some long error messages might have truncated
      # identifiers in the presence of lots of templates.  It has no effect on
      # program correctness and there's no real reason to waste time trying to
      # prevent it.
      "/wd4503",

      # Warning C4589 says: "Constructor of abstract class ignores
      # initializer for virtual base class." Disable this warning because it
      # is flaky in VS 2015 RTM. It triggers on compiler generated
      # copy-constructors in some cases.
      "/wd4589",

      # C4611: interaction between 'function' and C++ object destruction is
      #        non-portable
      # This warning is unavoidable when using e.g. setjmp/longjmp.  MSDN
      # suggests using exceptions instead of setjmp/longjmp for C++, but
      # Chromium code compiles without exception support.  We therefore have to
      # use setjmp/longjmp for e.g. JPEG decode error handling, which means we
      # have to turn off this warning (and be careful about how object
      # destruction happens in such cases).
      "/wd4611",

      # Warnings to evaluate and possibly fix/reenable later:

      "/wd4100",  # Unreferenced formal function parameter.
      "/wd4121",  # Alignment of a member was sensitive to packing.
      "/wd4244",  # Conversion: possible loss of data.
      "/wd4505",  # Unreferenced local function has been removed.
      "/wd4510",  # Default constructor could not be generated.
      "/wd4512",  # Assignment operator could not be generated.
      "/wd4610",  # Class can never be instantiated, constructor required.
      "/wd4838",  # Narrowing conversion. Doesn't seem to be very useful.
      "/wd4995",  # 'X': name was marked as #pragma deprecated
      "/wd4996",  # Deprecated function warning.

      # These are variable shadowing warnings that are new in VS2015. We
      # should work through these at some point -- they may be removed from
      # the RTM release in the /W4 set.
      "/wd4456",
      "/wd4457",
      "/wd4458",
      "/wd4459",
    ]

    if (visual_studio_version == "2015") {
      cflags += [
        # VC++ 2015 changes 32-bit size_t truncation warnings from 4244 to 4267.
        # Example: short TruncTest(size_t x) { return x; }
        # Since we disable 4244 we need to disable 4267 during migration.
        # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
        "/wd4267",

        # C4312 is a VS 2015 64-bit warning for integer to larger pointer.
        # TODO(brucedawson): fix warnings, crbug.com/554200
        "/wd4312",

        # TODO(brucedawson): http://crbug.com/593448 4334 is a 'suspicious
        # shift' warning and 4595 is an 'illegal inline operator new' warning
        # Both are new in VS 2015 Update 2 and can safely be deferred for now.
        "/wd4334",
        "/wd4595",
      ]
    }

    # VS xtree header file needs to be patched or 4702 (unreachable code
    # warning) is reported if _HAS_EXCEPTIONS=0. Disable the warning if xtree is
    # not patched.
    if (!msvs_xtree_patched &&
        exec_script("../../win_is_xtree_patched.py", [], "value") == 0) {
      cflags += [ "/wd4702" ]  # Unreachable code.
    }

    # Building with Clang on Windows is a work in progress and very
    # experimental. See crbug.com/82385.
    # Keep this in sync with the similar block in build/common.gypi
    if (is_clang) {
      cflags += [
        # TODO(hans): Make this list shorter eventually, http://crbug.com/504657
        "-Qunused-arguments",  # http://crbug.com/504658
        "-Wno-microsoft-enum-value",  # http://crbug.com/505296
        "-Wno-unknown-pragmas",  # http://crbug.com/505314
        "-Wno-microsoft-cast",  # http://crbug.com/550065
      ]
    }
  } else {
    if (is_mac && !is_nacl) {
      # When compiling Objective-C, warns if a method is used whose
      # availability is newer than the deployment target. This is not
      # required when compiling Chrome for iOS.
      cflags += [ "-Wpartial-availability" ]
    }

    # Suppress warnings about ABI changes on ARM (Clang doesn't give this
    # warning).
    if (current_cpu == "arm" && !is_clang) {
      cflags += [ "-Wno-psabi" ]
    }

    if (!is_clang) {
      cflags_cc += [
        # See comment for -Wno-c++11-narrowing.
        "-Wno-narrowing",
      ]

      # Don't warn about the "typedef 'foo' locally defined but not used"
      # for gcc 4.8.
      # TODO: remove this flag once all builds work. See crbug.com/227506
      cflags += [ "-Wno-unused-local-typedefs" ]
    }
  }

  # Common Clang and GCC warning setup.
  if (!is_win || is_clang) {
    cflags += [
      # Disables.
      "-Wno-missing-field-initializers",  # "struct foo f = {0};"
      "-Wno-unused-parameter",  # Unused function parameters.
    ]
  }

  if (is_chromeos) {
    # TODO(thakis): Remove, http://crbug.com/263960
    if (is_clang) {
      cflags_cc += [ "-Wno-reserved-user-defined-literal" ]
    } else {
      cflags_cc += [ "-Wno-literal-suffix" ]
    }
  }

  if (is_clang) {
    cflags += [
      # TODO(thakis): Consider -Wloop-analysis (turns on
      # -Wrange-loop-analysis too).

      # This warns on using ints as initializers for floats in
      # initializer lists (e.g. |int a = f(); CGSize s = { a, a };|),
      # which happens in several places in chrome code. Not sure if
      # this is worth fixing.
      "-Wno-c++11-narrowing",

      # Warns on switches on enums that cover all enum values but
      # also contain a default: branch. Chrome is full of that.
      "-Wno-covered-switch-default",

      # Clang considers the `register` keyword as deprecated, but e.g.
      # code generated by flex (used in angle) contains that keyword.
      # http://crbug.com/255186
      "-Wno-deprecated-register",

      # TODO(thakis): This used to be implied by -Wno-unused-function,
      # which we no longer use. Check if it makes sense to remove
      # this as well. http://crbug.com/316352
      "-Wno-unneeded-internal-declaration",

      # TODO(hans): Get this cleaned up, http://crbug.com/428099
      "-Wno-inconsistent-missing-override",
    ]

    # NaCl's Clang compiler and Chrome's hermetic Clang compiler will almost
    # always have different versions. Certain flags may not be recognized by
    # one version or the other.
    if (!is_nacl) {
      # Flags NaCl (Clang 3.7) does not recognize.
      cflags += [
        # TODO(thakis): Enable this, crbug.com/507717
        "-Wno-shift-negative-value",
      ]
    }
  }
}

# chromium_code ---------------------------------------------------------------
#
# Toggles between higher and lower warnings for code that is (or isn't)
# part of Chromium.

config("chromium_code") {
  if (is_win) {
    cflags = [ "/W4" ]  # Warning level 4.
  } else {
    cflags = [ "-Wall" ]
    if (treat_warnings_as_errors) {
      cflags += [ "-Werror" ]
    }
    if (is_clang) {
      # Enable -Wextra for chromium_code when we control the compiler.
      cflags += [ "-Wextra" ]
    }

    # In Chromium code, we define __STDC_foo_MACROS in order to get the
    # C99 macros on Mac and Linux.
    defines = [
      "__STDC_CONSTANT_MACROS",
      "__STDC_FORMAT_MACROS",
    ]

    if (!is_debug && !using_sanitizer &&
        (!is_linux || !is_clang || is_official_build)) {
      # _FORTIFY_SOURCE isn't really supported by Clang now, see
      # http://llvm.org/bugs/show_bug.cgi?id=16821.
      # It seems to work fine with Ubuntu 12 headers though, so use it in
      # official builds.
      #
      # Non-chromium code is not guaranteed to compile cleanly with
      # _FORTIFY_SOURCE. Also, fortified build may fail when optimizations are
      # disabled, so only do that for Release build.
      defines += [ "_FORTIFY_SOURCE=2" ]
    }
  }

  configs = [ ":default_warnings" ]
}

config("no_chromium_code") {
  cflags = []
  cflags_cc = []
  defines = []

  if (is_win) {
    cflags += [
      "/W3",  # Warning level 3.
      "/wd4800",  # Disable warning when forcing value to bool.
      "/wd4267",  # TODO(jschuh): size_t to int.
      "/wd4996",  # Deprecated function warning.
    ]
    defines += [
      "_CRT_NONSTDC_NO_WARNINGS",
      "_CRT_NONSTDC_NO_DEPRECATE",
    ]
  } else {
    # GCC may emit unsuppressible warnings so don't add -Werror for no chromium
    # code. crbug.com/589724
    if (treat_warnings_as_errors && is_clang) {
      cflags += [ "-Werror" ]
    }
    if (is_clang && !is_nacl) {
      # TODO(thakis): Remove !is_nacl once
      # https://codereview.webrtc.org/1552863002/ made its way into chromium.
      cflags += [ "-Wall" ]
    }
  }

  if (is_clang) {
    cflags += [
      # Lots of third-party libraries have unused variables. Instead of
      # suppressing them individually, we just blanket suppress them here.
      "-Wno-unused-variable",
    ]
  }

  if (is_linux || is_android) {
    cflags_cc += [
      # Don't warn about hash_map in third-party code.
      "-Wno-deprecated",
    ]
  }

  configs = [ ":default_warnings" ]
}

# rtti ------------------------------------------------------------------------
#
# Allows turning Run-Time Type Identification on or off.

config("rtti") {
  if (is_win) {
    cflags_cc = [ "/GR" ]
  }
}
config("no_rtti") {
  # CFI diagnostics and UBsan vptr require RTTI.
  if (!use_cfi_diag && !is_ubsan_vptr) {
    if (is_win) {
      cflags_cc = [ "/GR-" ]
    } else {
      cflags_cc = [ "-fno-rtti" ]
      cflags_objcc = cflags_cc
    }
  }
}

# Warnings ---------------------------------------------------------------------

# This will generate warnings when using Clang if code generates exit-time
# destructors, which will slow down closing the program.
# TODO(thakis): Make this a blacklist instead, http://crbug.com/101600
config("wexit_time_destructors") {
  # TODO: Enable on Windows too, http://crbug.com/404525
  if (is_clang && !is_win) {
    cflags = [ "-Wexit-time-destructors" ]
  }
}

# On Windows compiling on x64, VC will issue a warning when converting
# size_t to int because it will truncate the value. Our code should not have
# these warnings and one should use a static_cast or a checked_cast for the
# conversion depending on the case. However, a lot of code still needs to be
# fixed. Apply this config to such targets to disable the warning.
#
# Note that this can be applied regardless of platform and architecture to
# clean up the call sites. This will only apply the flag when necessary.
#
# TODO(jschuh): crbug.com/167187 fix this and delete this config.
config("no_size_t_to_int_warning") {
  if (is_win && current_cpu == "x64") {
    cflags = [ "/wd4267" ]
  }
}

# Some code presumes that pointers to structures/objects are compatible
# regardless of whether what they point to is already known to be valid.
# gcc 4.9 and earlier had no way of suppressing this warning without
# supressing the rest of them.  Here we centralize the identification of
# the gcc 4.9 toolchains.
config("no_incompatible_pointer_warnings") {
  cflags = []
  if (is_clang) {
    cflags += [ "-Wno-incompatible-pointer-types" ]
  } else if (current_cpu == "mipsel") {
    cflags += [ "-w" ]
  } else if (is_chromeos && current_cpu == "arm") {
    cflags += [ "-w" ]
  }
}

# Optimization -----------------------------------------------------------------
#
# The BUILDCONFIG file sets the "default_optimization" config on targets by
# default. It will be equivalent to either "optimize" (release) or
# "no_optimize" (debug) optimization configs.
#
# You can override the optimization level on a per-target basis by removing the
# default config and then adding the named one you want:
#
#   configs -= [ "//build/config/compiler:default_optimization" ]
#   configs += [ "//build/config/compiler:optimize_max" ]

# Shared settings for both "optimize" and "optimize_max" configs.
# IMPORTANT: On Windows "/O1" and "/O2" must go before the common flags.
if (is_win) {
  common_optimize_on_cflags = [
    "/Ob2",  # Both explicit and auto inlining.
    "/Oy-",  # Disable omitting frame pointers, must be after /O2.
    "/d2Zi+",  # Improve debugging of optimized code.
    "/Zc:inline",  # Remove unreferenced COMDAT (faster links).
  ]
  if (!is_asan) {
    common_optimize_on_cflags += [
      # Put data in separate COMDATs. This allows the linker
      # to put bit-identical constants at the same address even if
      # they're unrelated constants, which saves binary size.
      # This optimization can't be used when ASan is enabled because
      # it is not compatible with the ASan ODR checker.
      "/Gw",
    ]
  }
  common_optimize_on_ldflags = [ "/OPT:ICF" ]  # Redundant COMDAT folding.
  if (is_official_build) {
    common_optimize_on_ldflags += [
      "/OPT:REF",  # Remove unreferenced data.
      "/LTCG",  # Link-time code generation.

      # Set the number of LTCG code-gen threads to eight. The default is four.
      # This gives a 5-10% link speedup.
      "/cgthreads:8",
    ]
  }
} else {
  common_optimize_on_cflags = [
    # Don't emit the GCC version ident directives, they just end up in the
    # .comment section taking up binary size.
    "-fno-ident",

    # Put data and code in their own sections, so that unused symbols
    # can be removed at link time with --gc-sections.
    "-fdata-sections",
    "-ffunction-sections",
  ]
  common_optimize_on_ldflags = []

  if (is_android) {
    # We don't omit frame pointers on arm64 since they are required
    # to correctly unwind stackframes which contain system library
    # function frames (crbug.com/391706).
    if (!using_sanitizer && target_cpu != "arm64") {
      common_optimize_on_cflags += [ "-fomit-frame-pointer" ]
    }

    # TODO(jdduke) Re-enable on mips after resolving linking
    # issues with libc++ (crbug.com/456380).
    if (current_cpu != "mipsel" && current_cpu != "mips64el") {
      common_optimize_on_ldflags += [
        # Warn in case of text relocations.
        "-Wl,--warn-shared-textrel",
      ]
    }
  }

  if (is_mac || is_ios) {
    if (symbol_level == 2) {
      # Mac dead code stripping requires symbols.
      common_optimize_on_ldflags += [ "-Wl,-dead_strip" ]
    }
  } else {
    # Non-Mac Posix linker flags.
    common_optimize_on_ldflags += [
      # Specifically tell the linker to perform optimizations.
      # See http://lwn.net/Articles/192624/ .
      "-Wl,-O1",
      "-Wl,--gc-sections",
    ]

    if (!using_sanitizer) {
      # Functions interposed by the sanitizers can make ld think
      # that some libraries aren't needed when they actually are,
      # http://crbug.com/234010. As workaround, disable --as-needed.
      common_optimize_on_ldflags += [ "-Wl,--as-needed" ]
    }
  }
}

# Default "optimization on" config.
config("optimize") {
  if (is_win) {
    # Favor size over speed, /O1 must be before the common flags. The GYP
    # build also specifies /Os and /GF but these are implied by /O1.
    cflags = [ "/O1" ] + common_optimize_on_cflags + [ "/Oi" ]
  } else if (is_android || is_ios) {
    # Favor size over speed.
    cflags = [ "-Os" ] + common_optimize_on_cflags
  } else {
    # Linux & Mac favor speed over size.
    # TODO(brettw) it's weird that Mac and desktop Linux are different. We should
    # explore favoring size over speed in this case as well.
    cflags = [ "-O2" ] + common_optimize_on_cflags
  }
  ldflags = common_optimize_on_ldflags
}

# Turn off optimizations.
config("no_optimize") {
  if (is_win) {
    cflags = [
      "/Od",  # Disable optimization.
      "/Ob0",  # Disable all inlining (on by default).
    ]
  } else if (is_android && !android_full_debug) {
    # On Android we kind of optimize some things that don't affect debugging
    # much even when optimization is disabled to get the binary size down.
    cflags = [
      "-Os",
      "-fdata-sections",
      "-ffunction-sections",
    ]

    # We don't omit frame pointers on arm64 since they are required
    # to correctly unwind stackframes which contain system library
    # function frames (crbug.com/391706).
    if (!using_sanitizer && target_cpu != "arm64") {
      cflags += [ "-fomit-frame-pointer" ]
    }

    # Don't use gc-sections since it can cause links to succeed when they
    # actually shouldn't. http://crbug.com/159847
    ldflags = common_optimize_on_ldflags - [ "-Wl,--gc-sections" ]
  } else {
    cflags = [ "-O0" ]
    ldflags = []
  }
}

# Turns up the optimization level. On Windows, this implies whole program
# optimization and link-time code generation which is very expensive and should
# be used sparingly.
config("optimize_max") {
  if (is_nacl_irt) {
    # The NaCl IRT is a special case and always wants its own config.
    # Various components do:
    #   if (!is_debug) {
    #     configs -= [ "//build/config/compiler:default_optimization" ]
    #     configs += [ "//build/config/compiler:optimize_max" ]
    #   }
    # So this config has to have the selection logic just like
    # "default_optimization", below.
    configs = [ "//build/config/nacl:irt_optimize" ]
  } else {
    ldflags = common_optimize_on_ldflags
    if (is_win) {
      # Favor speed over size, /O2 must be before the common flags. The GYP
      # build also specifies /Ot, /Oi, and /GF, but these are implied by /O2.
      cflags = [ "/O2" ] + common_optimize_on_cflags
      if (is_official_build) {
        # TODO(GYP): TODO(dpranke): Should these only be on in an official
        # build, or on all the time? For now we'll require official build so
        # that the compile is clean.
        cflags += [
          "/GL",  # Whole program optimization.

          # Disable Warning 4702 ("Unreachable code") for the WPO/PGO builds.
          # Probably anything that this would catch that wouldn't be caught in a
          # normal build isn't going to actually be a bug, so the incremental
          # value of C4702 for PGO builds is likely very small.
          "/wd4702",
        ]
      }
    } else {
      cflags = [ "-O2" ] + common_optimize_on_cflags
    }
  }
}

# The default optimization applied to all targets. This will be equivalent to
# either "optimize" or "no_optimize", depending on the build flags.
config("default_optimization") {
  if (is_nacl_irt) {
    # The NaCl IRT is a special case and always wants its own config.
    # It gets optimized the same way regardless of the type of build.
    configs = [ "//build/config/nacl:irt_optimize" ]
  } else if (is_debug) {
    configs = [ ":no_optimize" ]
  } else {
    configs = [ ":optimize" ]
  }
}

# Symbols ----------------------------------------------------------------------

# The BUILDCONFIG file sets the "default_symbols" config on targets by
# default. It will be equivalent to one the three specific symbol levels.
#
# You can override the symbol level on a per-target basis by removing the
# default config and then adding the named one you want:
#
#   configs -= [ "//build/config/compiler:default_symbols" ]
#   configs += [ "//build/config/compiler:symbols" ]

# Full symbols.
config("symbols") {
  if (is_win) {
    import("//build/toolchain/goma.gni")
    if (use_goma) {
      cflags = [ "/Z7" ]  # No PDB file
    } else {
      cflags = [ "/Zi" ]  # Produce PDB file, no edit and continue.
    }
    if (is_win_fastlink && visual_studio_version != "2013") {
      # Tell VS 2015+ to create a PDB that references debug
      # information in .obj and .lib files instead of copying
      # it all. This flag is incompatible with /PROFILE
      ldflags = [ "/DEBUG:FASTLINK" ]
    } else {
      ldflags = [ "/DEBUG" ]
    }
  } else {
    cflags = [ "-g2" ]
    if (use_debug_fission) {
      cflags += [ "-gsplit-dwarf" ]
    }
    asmflags = cflags
    ldflags = []
  }
}

# Minimal symbols.
config("minimal_symbols") {
  if (is_win) {
    # Linker symbols for backtraces only.
    cflags = []
    if (is_win_fastlink && visual_studio_version != "2013") {
      # Tell VS 2015+ to create a PDB that references debug
      # information in .obj and .lib files instead of copying
      # it all. This flag is incompatible with /PROFILE
      ldflags = [ "/DEBUG:FASTLINK" ]
    } else {
      ldflags = [ "/DEBUG" ]
    }
  } else {
    cflags = [ "-g1" ]
    if (use_debug_fission) {
      cflags += [ "-gsplit-dwarf" ]
    }
    asmflags = cflags
    ldflags = []
  }
}

# No symbols.
config("no_symbols") {
  if (!is_win) {
    cflags = [ "-g0" ]
    asmflags = cflags
  }
}

# Default symbols.
config("default_symbols") {
  if (symbol_level == 0) {
    configs = [ ":no_symbols" ]
  } else if (symbol_level == 1) {
    configs = [ ":minimal_symbols" ]
  } else if (symbol_level == 2) {
    configs = [ ":symbols" ]
  } else {
    assert(false)
  }
}

if (is_ios || is_mac) {
  # On Mac and iOS, this enables support for ARC (automatic ref-counting).
  # See http://clang.llvm.org/docs/AutomaticReferenceCounting.html.
  config("enable_arc") {
    common_flags = [ "-fobjc-arc" ]
    cflags_objc = common_flags
    cflags_objcc = common_flags
  }
}