build/config/BUILD.gn

# Copyright 2016 The Fuchsia 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/compiler.gni")
import("//build/toolchain/goma.gni")

declare_args() {
  # Clang crash reports directory path. Use empty path to disable altogether.
  crash_diagnostics_dir = "$root_build_dir/clang-crashreports"

  if (is_fuchsia) {
    # Controls whether the compiler emits full stack frames for function calls.
    # This reduces performance but increases the ability to generate good
    # stack traces, especially when we have bugs around unwind table generation.
    # It applies only for Fuchsia targets (see below where it is unset).
    #
    # TODO(ZX-2361): Theoretically unwind tables should be good enough so we can
    # remove this option when the issues are addressed.
    enable_frame_pointers = is_debug
  }
}

# No frame pointers for host compiles.
if (!is_fuchsia) {
  enable_frame_pointers = false
}

config("compiler") {
  asmflags = []
  cflags = [ "-fcolor-diagnostics" ]
  cflags_c = []
  cflags_cc = [ "-fvisibility-inlines-hidden" ]
  cflags_objc = []
  cflags_objcc = [ "-fvisibility-inlines-hidden" ]
  ldflags = []
  defines = []
  configs = []

  if (current_os == "fuchsia") {
    configs += [ "//build/config/fuchsia:compiler" ]
  } else {
    cflags_c += [ "-std=c11" ]
    cflags_cc += [
      "-std=c++17",
      "-stdlib=libc++",
    ]
    if (current_os == "linux") {
      configs += [ "//build/config/linux:compiler" ]
    } else if (current_os == "mac") {
      configs += [ "//build/config/mac:compiler" ]
    }
  }

  # Linker on macOS does not support `color-diagnostics`
  if (current_os != "mac") {
    ldflags += [ "-Wl,--color-diagnostics" ]
  }

  if (crash_diagnostics_dir != "") {
    cflags += [ "-fcrash-diagnostics-dir=" +
                rebase_path(crash_diagnostics_dir, root_build_dir) ]
  }

  asmflags += cflags
  asmflags += cflags_c
}

config("relative_paths") {
  # Make builds independent of absolute file path.  The file names
  # embedded in debugging information will be expressed as relative to
  # the build directory, e.g. "../.." for an "out/subdir" under //.
  #
  # This is consistent with the file names in __FILE__ expansions
  # (e.g. in assertion messages), which the compiler doesn't provide a
  # way to remap.  That way source file names in logging and
  # symbolization can all be treated the same way.  This won't go well
  # if $root_build_dir is not a subdirectory of //, but there isn't
  # a better option to keep all source file name references uniformly
  # relative to a single root. Stripping out per-user or per-config
  # path information additionally allows caching compilers (like Goma)
  # to reuse compilation results amongst users/configs.
  #
  # Given a build directory of of the form
  # "/xxx/yyy/fuchsia/out/my-config-name", we want to normalize as
  # follows:
  #
  #    /xxx/yyy/fuchsia/out/my-config-name         → .
  #    /xxx/yyy/fuchsia/out/my-config-name.zircon  → ../my-config-name.zircon
  #    /xxx/yyy/fuchsia/out                        → ..
  #    /xxx/yyy/fuchsia/src                        → ../src
  #
  # GCC and Clang only perform naïve prefix matching, so we need to
  # match replace multiple prefixes
  # ("/xxx/yyy/fuchsia/out/my-config-name", "/xxx/yyy/fuchsia/out",
  # "/xxx/yyy/fuchsia") to avoid excess path information leaking into
  # the debug symbols.

  if (use_goma) {
    # TODO(TC-585): `-fdebug-prefix-map` is also used by Goma to canonicalize
    # build commands, allowing it to reuse compilation results for users running
    # out of different working directories. However, it only supports a single
    # "-fdebug-prefix-map" prefix. Attempting to provide more than one causes
    # canonicalization to fail, meaning that builds running out of different
    # directories won't share cache results. For now, we just provide a single
    # debug-prefix-map, even though more would be ideal.

    # Map "/some/dir/fuchsia" to "../..".
    cflags = [ "-fdebug-prefix-map=" + rebase_path("//") + "=" +
               rebase_path("//", root_build_dir) ]
  } else {
    cflags = [
      # Map "/some/dir/fuchsia/out/my-build.my-arch" to ".".
      "-fdebug-prefix-map=" + rebase_path(root_build_dir) + "=.",

      # Map "/some/dir/fuchsia/out" to "..".
      "-fdebug-prefix-map=" + rebase_path("$root_build_dir/..") + "=..",

      # Map "/some/dir/fuchsia" to "../..".
      "-fdebug-prefix-map=" + rebase_path("//.") + "=" +
          rebase_path("//.", root_build_dir),
    ]
  }

  cflags += [
    # This makes sure that include directories in the toolchain are
    # represented as relative to the build directory (because that's how
    # we invoke the compiler), rather than absolute.  This can affect
    # __FILE__ expansions (e.g. assertions in system headers).  We
    # normally run a compiler that's someplace within the source tree
    # (//prebuilt/...), so its absolute installation path will have a
    # prefix matching absolute_path and hence be mapped to relative_path
    # in the debugging information, so this should actually be
    # superfluous for purposes of the debugging information.
    "-no-canonical-prefixes",
  ]
}

config("debug") {
  cflags = [ "-O0" ]
  ldflags = cflags
}

config("release") {
  defines = [ "NDEBUG=1" ]
  cflags = [
    "-O3",
    "-fdata-sections",
    "-ffunction-sections",
  ]
  ldflags = cflags
  if (current_os == "mac") {
    ldflags += [ "-Wl,-dead_strip" ]
  } else {
    ldflags += [ "-Wl,--gc-sections" ]
  }
}

config("exceptions") {
  cflags_cc = [ "-fexceptions" ]
  cflags_objcc = cflags_cc
}

config("no_exceptions") {
  cflags_cc = [ "-fno-exceptions" ]
  cflags_objcc = cflags_cc
}

config("rtti") {
  cflags_cc = [ "-frtti" ]
  cflags_objcc = cflags_cc
}

config("no_rtti") {
  cflags_cc = [ "-fno-rtti" ]
  cflags_objcc = cflags_cc
}

config("default_include_dirs") {
  include_dirs = [
    "//",
    root_gen_dir,
  ]
}

config("minimal_symbols") {
  cflags = [ "-gline-tables-only" ]
  asmflags = cflags
  ldflags = cflags
}

config("symbols") {
  cflags = [ "-g3" ]
  asmflags = cflags
  ldflags = cflags
}

config("no_symbols") {
  cflags = [ "-g0" ]
  asmflags = cflags
  ldflags = 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(symbol_level >= 0 && symbol_level <= 2)
  }
}

config("default_frame_pointers") {
  if (enable_frame_pointers) {
    configs = [ ":frame_pointers" ]
  } else {
    configs = [ ":no_frame_pointers" ]
  }
}

config("frame_pointers") {
  cflags = [ "-fno-omit-frame-pointer" ]
}

config("no_frame_pointers") {
  cflags = [ "-fomit-frame-pointer" ]
}

config("default_warnings") {
  cflags = [
    "-Wall",
    "-Wextra",
    "-Wnewline-eof",
    "-Wno-unused-parameter",

    # TODO(TC-620): disable -Wimplicit-int-float-conversion which has been
    # introduced in https://reviews.llvm.org/D64666 until our source is clean.
    "-Wno-unknown-warning-option",
    "-Wno-implicit-int-float-conversion",

    # TODO(34837): disable -Wdangling until we clear all instances.
    "-Wno-dangling",
  ]
}

config("symbol_visibility_hidden") {
  # Disable libc++ visibility annotations to make sure that the compiler option
  # has effect on symbols defined in libc++ headers. Note that we don't want to
  # disable these annotations altogether to ensure that our toolchain is usable
  # outside of our build since not every user uses hidden visibility by default.
  defines = [ "_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS" ]
  cflags = [ "-fvisibility=hidden" ]
}

config("symbol_no_undefined") {
  if (current_os == "mac") {
    ldflags = [ "-Wl,-undefined,error" ]
  } else {
    ldflags = [ "-Wl,--no-undefined" ]
  }
}

config("shared_library_config") {
  configs = []
  cflags = []

  if (current_os == "fuchsia") {
    configs += [ "//build/config/fuchsia:shared_library_config" ]
  } else if (current_os == "linux") {
    cflags += [ "-fPIC" ]
  } else if (current_os == "mac") {
    configs += [ "//build/config/mac:mac_dynamic_flags" ]
  }
}

config("executable_config") {
  configs = []

  if (current_os == "fuchsia") {
    configs += [
      "//build/config/fuchsia:executable_config",
      "//build/config/fuchsia:fdio_config",
    ]
  } else if (current_os == "mac") {
    configs += [
      "//build/config/mac:mac_dynamic_flags",
      "//build/config/mac:mac_executable_flags",
    ]
  }
}

config("default_libs") {
  configs = []

  if (current_os == "mac") {
    configs += [ "//build/config/mac:default_libs" ]
  }
}