build/config/gcc/BUILD.gn

# Copyright 2014 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.

# This config causes functions not to be automatically exported from shared
# libraries. By default, all symbols are exported but this means there are
# lots of exports that slow everything down. In general we explicitly mark
# which functiosn we want to export from components.
#
# Some third_party code assumes all functions are exported so this is separated
# into its own config so such libraries can remove this config to make symbols
# public again.
#
# See http://gcc.gnu.org/wiki/Visibility
config("symbol_visibility_hidden") {
  # Note that -fvisibility-inlines-hidden is set globally in the compiler
  # config since that can almost always be applied.
  cflags = [ "-fvisibility=hidden" ]
}

# Settings for executables and shared libraries.
config("executable_ldconfig") {
  if (is_android) {
    ldflags = [
      "-Bdynamic",
      "-Wl,-z,nocopyreloc",
    ]
  } else {
    # Android doesn't support rpath.
    ldflags = [
      # Want to pass "\$". GN will re-escape as required for ninja.
      "-Wl,-rpath=\$ORIGIN/",
      "-Wl,-rpath-link=",
      "-Wl,-z,origin",

      # Newer binutils don't set DT_RPATH unless you disable "new" dtags
      # and the new DT_RUNPATH doesn't work without --no-as-needed flag.
      "-Wl,--disable-new-dtags",
    ]
  }
}

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

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 //, but there isn't a better
  # option to keep all source file name references uniformly relative to
  # a single root.
  absolute_path = rebase_path("//.")
  relative_path = rebase_path("//.", root_build_dir)
  cflags = [
    # This makes sure that the DW_AT_comp_dir string (the current
    # directory while running the compiler, which is the basis for all
    # relative source file names in the DWARF info) is represented as
    # relative to //.
    "-fdebug-prefix-map=$absolute_path=$relative_path",

    # 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
    # (//buildtools/...), 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",
  ]
}