1# Copyright 2014 The Chromium Authors. All rights reserved. 2# Use of this source code is governed by a BSD-style license that can be 3# found in the LICENSE file. 4 5import("//build/config/sanitizers/sanitizers.gni") 6import("//build/toolchain/toolchain.gni") 7 8# This config causes functions not to be automatically exported from shared 9# libraries. By default, all symbols are exported but this means there are 10# lots of exports that slow everything down. In general we explicitly mark 11# which functiosn we want to export from components. 12# 13# Some third_party code assumes all functions are exported so this is separated 14# into its own config so such libraries can remove this config to make symbols 15# public again. 16# 17# See http://gcc.gnu.org/wiki/Visibility 18config("symbol_visibility_hidden") { 19 # Note that -fvisibility-inlines-hidden is set globally in the compiler 20 # config since that can almost always be applied. 21 cflags = [ "-fvisibility=hidden" ] 22} 23 24# This config is usually set when :symbol_visibility_hidden is removed. 25# It's often a good idea to set visibility explicitly, as there're flags 26# which would error out otherwise (e.g. -fsanitize=cfi-unrelated-cast) 27config("symbol_visibility_default") { 28 cflags = [ "-fvisibility=default" ] 29} 30 31# The rpath is the dynamic library search path. Setting this config on a link 32# step will put the directory where the build generates shared libraries into 33# the rpath. 34# 35# It's important that this *not* be used for release builds we push out. 36# Chrome uses some setuid binaries, and hard links preserve setuid bits. An 37# unprivileged user could gain root privileges by hardlinking a setuid 38# executable and then adding in whatever binaries they want to run into the lib 39# directory. 40# 41# Example bug: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=520126 42# 43# This is required for component builds since the build generates many shared 44# libraries in the build directory that we expect to be automatically loaded. 45# It will be automatically applied in this case by :executable_ldconfig. 46# 47# In non-component builds, certain test binaries may expect to load dynamic 48# libraries from the current directory. As long as these aren't distributed, 49# this is OK. For these cases use something like this: 50# 51# if (is_linux && !is_component_build) { 52# configs += [ "//build/config/gcc:rpath_for_built_shared_libraries" ] 53# } 54config("rpath_for_built_shared_libraries") { 55 if (!is_android) { 56 # Note: Android doesn't support rpath. 57 if (shlib_subdir != ".") { 58 rpath_link = "${shlib_subdir}/" 59 } else { 60 rpath_link = "." 61 } 62 ldflags = [ 63 # Want to pass "\$". GN will re-escape as required for ninja. 64 "-Wl,-rpath=\$ORIGIN/${rpath_link}", 65 "-Wl,-rpath-link=${rpath_link}", 66 ] 67 } 68} 69 70# Settings for executables. 71config("executable_ldconfig") { 72 if (is_android) { 73 ldflags = [ 74 "-Bdynamic", 75 "-Wl,-z,nocopyreloc", 76 ] 77 } else { 78 # See the rpath_for... config above for why this is necessary for component 79 # builds. Sanitizers use a custom libc++ where this is also necessary. 80 if (is_component_build || using_sanitizer) { 81 configs = [ ":rpath_for_built_shared_libraries" ] 82 } 83 84 # Find the path containing shared libraries for this toolchain 85 # relative to the build directory. ${root_out_dir} will be a 86 # subdirectory of ${root_build_dir} when cross compiling. 87 rebased_out_dir = rebase_path(root_out_dir, root_build_dir) 88 if (shlib_subdir != ".") { 89 rpath_link = "${rebased_out_dir}/${shlib_subdir}" 90 } else { 91 rpath_link = rebased_out_dir 92 } 93 94 ldflags = [ 95 "-Wl,-rpath-link=${rpath_link}", 96 97 # TODO(GYP): Do we need a check on the binutils version here? 98 # 99 # Newer binutils don't set DT_RPATH unless you disable "new" dtags 100 # and the new DT_RUNPATH doesn't work without --no-as-needed flag. 101 "-Wl,--disable-new-dtags", 102 ] 103 if (current_cpu == "mipsel") { 104 ldflags += [ "-pie" ] 105 } 106 } 107} 108 109config("no_exceptions") { 110 cflags_cc = [ "-fno-exceptions" ] 111 cflags_objcc = cflags_cc 112} 113