Force builds to use C++17 in standalone builds.
The C++ Style Guide [1] currently recommends C++17, but Chromium is
using C++20 for the most part. [2] Change standalone PDFium to use its
own BUILDCONFIG.gn, which overrides the C++ standard config to always
use C++17. This allows PDFium to roll DEPS for //build and get all the
benefits, without surprises to the C++ standard config.
Note that this does not control the build config when PDFium is
embedded in another project.
[1] https://google.github.io/styleguide/cppguide.html#C++_Version
[2] https://crbug.com/1284275
Bug: pdfium:1932
Change-Id: I6b56a392a2b8837504540d48155cb3797afc2df5
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/101970
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: K. Moon <kmoon@chromium.org>
diff --git a/.gn b/.gn
index 9d6330b..b2bf99d 100644
--- a/.gn
+++ b/.gn
@@ -2,7 +2,9 @@
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
-buildconfig = "//build/config/BUILDCONFIG.gn"
+# TODO(crbug.com/pdfium/1932): Switch back to //build/config/BUILDCONFIG.gn if
+# appropriate.
+buildconfig = "//build_overrides/BUILDCONFIG.gn"
# The python interpreter to use by default. On Windows, this will look
# for python3.exe and python3.bat.
diff --git a/build_overrides/BUILDCONFIG.gn b/build_overrides/BUILDCONFIG.gn
new file mode 100644
index 0000000..768fe60
--- /dev/null
+++ b/build_overrides/BUILDCONFIG.gn
@@ -0,0 +1,620 @@
+# Copyright 2022 The PDFium Authors
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# =============================================================================
+# WHAT IS THIS FILE?
+# =============================================================================
+#
+# This is a copy of //build/config/BUILDCONFIG.gn. The difference is it adds an
+# extra default_compiler_configs to use PDFium's desired default compiler
+# config. See "PDFIUM MODIFICATIONS" below.
+#
+# This is the main GN build configuration. This file is loaded after the
+# build args (args.gn) for the build directory and after the toplevel ".gn"
+# file (which points to this file as the build configuration).
+#
+# This file will be executed and the resulting context will be used to execute
+# every other file in the build. So variables declared here (that don't start
+# with an underscore) will be implicitly global.
+
+# =============================================================================
+# PLATFORM SELECTION
+# =============================================================================
+#
+# There are two main things to set: "os" and "cpu". The "toolchain" is the name
+# of the GN thing that encodes combinations of these things.
+#
+# Users typically only set the variables "target_os" and "target_cpu" in "gn
+# args", the rest are set up by our build and internal to GN.
+#
+# There are three different types of each of these things: The "host"
+# represents the computer doing the compile and never changes. The "target"
+# represents the main thing we're trying to build. The "current" represents
+# which configuration is currently being defined, which can be either the
+# host, the target, or something completely different (like nacl). GN will
+# run the same build file multiple times for the different required
+# configuration in the same build.
+#
+# This gives the following variables:
+# - host_os, host_cpu, host_toolchain
+# - target_os, target_cpu, default_toolchain
+# - current_os, current_cpu, current_toolchain.
+#
+# Note the default_toolchain isn't symmetrical (you would expect
+# target_toolchain). This is because the "default" toolchain is a GN built-in
+# concept, and "target" is something our build sets up that's symmetrical with
+# its GYP counterpart. Potentially the built-in default_toolchain variable
+# could be renamed in the future.
+#
+# When writing build files, to do something only for the host:
+# if (current_toolchain == host_toolchain) { ...
+
+if (target_os == "") {
+ target_os = host_os
+}
+
+if (target_cpu == "") {
+ if (target_os == "android") {
+ # If we're building for Android, we should assume that we want to
+ # build for ARM by default, not the host_cpu (which is likely x64).
+ # This allows us to not have to specify both target_os and target_cpu
+ # on the command line.
+ target_cpu = "arm"
+ } else {
+ target_cpu = host_cpu
+ }
+}
+
+if (current_cpu == "") {
+ current_cpu = target_cpu
+}
+if (current_os == "") {
+ current_os = target_os
+}
+
+# =============================================================================
+# BUILD FLAGS
+# =============================================================================
+#
+# This block lists input arguments to the build, along with their default
+# values.
+#
+# If a value is specified on the command line, it will overwrite the defaults
+# given in a declare_args block, otherwise the default will be used.
+#
+# YOU SHOULD ALMOST NEVER NEED TO ADD FLAGS TO THIS FILE. GN allows any file in
+# the build to declare build flags. If you need a flag for a single component,
+# you can just declare it in the corresponding BUILD.gn file.
+#
+# - If your feature is a single target, say //components/foo, you can put
+# a declare_args() block in //components/foo/BUILD.gn and use it there.
+# Nobody else in the build needs to see the flag.
+#
+# - Defines based on build variables should be implemented via the generated
+# build flag header system. See //build/buildflag_header.gni. You can put
+# the buildflag_header target in the same file as the build flag itself. You
+# should almost never set "defines" directly.
+#
+# - If your flag toggles a target on and off or toggles between different
+# versions of similar things, write a "group" target that forwards to the
+# right target (or no target) depending on the value of the build flag. This
+# group can be in the same BUILD.gn file as the build flag, and targets can
+# depend unconditionally on the group rather than duplicating flag checks
+# across many targets.
+#
+# - If a semi-random set of build files REALLY needs to know about a define and
+# the above pattern for isolating the build logic in a forwarding group
+# doesn't work, you can put the argument in a .gni file. This should be put
+# in the lowest level of the build that knows about this feature (which should
+# almost always be outside of the //build directory!).
+#
+# Other flag advice:
+#
+# - Use boolean values when possible. If you need a default value that expands
+# to some complex thing in the default case (like the location of the
+# compiler which would be computed by a script), use a default value of -1 or
+# the empty string. Outside of the declare_args block, conditionally expand
+# the default value as necessary.
+#
+# - Use a name like "use_foo" or "is_foo" (whatever is more appropriate for
+# your feature) rather than just "foo".
+#
+# - Write good comments directly above the declaration with no blank line.
+# These comments will appear as documentation in "gn args --list".
+#
+# - Don't call exec_script inside declare_args. This will execute the script
+# even if the value is overridden, which is wasteful. See first bullet.
+
+declare_args() {
+ # Set to enable the official build level of optimization. This has nothing
+ # to do with branding, but enables an additional level of optimization above
+ # release (!is_debug). This might be better expressed as a tri-state
+ # (debug, release, official) but for historical reasons there are two
+ # separate flags.
+ #
+ # IMPORTANT NOTE: (!is_debug) is *not* sufficient to get satisfying
+ # performance. In particular, DCHECK()s are still enabled for release builds,
+ # which can halve overall performance, and do increase memory usage. Always
+ # set "is_official_build" to true for any build intended to ship to end-users.
+ is_official_build = false
+
+ # Set to true when compiling with the Clang compiler.
+ is_clang = current_os != "linux" ||
+ (current_cpu != "s390x" && current_cpu != "s390" &&
+ current_cpu != "ppc64" && current_cpu != "ppc" &&
+ current_cpu != "mips" && current_cpu != "mips64" &&
+ current_cpu != "riscv64")
+
+ # Allows the path to a custom target toolchain to be injected as a single
+ # argument, and set as the default toolchain.
+ custom_toolchain = ""
+
+ # This should not normally be set as a build argument. It's here so that
+ # every toolchain can pass through the "global" value via toolchain_args().
+ host_toolchain = ""
+
+ # Do not set this directly.
+ # It should be set only by //build/toolchains/android:robolectric_x64.
+ # True when compiling native code for use with robolectric_binary().
+ is_robolectric = false
+
+ # DON'T ADD MORE FLAGS HERE. Read the comment above.
+}
+
+declare_args() {
+ # Debug build. Enabling official builds automatically sets is_debug to false.
+ is_debug = !is_official_build
+}
+
+declare_args() {
+ # Component build. Setting to true compiles targets declared as "components"
+ # as shared libraries loaded dynamically. This speeds up development time.
+ # When false, components will be linked statically.
+ #
+ # For more information see
+ # https://chromium.googlesource.com/chromium/src/+/main/docs/component_build.md
+ is_component_build = is_debug && current_os != "ios"
+}
+
+assert(!(is_debug && is_official_build), "Can't do official debug builds")
+assert(!(current_os == "ios" && is_component_build),
+ "Can't use component build on iOS")
+
+# ==============================================================================
+# TOOLCHAIN SETUP
+# ==============================================================================
+#
+# Here we set the default toolchain, as well as the variable host_toolchain
+# which will identify the toolchain corresponding to the local system when
+# doing cross-compiles. When not cross-compiling, this will be the same as the
+# default toolchain.
+#
+# We do this before anything else to make sure we complain about any
+# unsupported os/cpu combinations as early as possible.
+
+if (host_toolchain == "") {
+ # This should only happen in the top-level context.
+ # In a specific toolchain context, the toolchain_args()
+ # block should have propagated a value down.
+ # TODO(dpranke): Add some sort of assert here that verifies that
+ # no toolchain omitted host_toolchain from its toolchain_args().
+
+ if (host_os == "linux") {
+ if (target_os != "linux") {
+ host_toolchain = "//build/toolchain/linux:clang_$host_cpu"
+ } else if (is_clang) {
+ host_toolchain = "//build/toolchain/linux:clang_$host_cpu"
+ } else {
+ host_toolchain = "//build/toolchain/linux:$host_cpu"
+ }
+ } else if (host_os == "mac") {
+ host_toolchain = "//build/toolchain/mac:clang_$host_cpu"
+ } else if (host_os == "win") {
+ # On Windows always use the target CPU for host builds for x86/x64. On the
+ # configurations we support this will always work and it saves build steps.
+ # Windows ARM64 targets require an x64 host for cross build.
+ if (target_cpu == "x86" || target_cpu == "x64") {
+ if (is_clang) {
+ host_toolchain = "//build/toolchain/win:win_clang_$target_cpu"
+ } else {
+ host_toolchain = "//build/toolchain/win:$target_cpu"
+ }
+ } else if (is_clang) {
+ host_toolchain = "//build/toolchain/win:win_clang_$host_cpu"
+ } else {
+ host_toolchain = "//build/toolchain/win:$host_cpu"
+ }
+ } else if (host_os == "aix") {
+ host_toolchain = "//build/toolchain/aix:$host_cpu"
+ } else if (host_os == "zos") {
+ host_toolchain = "//build/toolchain/zos:$host_cpu"
+ } else {
+ assert(false, "Unsupported host_os: $host_os")
+ }
+}
+
+_default_toolchain = ""
+
+if (target_os == "android") {
+ assert(host_os == "linux", "Android builds are only supported on Linux.")
+ _default_toolchain = "//build/toolchain/android:android_clang_$target_cpu"
+} else if (target_os == "chromeos" || target_os == "linux") {
+ # See comments in build/toolchain/cros/BUILD.gn about board compiles.
+ if (is_clang) {
+ _default_toolchain = "//build/toolchain/linux:clang_$target_cpu"
+ } else {
+ _default_toolchain = "//build/toolchain/linux:$target_cpu"
+ }
+} else if (target_os == "fuchsia") {
+ _default_toolchain = "//build/toolchain/fuchsia:$target_cpu"
+} else if (target_os == "ios") {
+ _default_toolchain = "//build/toolchain/ios:ios_clang_$target_cpu"
+} else if (target_os == "mac") {
+ assert(host_os == "mac" || host_os == "linux",
+ "Mac cross-compiles are unsupported.")
+ _default_toolchain = "//build/toolchain/mac:clang_$target_cpu"
+} else if (target_os == "win") {
+ # On Windows, we use the same toolchain for host and target by default.
+ # Beware, win cross builds have some caveats, see docs/win_cross.md
+ if (is_clang) {
+ _default_toolchain = "//build/toolchain/win:win_clang_$target_cpu"
+ } else {
+ _default_toolchain = "//build/toolchain/win:$target_cpu"
+ }
+} else if (target_os == "winuwp") {
+ # Only target WinUWP on for a Windows store application and only
+ # x86, x64 and arm are supported target CPUs.
+ assert(target_cpu == "x86" || target_cpu == "x64" || target_cpu == "arm" ||
+ target_cpu == "arm64")
+ _default_toolchain = "//build/toolchain/win:uwp_$target_cpu"
+} else if (target_os == "aix") {
+ _default_toolchain = "//build/toolchain/aix:$target_cpu"
+} else if (target_os == "zos") {
+ _default_toolchain = "//build/toolchain/zos:$target_cpu"
+} else {
+ assert(false, "Unsupported target_os: $target_os")
+}
+
+# If a custom toolchain has been set in the args, set it as default. Otherwise,
+# set the default toolchain for the platform (if any).
+if (custom_toolchain != "") {
+ set_default_toolchain(custom_toolchain)
+} else if (_default_toolchain != "") {
+ set_default_toolchain(_default_toolchain)
+}
+
+# =============================================================================
+# OS DEFINITIONS
+# =============================================================================
+#
+# We set these various is_FOO booleans for convenience in writing OS-based
+# conditions.
+#
+# - is_android, is_chromeos, is_ios, and is_win should be obvious.
+# - is_mac is set only for desktop Mac. It is not set on iOS.
+# - is_posix is true for mac and any Unix-like system (basically everything
+# except Fuchsia and Windows).
+# - is_linux is true for desktop Linux, but not for ChromeOS nor Android (which
+# is generally too different despite being based on the Linux kernel).
+#
+# Do not add more is_* variants here for random lesser-used Unix systems like
+# aix or one of the BSDs. If you need to check these, just check the
+# current_os value directly.
+
+is_android = current_os == "android"
+is_chromeos = current_os == "chromeos"
+is_fuchsia = current_os == "fuchsia"
+is_ios = current_os == "ios"
+is_linux = current_os == "linux"
+is_mac = current_os == "mac"
+is_nacl = current_os == "nacl"
+is_win = current_os == "win" || current_os == "winuwp"
+
+is_apple = is_ios || is_mac
+is_posix = !is_win && !is_fuchsia
+
+# =============================================================================
+# TARGET DEFAULTS
+# =============================================================================
+#
+# Set up the default configuration for every build target of the given type.
+# The values configured here will be automatically set on the scope of the
+# corresponding target. Target definitions can add or remove to the settings
+# here as needed.
+#
+# WHAT GOES HERE?
+#
+# Other than the main compiler and linker configs, the only reason for a config
+# to be in this list is if some targets need to explicitly override that config
+# by removing it. This is how targets opt-out of flags. If you don't have that
+# requirement and just need to add a config everywhere, reference it as a
+# sub-config of an existing one, most commonly the main "compiler" one.
+
+# Holds all configs used for running the compiler.
+default_compiler_configs = [
+ "//build/config:feature_flags",
+ "//build/config/compiler:afdo",
+ "//build/config/compiler:afdo_optimize_size",
+ "//build/config/compiler:cet_shadow_stack",
+ "//build/config/compiler:chromium_code",
+ "//build/config/compiler:compiler",
+ "//build/config/compiler:compiler_arm_fpu",
+ "//build/config/compiler:compiler_arm_thumb",
+ "//build/config/compiler:default_include_dirs",
+ "//build/config/compiler:default_init_stack_vars",
+ "//build/config/compiler:default_optimization",
+ "//build/config/compiler:default_stack_frames",
+ "//build/config/compiler:default_symbols",
+ "//build/config/compiler:export_dynamic",
+ "//build/config/compiler:no_exceptions",
+ "//build/config/compiler:no_rtti",
+ "//build/config/compiler:no_unresolved_symbols",
+ "//build/config/compiler:runtime_library",
+ "//build/config/compiler:thin_archive",
+ "//build/config/compiler:thinlto_optimize_default",
+ "//build/config/compiler/pgo:default_pgo_flags",
+ "//build/config/coverage:default_coverage",
+ "//build/config/sanitizers:default_sanitizer_flags",
+]
+
+if (is_win) {
+ default_compiler_configs += [
+ "//build/config/win:default_cfg_compiler",
+ "//build/config/win:default_crt",
+ "//build/config/win:lean_and_mean",
+ "//build/config/win:nominmax",
+ "//build/config/win:unicode",
+ "//build/config/win:winver",
+ ]
+}
+
+if (is_posix) {
+ if (current_os != "aix") {
+ default_compiler_configs +=
+ [ "//build/config/gcc:symbol_visibility_hidden" ]
+ }
+}
+
+if (is_fuchsia) {
+ default_compiler_configs += [ "//build/config/gcc:symbol_visibility_hidden" ]
+}
+
+if (is_android) {
+ default_compiler_configs +=
+ [ "//build/config/android:default_orderfile_instrumentation" ]
+}
+
+if (is_clang && !is_nacl) {
+ default_compiler_configs += [
+ "//build/config/clang:find_bad_constructs",
+ "//build/config/clang:extra_warnings",
+ ]
+}
+
+# Debug/release-related defines.
+if (is_debug) {
+ default_compiler_configs += [ "//build/config:debug" ]
+} else {
+ default_compiler_configs += [ "//build/config:release" ]
+}
+
+# =============================================================================
+# Begin PDFIUM MODIFICATIONS
+# =============================================================================
+default_compiler_configs += [ "//build_overrides/compiler:force_cxx17" ]
+
+# =============================================================================
+# End PDFIUM MODIFICATIONS
+# =============================================================================
+
+# Static libraries and source sets use only the compiler ones.
+set_defaults("static_library") {
+ configs = default_compiler_configs
+}
+set_defaults("source_set") {
+ configs = default_compiler_configs
+}
+set_defaults("rust_library") {
+ configs = default_compiler_configs
+}
+set_defaults("rust_proc_macro") {
+ configs = default_compiler_configs
+}
+
+# Compute the set of configs common to all linked targets (shared libraries,
+# loadable modules, executables) to avoid duplication below.
+if (is_win) {
+ # Many targets remove these configs, so they are not contained within
+ # //build/config:executable_config for easy removal.
+ _linker_configs = [
+ "//build/config/win:default_incremental_linking",
+
+ # Default to console-mode apps. Most of our targets are tests and such
+ # that shouldn't use the windows subsystem.
+ "//build/config/win:console",
+ ]
+} else if (is_mac) {
+ _linker_configs = [ "//build/config/mac:strip_all" ]
+} else {
+ _linker_configs = []
+}
+
+# Executable defaults.
+default_executable_configs = default_compiler_configs + [
+ "//build/config:default_libs",
+ "//build/config:executable_config",
+ ] + _linker_configs
+
+if (is_win) {
+ # Turn on linker CFI for executables, and position it so it can be removed
+ # if needed.
+ default_executable_configs += [ "//build/config/win:cfi_linker" ]
+}
+
+set_defaults("executable") {
+ configs = default_executable_configs
+}
+
+# Shared library and loadable module defaults (also for components in component
+# mode).
+default_shared_library_configs = default_compiler_configs + [
+ "//build/config:default_libs",
+ "//build/config:shared_library_config",
+ ] + _linker_configs
+if (is_win) {
+ # Turn on linker CFI for DLLs, and position it so it can be removed if needed.
+ default_shared_library_configs += [ "//build/config/win:cfi_linker" ]
+}
+
+if (is_android) {
+ # Strip native JNI exports from shared libraries by default. Binaries that
+ # want this can remove this config.
+ default_shared_library_configs +=
+ [ "//build/config/android:hide_all_but_jni_onload" ]
+}
+set_defaults("shared_library") {
+ configs = default_shared_library_configs
+}
+set_defaults("loadable_module") {
+ configs = default_shared_library_configs
+
+ # loadable_modules are generally used by other libs, not just via JNI.
+ if (is_android) {
+ configs -= [ "//build/config/android:hide_all_but_jni_onload" ]
+ }
+}
+
+# A helper for forwarding testonly and visibility.
+# Forwarding "*" does not include variables from outer scopes (to avoid copying
+# all globals into each template invocation), so it will not pick up
+# file-scoped or outer-template-scoped variables. Normally this behavior is
+# desired, but "visibility" and "testonly" are commonly defined in outer scopes.
+# Explicitly forwarding them in forward_variables_from() works around this
+# nuance. See //build/docs/writing_gn_templates.md#using-forward_variables_from
+TESTONLY_AND_VISIBILITY = [
+ "testonly",
+ "visibility",
+]
+
+# Sets default dependencies for executable and shared_library targets.
+#
+# Variables
+# no_default_deps: If true, no standard dependencies will be added.
+# Targets that set this usually also want to remove
+# "//build/config/compiler:runtime_library" from configs (to remove
+# its subconfig "//build/config/c++:runtime_library").
+foreach(_target_type,
+ [
+ "executable",
+ "loadable_module",
+ "shared_library",
+ ]) {
+ template(_target_type) {
+ # Alias "target_name" because it is clobbered by forward_variables_from().
+ _target_name = target_name
+ target(_target_type, _target_name) {
+ forward_variables_from(invoker,
+ "*",
+ TESTONLY_AND_VISIBILITY + [ "no_default_deps" ])
+ forward_variables_from(invoker, TESTONLY_AND_VISIBILITY)
+ if (!defined(deps)) {
+ deps = []
+ }
+ if (!defined(invoker.no_default_deps) || !invoker.no_default_deps) {
+ # This pulls in one of:
+ # //build/config:executable_deps
+ # //build/config:loadable_module_deps
+ # //build/config:shared_library_deps
+ # (This explicit list is so that grepping for these configs finds where
+ # they are used.)
+ deps += [ "//build/config:${_target_type}_deps" ]
+ }
+
+ # On Android, write shared library output file to metadata. We will use
+ # this information to, for instance, collect all shared libraries that
+ # should be packaged into an APK.
+ if (!defined(invoker.metadata) && (is_android || is_robolectric) &&
+ (_target_type == "shared_library" ||
+ _target_type == "loadable_module")) {
+ _output_name = _target_name
+ if (defined(invoker.output_name)) {
+ _output_name = invoker.output_name
+ }
+
+ # Remove 'lib' prefix from output name if it exists.
+ _magic_prefix = "$0x01$0x01"
+ _output_name = string_replace("${_magic_prefix}${_output_name}",
+ "${_magic_prefix}lib",
+ _magic_prefix,
+ 1)
+ _output_name = string_replace(_output_name, _magic_prefix, "", 1)
+
+ if (defined(output_extension)) {
+ _shlib_extension = ".$output_extension"
+ } else if (is_component_build && _target_type != "loadable_module") {
+ _shlib_extension = ".cr.so"
+ } else {
+ _shlib_extension = ".so"
+ }
+
+ metadata = {
+ shared_libraries =
+ [ "$root_out_dir/lib${_output_name}${_shlib_extension}" ]
+ }
+ }
+ }
+ }
+}
+
+# ==============================================================================
+# COMPONENT SETUP
+# ==============================================================================
+
+# Defines a component, which equates to a shared_library when
+# is_component_build == true and a static_library otherwise.
+#
+# Use static libraries for the static build rather than source sets because
+# many of of our test binaries link many large dependencies but often don't
+# use large portions of them. The static libraries are much more efficient to
+# link in this situation since only the necessary object files are linked.
+#
+# The invoker can override the type of the target in the non-component-build
+# case by setting static_component_type to either "source_set" or
+# "static_library". If unset, the default will be used.
+template("component") {
+ if (is_component_build) {
+ _component_mode = "shared_library"
+ } else if (defined(invoker.static_component_type)) {
+ assert(invoker.static_component_type == "static_library" ||
+ invoker.static_component_type == "source_set")
+ _component_mode = invoker.static_component_type
+ } else if (!defined(invoker.sources) || invoker.sources == []) {
+ # When there are no sources defined, use a source set to avoid creating
+ # an empty static library (which generally don't work).
+ _component_mode = "source_set"
+ } else {
+ _component_mode = "static_library"
+ }
+ target(_component_mode, target_name) {
+ forward_variables_from(invoker, TESTONLY_AND_VISIBILITY)
+ forward_variables_from(invoker, "*", TESTONLY_AND_VISIBILITY)
+ }
+}
+
+# Component defaults
+# Set a variable since we also want to make this available
+# to mixed_component.gni
+if (is_component_build) {
+ default_component_configs = default_shared_library_configs
+ if (is_android) {
+ default_component_configs -=
+ [ "//build/config/android:hide_all_but_jni_onload" ]
+ }
+} else {
+ default_component_configs = default_compiler_configs
+}
+
+set_defaults("component") {
+ configs = default_component_configs
+}
diff --git a/build_overrides/compiler/BUILD.gn b/build_overrides/compiler/BUILD.gn
new file mode 100644
index 0000000..b6cc641
--- /dev/null
+++ b/build_overrides/compiler/BUILD.gn
@@ -0,0 +1,25 @@
+# Copyright 2022 The PDFium Authors
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# A simplified config to consistently use C++17 and override the config
+# in //build/config/compiler, which is using C++20 by default on many platforms.
+
+assert(!is_nacl)
+
+config("force_cxx17") {
+ cflags_cc = []
+
+ if (is_linux || is_chromeos || is_android || current_os == "aix") {
+ if (is_clang) {
+ standard_prefix = "c"
+ } else {
+ standard_prefix = "gnu"
+ }
+ cflags_cc += [ "-std=${standard_prefix}++17" ]
+ } else if (is_win) {
+ cflags_cc += [ "/std:c++17" ]
+ } else {
+ cflags_cc += [ "-std=c++17" ]
+ }
+}
