# Copyright 2021 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.

#  ________  _________  ________  ________
# |\   ____\|\___   ___\\   __  \|\   __  \
# \ \  \___|\|___ \  \_\ \  \|\  \ \  \|\  \
#  \ \_____  \   \ \  \ \ \  \\\  \ \   ____\
#   \|____|\  \   \ \  \ \ \  \\\  \ \  \___|
#     ____\_\  \   \ \__\ \ \_______\ \__\
#    |\_________\   \|__|  \|_______|\|__|
#    \|_________|
#
# Here to enable an unstable feature? All unstable features require special
# approval because they create risk and may have stable alternatives that better
# fit our needs. See the "Unstable features" section for more information.

import("//build/images/filesystem_limits.gni")
import("//build/rust/config.gni")
import("//build/toolchain/rbe.gni")

declare_args() {
  # Controls whether the rust compiler uses v0 symbol mangling scheme
  # (see https://github.com/rust-lang/rfcs/blob/HEAD/text/2603-rust-symbol-name-mangling-v0.md).
  # The v0 symbol mangling scheme requires upstream LLVM support when demangling,
  # so it is not on by default.
  # TODO(fxbug.dev/57302): Enable v0 mangling by default.
  rust_v0_symbol_mangling = false

  # Enable incremental rust compilation. Takes a path to the directory to use
  # as the cache.
  rust_incremental = ""
}

# Defines a Rust cfg flag with the value of the rust_panic build arg.
# Useful for changing behavior of code based on panic behavior.
config("panic_cfg") {
  rustflags = [ "--cfg=rust_panic=\"${rust_panic}\"" ]
}

# Turns on the rust compilation analysis generator. This will produce a
# directory $OUT/save-analysis-temp, which will dump all the source analysis
# that the compiler collected while analyzing the source.  This config is
# included conditionally, see //build/config/BUILDCONFIG.gn for details.
config("analysis") {
  rustflags = [ "-Zsave-analysis" ]
}

config("edition_2021") {
  rustflags = [ "--edition=2021" ]
}

config("edition_2018") {
  rustflags = [ "--edition=2018" ]
}

config("edition_2015") {
  rustflags = [ "--edition=2015" ]
}

config("no_features") {
  rustflags = [ "-Zallow-features=" ]
}

config("incremental") {
  if (rust_incremental != "") {
    rustflags = [ "-Cincremental=" + rust_incremental ]
  }
}

config("one_codegen_unit") {
  # Disable codegen parallelism.
  # Trades incremental rebuild speed for smaller code size.
  # See: fxbug.dev/74435, fxbug.dev/80514
  if (rust_incremental == "") {
    rustflags = [ "-Ccodegen-units=1" ]
  }
}

config("codegen_units_16") {
  # Enable default codegen parallelism (rustc default).
  # This will increase code size over `:one_codegen_unit` above.
  #
  # Used without any lto option, this will also enable thin-local lto.
  # https://doc.rust-lang.org/rustc/codegen-options/index.html#lto
  if (rust_incremental == "") {
    rustflags = [ "-Ccodegen-units=16" ]
  }
}

config("lto_disabled") {
  # Fully disable lto.
  #
  # This is the default when -Ccodegen_units=1 or when optimizations are off
  # (-Copt-level=0)
  rustflags = [ "-Clto=off" ]
}

config("lto_thin") {
  # Enable "thin" lto across all crates being linked
  rustflags = [ "-Clto=thin" ]
}

# Best practices for Rust binaries that go into size-constrained bootfs.
config("bootfs") {
  # Optimize for size.
  # TODO(fxbug.dev/63313): use "z" when resolved.
  rustflags = [ "-Copt-level=s" ]

  if (is_debug &&  # Debug builds produce large Rust binaries
      max_fuchsia_zbi_size > 0) {  # So large they might not fit in the ZBI
    # Force ThinLTO to squeeze Rust binaries further.
    # See: fxbug.dev/80514
    # See: fxbug.dev/91325
    configs = [ "//build/config/lto:thinlto" ]
  }

  # Can't dynamically link libstd and libtest for ZBI binaries.
  # TODO(fxbug.dev/83081): reconsider this.
  rustflags += [ "-Cprefer-dynamic=no" ]
}

config("proc_macro_test") {
  rustflags = [
    "--extern",
    "proc_macro",
  ]
}

config("2018_idioms") {
  rustflags = [ "-Wrust-2018-idioms" ]
}

config("target") {
  rustflags = [
    "--target",
    rust_target,
    "--cap-lints=$rust_cap_lints",
  ]
}

config("panic_abort") {
  rustflags = [
    "-Cpanic=abort",
    "-Cforce-unwind-tables=yes",
    "-Zpanic_abort_tests",
  ]
}

config("v0_symbol_mangling") {
  if (rust_v0_symbol_mangling) {
    rustflags = [ "-Csymbol-mangling-version=v0" ]
  }
}

config("allow_unknown_lints") {
  rustflags = [ "-Aunknown-lints" ]
}

# TODO(fxbug.dev/67118) remove this allowance
config("allow_redundant_semicolons") {
  rustflags = [ "-Aredundant-semicolons" ]
}

# TODO(fxbug.dev/69442) remove this allowance
config("allow_legacy_derive_helpers") {
  rustflags = [ "-Alegacy-derive-helpers" ]
}

config("deny_unused_results") {
  rustflags = [ "-Dunused_results" ]
}

config("allow_unused_results") {
  rustflags = [ "-Aunused_results" ]

  # This visibility list allows for targets to opt out of allowing unused results.
  #
  # There is currently no platform mandate to adopt the unused_results lint and it's opt-in for
  # developers that want to use it. See https://fxbug.dev/73468 for more context.
  #
  # To adopt the lint, add the following to your rust target:
  #   configs -= ["//build/config/rust:allow_unused_results"]
  # The visibility list below can be used to enforce the list on certain areas of the tree while
  # we evaluate wider adoption.
  #
  # To update this list run:
  # $ scripts/gn/gen_visibility_globs.py \
  #    --all=//build/config/rust:deny_unused_results \
  #    --allow=//build/config/rust:allow_unused_results \
  #    --ignore-suffix=-rustc,_banjo_rust
  visibility = [
    "//build/*",
    "//examples/*",
    "//garnet/*",
    "//sdk/*",
    "//src/bringup/*",
    "//src/camera/*",
    "//src/cobalt/*",
    "//src/connectivity/bluetooth/lib/bt-a2dp:*",
    "//src/connectivity/location/*",
    "//src/connectivity/lowpan/*",
    "//src/connectivity/network/net-cli/ffx:*",
    "//src/connectivity/network/netstack:networking_metrics_rustlib",
    "//src/connectivity/network/testing/network-test-realm/ffx:*",
    "//src/connectivity/openthread/*",
    "//src/connectivity/overnet/*",
    "//src/connectivity/ppp/*",
    "//src/connectivity/telephony/*",
    "//src/connectivity/weave/*",
    "//src/connectivity/wlan/*",
    "//src/developer/*",
    "//src/devices/*",
    "//src/diagnostics/*",
    "//src/experiences/*",
    "//src/factory/*",
    "//src/fonts/*",
    "//src/graphics/*",
    "//src/hwinfo/*",
    "//src/identity/*",
    "//src/intl/*",
    "//src/lib/*",
    "//src/media/*",
    "//src/modular/*",
    "//src/power/*",
    "//src/proc/*",
    "//src/recovery/*",
    "//src/security/*",
    "//src/session/*",
    "//src/settings/*",
    "//src/storage/*",
    "//src/sys/*",
    "//src/testing/*",
    "//src/tests/*",
    "//src/ui/*",
    "//src/virtualization/*",
    "//src/zircon/*",
    "//third_party/*",
    "//tools/*",
    "//vendor/*",
    "//zircon/*",
  ]
}

config("coverage") {
  rustflags = [ "-Cinstrument-coverage" ]
}

# TODO(fxbug.dev/94355): Eliminate or identify all sources of output dir leaks.
# This option makes it explicit that a particular build action is sensitive
# to the output dir path, and informs remote execution to refrain from
# normalizing the output dir, which improves caching.
# As a goal, we should aim to minimize the need for this config.
config("output_dir_sensitive") {
  if (rust_rbe_enable) {
    # --remote-flag=* is a pseudo flag that is intercepted by
    # build/rbe/rustc-remote-wrapper.sh and forwarded to rewrapper (reclient).
    rustflags = [ "--remote-flag=--canonicalize_working_dir=false" ]
  }
}

# Unstable features
#
# These configs enable unstable Rust features. Configs that enable unstable
# features must go through an approval process before they may be added. See:
# https://fuchsia.dev/fuchsia-src/development/languages/rust/unstable#the_process
#
# When adding a new config, make sure to add a TODO with a link to the tracking
# issue.

# TODO(fxbug.dev/98399)
config("netstack3_only_specialization_feature") {
  rustflags = [
    "-Zallow-features=min_specialization,specialization",
    "-Aincomplete-features",
  ]
}

# TODO(fxbug.dev/94237)
config("allow_simd") {
  rustflags = [ "-Zallow-features=stdsimd,aarch64_target_feature" ]
}

# TODO(fxbug.dev/103193)
config("allow_non_exhaustive_omitted_patterns_lint") {
  rustflags = [ "-Zallow-features=non_exhaustive_omitted_patterns_lint" ]
  visibility =
      [ "//src/connectivity/network/netstack3/core/specialize-ip-macro:*" ]
}