pw_build/multi_toolchain_group.gni

# Copyright 2021 The Pigweed Authors
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may not
# use this file except in compliance with the License. You may obtain a copy of
# the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations under
# the License.

# Declares a group that builds a list of dependencies using multiple toolchains.
#
# In a multi-toolchain group, each dependency is built with each of the provided
# toolchains. This results in M x N targets being built, where M is the number
# of toolchains, and N is the number of targets listed in the `deps` variable.
#
# This template is useful for simplifying cases where you have multiple
# applications you would like to build under different toolchain contexts.
#
# Args:
#   deps: (required) List of GN targets to build under each listed toolchain.
#   toolchains: (required) A list of toolchain labels to build the dependencies
#     with.
template("pw_multi_toolchain_group") {
  assert(!defined(invoker.public_deps),
         "Use `deps` for pw_multi_toolchain_group targets")
  assert(defined(invoker.deps), "`deps` must be defined to use this template")
  assert(defined(invoker.toolchains),
         "`toolchains` must be defined to use this template")
  group(target_name) {
    deps = []
    public_deps = []
    foreach(tc, invoker.toolchains) {
      foreach(item, invoker.deps) {
        # Make sure targets don't explicitly reference a toolchain in their
        # target label. If we poison any instances of "(", we can see a mismatch
        # against the original string, indicating a toolchain was explicitly
        # specified.
        _poisioned_label = string_replace(item, "(", "!")
        assert(item == _poisioned_label,
               "$item can't explicitly specify a toolchain as part of " +
                   "a multi-toolchain group")
        deps += [ "$item($tc)" ]
      }
    }
  }
}