scripts/dawn_component.gni

# Copyright 2019 The Dawn 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
#
#     http://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.

import("//build_overrides/build.gni")
import("dawn_features.gni")
import("dawn_overrides_with_defaults.gni")

###############################################################################
# Template to produce a component for one of Dawn's libraries.
###############################################################################

# Template that produces static and shared versions of the same library as well
# as a target similar to Chromium's component targets.
#  - The shared version exports symbols and has dependent import the symbols
#    as libdawn_${name}.so. If the target name matches the package directory
#    name, then the shared library target will be named 'shared', otherwise
#    '${target_name}_shared'.
#  - The static library doesn't export symbols nor make dependents import them.
#    If the target name matches the package directory name, then the static
#    library target will be named 'static', otherwise '${target_name}_static'.
#  - The libname target is similar to a Chromium component and is an alias for
#    either the static or the shared library.
#
# The DEFINE_PREFIX must be provided and must match the respective "_export.h"
# file.
#
# Example usage:
#
#   dawn_component("my_library") {
#     // my_library_export.h must use the MY_LIBRARY_IMPLEMENTATION and
#     // MY_LIBRARY_SHARED_LIBRARY macros.
#     DEFINE_PREFIX = "MY_LIBRARY"
#
#     sources = [...]
#     deps = [...]
#     configs = [...]
#   }
#
#   executable("foo") {
#     deps = [ ":my_library_shared" ] // or :my_library for the same effect
#   }
template("dawn_component") {
  # Copy the target_name in the local scope so it doesn't get shadowed in the
  # definition of targets.
  name = target_name

  prefix = "${name}_"

  # Remove prefix if the target name matches directory
  if (get_label_info(get_label_info(":$target_name", "dir"), "name") == name) {
    prefix = ""
  }

  # The config that will apply to dependents of the shared library so they know
  # they should "import" the symbols
  config("${prefix}shared_public_config") {
    defines = [ "${invoker.DEFINE_PREFIX}_SHARED_LIBRARY" ]

    # Executable needs an rpath to find our shared libraries on OSX and Linux
    if (is_mac) {
      ldflags = [
        "-rpath",
        "@executable_path/",
      ]
    }
    if ((is_linux || is_chromeos) && dawn_has_build) {
      configs = [ "//build/config/gcc:rpath_for_built_shared_libraries" ]
    }
  }

  shared_library("${prefix}shared") {
    # The "tool" for creating shared libraries will automatically add the "lib" prefix
    output_name = "dawn_${name}"

    # Copy all variables except "configs", which has a default value
    forward_variables_from(invoker, "*", [ "configs" ])
    if (defined(invoker.configs)) {
      configs += invoker.configs
    }

    # Tell dependents where to find this shared library
    if (is_mac) {
      ldflags = [
        "-install_name",
        "@rpath/lib${name}.dylib",
      ]
    }

    # Use the config that makes the ${DEFINE_PREFIX}_EXPORT macro do something
    if (!defined(public_configs)) {
      public_configs = []
    }
    public_configs += [ ":${prefix}shared_public_config" ]

    # Tell sources of this library to export the symbols (and not import)
    if (!defined(defines)) {
      defines = []
    }
    defines += [ "${invoker.DEFINE_PREFIX}_IMPLEMENTATION" ]

    # Chromium adds a config that uses a special linker script that removes
    # all symbols except JNI ones. Remove this config so that our
    # shared_library symbols are visible. This matches what Chromium's
    # component template does.
    if (build_with_chromium && is_android) {
      configs -= [ "//build/config/android:hide_all_but_jni_onload" ]
    }
  }

  static_library("${prefix}static") {
    output_name = "dawn_${name}_static"

    complete_static_lib = dawn_complete_static_libs

    # Copy all variables except "configs", which has a default value
    forward_variables_from(invoker, "*", [ "configs" ])
    if (defined(invoker.configs)) {
      configs += invoker.configs
    }
  }

  group(name) {
    if (is_component_build) {
      public_deps = [ ":${prefix}shared" ]
    } else {
      public_deps = [ ":${prefix}static" ]
    }
  }
}