scripts/dawn_component.gni

# Copyright 2019 The Dawn & Tint Authors
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# 1. Redistributions of source code must retain the above copyright notice, this
#    list of conditions and the following disclaimer.
#
# 2. Redistributions in binary form must reproduce the above copyright notice,
#    this list of conditions and the following disclaimer in the documentation
#    and/or other materials provided with the distribution.
#
# 3. Neither the name of the copyright holder nor the names of its
#    contributors may be used to endorse or promote products derived from
#    this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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) {
      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
    }

    # If a "build with ARC" config is present, remove it.
    if (filter_include(configs, [ "//build/config/compiler:enable_arc" ]) !=
        []) {
      configs -= [ "//build/config/compiler:enable_arc" ]
    }

    # 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 (is_android) {
      configs -= [ "//build/config/android:hide_all_but_jni_onload" ]
    }
  }

  if (dawn_complete_static_libs) {
    # Use static_library if explicitly requested - this works even if there are
    # no sources in the target by linking in sources from all dependencies.
    _static_target_type = "static_library"
  } 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).
    _static_target_type = "source_set"
  } else {
    # 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
    # in this situation since only the necessary object files are linked.
    _static_target_type = "static_library"
  }

  target(_static_target_type, "${prefix}static") {
    output_name = "dawn_${name}_static"

    if (dawn_complete_static_libs) {
      assert(_static_target_type == "static_library")
      complete_static_lib = true
    }

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

    # If a "build with ARC" config is present, remove it.
    if (filter_include(configs, [ "//build/config/compiler:enable_arc" ]) !=
        []) {
      configs -= [ "//build/config/compiler:enable_arc" ]
    }
  }

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