# Copyright 2019 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.

import("//build/config/clang/clang.gni")

# This template defines a toolchain.
#
# It requires the following variables specifying the executables to run:
#  - ar
#  - cc
#  - cxx
#  - ld
#
# Optional parameters that control the tools:
#
#  - extra_cflags
#      Extra flags to be appended when compiling C files (but not C++ files).
#  - extra_cppflags
#      Extra flags to be appended when compiling both C and C++ files. "CPP"
#      stands for "C PreProcessor" in this context, although it can be
#      used for non-preprocessor flags as well. Not to be confused with
#      "CXX" (which follows).
#  - extra_cxxflags
#      Extra flags to be appended when compiling C++ files (but not C files).
#  - extra_asmflags
#      Extra flags to be appended when compiling assembly.
#  - extra_ldflags
#      Extra flags to be appended when linking
#
#  - libs_section_prefix
#  - libs_section_postfix
#      The contents of these strings, if specified, will be placed around
#      the libs section of the linker line. It allows one to inject libraries
#      at the beginning and end for all targets in a toolchain.
#  - solink_libs_section_prefix
#  - solink_libs_section_postfix
#      Same as libs_section_{pre,post}fix except used for solink instead of link.
#  - link_outputs
#      The content of this array, if specified, will be added to the list of
#      outputs from the link command. This can be useful in conjunction with
#      the post_link parameter.
#  - use_unstripped_as_runtime_outputs
#      When |strip| is set, mark unstripped executables as runtime deps rather
#      than stripped ones.
#  - post_link
#      The content of this string, if specified, will be run as a separate
#      command following the the link command.
#  - deps
#      Just forwarded to the toolchain definition.
#  - executable_extension
#      If this string is specified it will be used for the file extension
#      for an executable, rather than using no extension; targets will
#      still be able to override the extension using the output_extension
#      variable.
#  - rebuild_define
#      The contents of this string, if specified, will be passed as a #define
#      to the toolchain. It can be used to force recompiles whenever a
#      toolchain is updated.
#  - shlib_extension
#      If this string is specified it will be used for the file extension
#      for a shared library, rather than default value specified in
#      toolchain.gni
#  - strip
#      Location of the strip executable. When specified, strip will be run on
#      all shared libraries and executables as they are built. The pre-stripped
#      artifacts will be put in lib.unstripped/ and exe.unstripped/.
template("clang_toolchain") {
  declare_args() {
    shlib_prefix = "lib"
    shlib_extension = ".so"
  }

  params = {
    if (defined(invoker.prefix)) {
      prefix = invoker.prefix
    } else {
      prefix = rebase_path("$clang_base_path/bin", root_build_dir)
    }
    if (defined(invoker.ar)) {
      ar = invoker.ar
    } else {
      ar = "${prefix}/llvm-ar"
    }

    if (defined(invoker.cc)) {
      cc = invoker.cc
    } else {
      cc = "${prefix}/clang"
    }

    if (defined(invoker.cxx)) {
      cxx = invoker.cxx
    } else {
      cxx = "${prefix}/clang++"
    }

    if (defined(invoker.ld)) {
      ld = invoker.ld
    } else {
      ld = cxx
    }
  }

  toolchain(target_name) {
    assert(defined(params.ar), "clang_toolchain() must specify a \"ar\" value")
    assert(defined(params.cc), "clang_toolchain() must specify a \"cc\" value")
    assert(defined(params.cxx), "clang_toolchain() must specify a \"cxx\" value")
    assert(defined(params.ld), "clang_toolchain() must specify a \"ld\" value")

    # This define changes when the toolchain changes, forcing a rebuild.
    # Nothing should ever use this define.
    if (defined(invoker.rebuild_define)) {
      rebuild_string = "-D" + invoker.rebuild_define + " "
    } else {
      rebuild_string = ""
    }

    # GN's syntax can't handle more than one scope dereference at once, like
    # "invoker.toolchain_args.foo", so make a temporary to hold the toolchain
    # args so we can do "invoker_toolchain_args.foo".
    assert(defined(invoker.toolchain_args),
           "Toolchains must specify toolchain_args")
    invoker_toolchain_args = invoker.toolchain_args
    assert(defined(invoker_toolchain_args.current_cpu),
           "toolchain_args must specify a current_cpu")
    assert(defined(invoker_toolchain_args.current_os),
           "toolchain_args must specify a current_os")

    # When invoking this toolchain not as the default one, these args will be
    # passed to the build. They are ignored when this is the default toolchain.
    toolchain_args = {
      # Populate toolchain args from the invoker.
      forward_variables_from(invoker_toolchain_args, "*")

      # The host toolchain value computed by the default toolchain's setup
      # needs to be passed through unchanged to all secondary toolchains to
      # ensure that it's always the same, regardless of the values that may be
      # set on those toolchains.
      host_toolchain = host_toolchain
    }

    compiler_prefix = " "

    # Create a distinct variable for "asm", since analysis runs pass # a bunch
    # of flags to clang/clang++ that are nonsensical on assembler runs.
    asm_prefix = compiler_prefix

    cc = compiler_prefix + params.cc
    cxx = compiler_prefix + params.cxx
    asm = asm_prefix + params.cc
    ar = params.ar
    ld = params.ld

    if (defined(invoker.shlib_extension)) {
      default_shlib_extension = invoker.shlib_extension
    } else {
      default_shlib_extension = shlib_extension
    }

    if (defined(invoker.default_shlib_subdir)) {
      default_shlib_subdir = invoker.default_shlib_subdir
    } else {
      default_shlib_subdir = ""
    }

    if (defined(invoker.executable_extension)) {
      default_executable_extension = invoker.executable_extension
    } else {
      default_executable_extension = ""
    }

    # Bring these into our scope for string interpolation with default values.
    if (defined(invoker.libs_section_prefix)) {
      libs_section_prefix = invoker.libs_section_prefix
    } else {
      libs_section_prefix = ""
    }

    if (defined(invoker.libs_section_postfix)) {
      libs_section_postfix = invoker.libs_section_postfix
    } else {
      libs_section_postfix = ""
    }

    if (defined(invoker.solink_libs_section_prefix)) {
      solink_libs_section_prefix = invoker.solink_libs_section_prefix
    } else {
      solink_libs_section_prefix = ""
    }

    if (defined(invoker.solink_libs_section_postfix)) {
      solink_libs_section_postfix = invoker.solink_libs_section_postfix
    } else {
      solink_libs_section_postfix = ""
    }

    if (defined(invoker.extra_cflags) && invoker.extra_cflags != "") {
      extra_cflags = " " + invoker.extra_cflags
    } else {
      extra_cflags = ""
    }

    if (defined(invoker.extra_cppflags) && invoker.extra_cppflags != "") {
      extra_cppflags = " " + invoker.extra_cppflags
    } else {
      extra_cppflags = ""
    }

    if (defined(invoker.extra_cxxflags) && invoker.extra_cxxflags != "") {
      extra_cxxflags = " " + invoker.extra_cxxflags
    } else {
      extra_cxxflags = ""
    }

    if (defined(invoker.extra_asmflags) && invoker.extra_asmflags != "") {
      extra_asmflags = " " + invoker.extra_asmflags
    } else {
      extra_asmflags = ""
    }

    if (defined(invoker.extra_ldflags) && invoker.extra_ldflags != "") {
      extra_ldflags = " " + invoker.extra_ldflags
    } else {
      extra_ldflags = ""
    }

    # These library switches can apply to all tools below.
    lib_switch = "-l"
    lib_dir_switch = "-L"

    # Object files go in this directory.
    object_subdir = "{{target_out_dir}}/{{label_name}}"

    tool("cc") {
      depfile = "{{output}}.d"
      command = "$cc -MMD -MF $depfile ${rebuild_string}{{defines}} {{include_dirs}} {{cflags}} {{cflags_c}}${extra_cppflags}${extra_cflags} -c {{source}} -o {{output}}"
      depsformat = "gcc"
      description = "CC {{output}}"
      outputs = [
        "$object_subdir/{{source_name_part}}.o",
      ]
    }

    tool("cxx") {
      depfile = "{{output}}.d"
      command = "$cxx -MMD -MF $depfile ${rebuild_string}{{defines}} {{include_dirs}} {{cflags}} {{cflags_cc}}${extra_cppflags}${extra_cxxflags} -c {{source}} -o {{output}}"
      depsformat = "gcc"
      description = "CXX {{output}}"
      outputs = [
        "$object_subdir/{{source_name_part}}.o",
      ]
    }

    tool("asm") {
      # For clang we can just use the C compiler to compile assembly.
      depfile = "{{output}}.d"
      command = "$asm -MMD -MF $depfile ${rebuild_string}{{defines}} {{include_dirs}} {{asmflags}}${extra_asmflags} -c {{source}} -o {{output}}"
      depsformat = "gcc"
      description = "ASM {{output}}"
      outputs = [
        "$object_subdir/{{source_name_part}}.o",
      ]
    }

    tool("alink") {
      rspfile = "{{output}}.rsp"
      rspfile_content = "{{inputs}}"
      command = "\"$ar\" {{arflags}} -r -c -s -D {{output}} @\"$rspfile\""

      # Remove the output file first so that ar doesn't try to modify the
      # existing file.
      command = "rm -f {{output}} && $command"

      # Almost all targets build with //build/config/compiler:thin_archive which
      # adds -T to arflags.
      description = "AR {{output}}"
      outputs = [
        "{{output_dir}}/{{target_output_name}}{{output_extension}}",
      ]

      # Shared libraries go in the target out directory by default so we can
      # generate different targets with the same name and not have them collide.
      default_output_dir = "{{target_out_dir}}"
      default_output_extension = ".a"
      output_prefix = "lib"
    }

    tool("solink") {
      soname = "{{target_output_name}}{{output_extension}}"  # e.g. "libfoo.so".
      sofile = "{{output_dir}}/$soname"  # Possibly including toolchain dir.
      rspfile = sofile + ".rsp"

      if (defined(invoker.strip)) {
        unstripped_sofile = "{{root_out_dir}}/lib.unstripped/$soname"
      } else {
        unstripped_sofile = sofile
      }

      # These variables are not built into GN but are helpers that
      # implement (1) linking to produce a .so, (2) extracting the symbols
      # from that file (3) if the extracted list differs from the existing
      # .TOC file, overwrite it, otherwise, don't change it.
      tocfile = sofile + ".TOC"

      link_command = "$ld -shared {{ldflags}}${extra_ldflags} -o \"$unstripped_sofile\" -Wl,-soname=\"$soname\" @\"$rspfile\""

      # Generate a map file to be used for binary size analysis.
      if (defined(invoker.strip)) {
        strip_switch = "--strip=${invoker.strip} "
      }

      command = "$link_command"
      rspfile_content = "-Wl,--whole-archive {{inputs}} {{solibs}} -Wl,--no-whole-archive $solink_libs_section_prefix {{libs}} $solink_libs_section_postfix"
      description = "SOLINK $sofile"

      # Use this for {{output_extension}} expansions unless a target manually
      # overrides it (in which case {{output_extension}} will be what the target
      # specifies).
      default_output_extension = default_shlib_extension

      default_output_dir = "{{root_out_dir}}${default_shlib_subdir}"

      output_prefix = "lib"

      # Since the above commands only updates the .TOC file when it changes, ask
      # Ninja to check if the timestamp actually changed to know if downstream
      # dependencies should be recompiled.
      restat = true

      # Tell GN about the output files. It will link to the sofile but use the
      # tocfile for dependency management.
      outputs = [
        sofile,
        tocfile,
      ]
      if (sofile != unstripped_sofile) {
        outputs += [ unstripped_sofile ]
        if (defined(invoker.use_unstripped_as_runtime_outputs) &&
            invoker.use_unstripped_as_runtime_outputs) {
          runtime_outputs = [ unstripped_sofile ]
        }
      }
      if (defined(map_file)) {
        outputs += [ map_file ]
      }
      link_output = sofile
      depend_output = tocfile
    }

    tool("solink_module") {
      soname = "{{target_output_name}}{{output_extension}}"  # e.g. "libfoo.so".
      sofile = "{{output_dir}}/$soname"
      rspfile = sofile + ".rsp"

      if (defined(invoker.strip)) {
        unstripped_sofile = "{{root_out_dir}}/lib.unstripped/$soname"
      } else {
        unstripped_sofile = sofile
      }

      command = "$ld -shared {{ldflags}}${extra_ldflags} -o \"$unstripped_sofile\" -Wl,-soname=\"$soname\" @\"$rspfile\""

      if (defined(invoker.strip)) {
        strip_command = "${invoker.strip} -o \"$sofile\" \"$unstripped_sofile\""
        command += " && " + strip_command
      }
      rspfile_content = "-Wl,--whole-archive {{inputs}} {{solibs}} -Wl,--no-whole-archive $solink_libs_section_prefix {{libs}} $solink_libs_section_postfix"

      description = "SOLINK_MODULE $sofile"

      # Use this for {{output_extension}} expansions unless a target manually
      # overrides it (in which case {{output_extension}} will be what the target
      # specifies).
      if (defined(invoker.loadable_module_extension)) {
        default_output_extension = invoker.loadable_module_extension
      } else {
        default_output_extension = default_shlib_extension
      }

      default_output_dir = "{{root_out_dir}}${default_shlib_subdir}"

      output_prefix = "lib"

      outputs = [
        sofile,
      ]
      if (sofile != unstripped_sofile) {
        outputs += [ unstripped_sofile ]
        if (defined(invoker.use_unstripped_as_runtime_outputs) &&
            invoker.use_unstripped_as_runtime_outputs) {
          runtime_outputs = [ unstripped_sofile ]
        }
      }
    }

    tool("link") {
      exename = "{{target_output_name}}{{output_extension}}"
      outfile = "{{output_dir}}/$exename"
      rspfile = "$outfile.rsp"
      unstripped_outfile = outfile

      # Use this for {{output_extension}} expansions unless a target manually
      # overrides it (in which case {{output_extension}} will be what the target
      # specifies).
      default_output_extension = default_executable_extension

      default_output_dir = "{{root_out_dir}}"

      if (defined(invoker.strip)) {
        unstripped_outfile = "{{root_out_dir}}/exe.unstripped/$exename"
      }

      # Generate a map file to be used for binary size analysis.
      # Map file adds ~10% to the link time on a z620.
      # With target_os="android", libchrome.so.map.gz is ~20MB.
      start_group_flag = "-Wl,--start-group"
      end_group_flag = "-Wl,--end-group "
      link_command = "$ld {{ldflags}}${extra_ldflags} -o \"$unstripped_outfile\" $start_group_flag @\"$rspfile\" {{solibs}} $end_group_flag $libs_section_prefix {{libs}} $libs_section_postfix"

      command = "$link_command"
      description = "LINK $outfile"
      rspfile_content = "{{inputs}}"
      outputs = [
        outfile,
      ]
      if (outfile != unstripped_outfile) {
        outputs += [ unstripped_outfile ]
        if (defined(invoker.use_unstripped_as_runtime_outputs) &&
            invoker.use_unstripped_as_runtime_outputs) {
          runtime_outputs = [ unstripped_outfile ]
        }
      }
      if (defined(invoker.link_outputs)) {
        outputs += invoker.link_outputs
      }
      if (defined(map_file)) {
        outputs += [ map_file ]
      }
    }

    # These two are really entirely generic, but have to be repeated in
    # each toolchain because GN doesn't allow a template to be used here.
    # See //build/toolchain/toolchain.gni for details.
    tool("stamp") {
      command = "touch {{output}}"
      description = "STAMP {{output}}"
    }
    tool("copy") {
      command = "ln -f {{source}} {{output}} 2>/dev/null || (rm -rf {{output}} && cp -af {{source}} {{output}})"
      description = "COPY {{source}} {{output}}"
    }

    forward_variables_from(invoker, [ "deps" ])
  }
}