declare_args() {
  host_ar = ar
  host_cc = cc
  host_cxx = cxx

  if (is_android) {
    _prefix = "$ndk/toolchains/llvm/prebuilt/$ndk_host/bin"
    if (host_os == "win") {
      target_ar = "$_prefix/llvm-ar.exe"
      target_cc = "$_prefix/clang.exe --target=$ndk_target$ndk_api -fno-addrsig"
      target_cxx =
          "$_prefix/clang++.exe --target=$ndk_target$ndk_api -fno-addrsig"
    } else {
      target_ar = "$_prefix/llvm-ar"
      target_cc = "$_prefix/$ndk_target$ndk_api-clang"
      target_cxx = "$_prefix/$ndk_target$ndk_api-clang++"
    }
  } else {
    target_ar = ar
    target_cc = cc
    target_cxx = cxx
  }

  cc_wrapper = ""

  # dsymutil seems to kill the machine when too many processes are run in
  # parallel, so we need to use a pool to limit the concurrency when passing
  # large -j to Ninja (e.g. Goma build). Unfortunately this is also one of the
  # slowest steps in a build, so we don't want to limit too much. Use the number
  # of CPUs as a default.
  dlsymutil_pool_depth = exec_script("num_cpus.py", [], "value")
}

if (host_os == "win") {
  stamp = "cmd.exe /c echo >"
} else {
  stamp = "touch"
}

if (current_toolchain == default_toolchain) {
  pool("dsymutil_pool") {
    depth = dlsymutil_pool_depth
  }
}

toolchain("msvc") {
  lib_dir_switch = "/LIBPATH:"

  bin = "$win_vc/Tools/MSVC/$win_toolchain_version/bin/HostX64/$target_cpu"

  env_setup = ""
  if (target_cpu == "x86") {
    # Toolchain asset includes a script that configures for x86 building.
    # We don't support x86 builds with local MSVC installations.
    env_setup = "cmd /c $win_sdk/bin/SetEnv.cmd /x86 && "
  } else if (target_cpu == "arm64") {
    # ARM64 compiler is incomplete - it relies on DLLs located in the host toolchain directory.
    env_setup = "cmd /C set \"PATH=%PATH%;$win_vc\\Tools\\MSVC\\$win_toolchain_version\\bin\\HostX64\\x64\" && "
  }

  cl_m32_flag = ""

  if (clang_win != "") {
    if (target_cpu == "x86") {
      # cl.exe knows implicitly by the choice of executable that it's targeting
      # x86, but clang-cl.exe needs to be told when targeting non-host
      # platforms. (All our builders are x86-64, so x86 is always non-host.)
      cl_m32_flag = "-m32"
    }
    if (host_os == "win") {
      cl = "\"$clang_win/bin/clang-cl.exe\""
      lib = "\"$clang_win/bin/lld-link.exe\" /lib"
      link = "\"$clang_win/bin/lld-link.exe\""
    } else {
      cl = "\"$clang_win/bin/clang-cl\""
      lib = "\"$clang_win/bin/lld-link\" /lib"
      link = "\"$clang_win/bin/lld-link\""
    }
  } else {
    cl = "\"$bin/cl.exe\""
    lib = "\"$bin/lib.exe\""
    link = "\"$bin/link.exe\""
  }

  tool("asm") {
    _ml = "ml"
    if (target_cpu == "x64") {
      _ml += "64"
    }
    command = "$env_setup \"$bin/$_ml.exe\" {{asmflags}} /nologo /c /Fo {{output}} {{source}}"
    outputs = [
      "{{source_out_dir}}/{{target_output_name}}.{{source_name_part}}.obj",
    ]
    description = "assemble {{source}}"
  }

  tool("cc") {
    precompiled_header_type = "msvc"
    pdbname = "{{target_out_dir}}/{{label_name}}_c.pdb"

    # Label names may have spaces so pdbname must be quoted.
    command = "$env_setup $cc_wrapper $cl /nologo /showIncludes /FC {{defines}} {{include_dirs}} {{cflags}} $cl_m32_flag {{cflags_c}} /c {{source}} /Fo{{output}} /Fd\"$pdbname\""
    depsformat = "msvc"
    outputs = [
      "{{source_out_dir}}/{{target_output_name}}.{{source_name_part}}.obj",
    ]
    description = "compile {{source}}"
  }

  tool("cxx") {
    precompiled_header_type = "msvc"
    pdbname = "{{target_out_dir}}/{{label_name}}_c.pdb"

    # Label names may have spaces so pdbname must be quoted.
    command = "$env_setup $cc_wrapper $cl /nologo /showIncludes /FC {{defines}} {{include_dirs}} {{cflags}} $cl_m32_flag {{cflags_cc}} /c {{source}} /Fo{{output}} /Fd\"$pdbname\""
    depsformat = "msvc"
    outputs = [
      "{{source_out_dir}}/{{target_output_name}}.{{source_name_part}}.obj",
    ]
    description = "compile {{source}}"
  }

  tool("alink") {
    rspfile = "{{output}}.rsp"

    command = "$env_setup $lib /nologo /ignore:4221 {{arflags}} /OUT:{{output}} @$rspfile"
    outputs = [
      # Ignore {{output_extension}} and always use .lib, there's no reason to
      # allow targets to override this extension on Windows.
      "{{root_out_dir}}/{{target_output_name}}{{output_extension}}",
    ]
    default_output_extension = ".lib"
    default_output_dir = "{{target_out_dir}}"

    # inputs_newline works around a fixed per-line buffer size in the linker.
    rspfile_content = "{{inputs_newline}}"
    description = "link {{output}}"
  }

  tool("solink") {
    dllname = "{{output_dir}}/{{target_output_name}}{{output_extension}}"
    libname = "${dllname}.lib"
    pdbname = "${dllname}.pdb"
    rspfile = "${dllname}.rsp"

    command = "$env_setup $link /nologo /IMPLIB:$libname /DLL /OUT:$dllname /PDB:$pdbname @$rspfile"
    outputs = [
      dllname,
      libname,
      pdbname,
    ]
    default_output_extension = ".dll"
    default_output_dir = "{{root_out_dir}}"

    link_output = libname
    depend_output = libname
    runtime_outputs = [
      dllname,
      pdbname,
    ]

    # I don't quite understand this.  Aping Chrome's toolchain/win/BUILD.gn.
    restat = true

    # inputs_newline works around a fixed per-line buffer size in the linker.
    rspfile_content = "{{inputs_newline}} {{libs}} {{solibs}} {{ldflags}}"
    description = "link {{output}}"
  }

  tool("link") {
    exename = "{{root_out_dir}}/{{target_output_name}}{{output_extension}}"
    pdbname = "$exename.pdb"
    rspfile = "$exename.rsp"

    command = "$env_setup $link /nologo /OUT:$exename /PDB:$pdbname @$rspfile"
    default_output_extension = ".exe"
    default_output_dir = "{{root_out_dir}}"
    outputs = [
      exename,
    ]

    # inputs_newline works around a fixed per-line buffer size in the linker.
    rspfile_content = "{{inputs_newline}} {{libs}} {{solibs}} {{ldflags}}"
    description = "link {{output}}"
  }

  tool("stamp") {
    command = "$stamp {{output}}"
    description = "stamp {{output}}"
  }

  tool("copy") {
    cp_py = rebase_path("../cp.py")
    command = "python $cp_py {{source}} {{output}}"
    description = "copy {{source}} {{output}}"
  }
}

template("gcc_like_toolchain") {
  toolchain(target_name) {
    ar = invoker.ar
    cc = invoker.cc
    cxx = invoker.cxx
    lib_switch = "-l"
    lib_dir_switch = "-L"

    tool("cc") {
      depfile = "{{output}}.d"
      command = "$cc_wrapper $cc -MD -MF $depfile {{defines}} {{include_dirs}} {{cflags}} {{cflags_c}} -c {{source}} -o {{output}}"
      depsformat = "gcc"
      outputs = [
        "{{source_out_dir}}/{{target_output_name}}.{{source_name_part}}.o",
      ]
      description = "compile {{source}}"
    }

    tool("cxx") {
      depfile = "{{output}}.d"
      command = "$cc_wrapper $cxx -MD -MF $depfile {{defines}} {{include_dirs}} {{cflags}} {{cflags_cc}} -c {{source}} -o {{output}}"
      depsformat = "gcc"
      outputs = [
        "{{source_out_dir}}/{{target_output_name}}.{{source_name_part}}.o",
      ]
      description = "compile {{source}}"
    }

    tool("objc") {
      depfile = "{{output}}.d"
      command = "$cc_wrapper $cc -MD -MF $depfile {{defines}} {{include_dirs}} {{cflags}} {{cflags_objc}} -c {{source}} -o {{output}}"
      depsformat = "gcc"
      outputs = [
        "{{source_out_dir}}/{{target_output_name}}.{{source_name_part}}.o",
      ]
      description = "compile {{source}}"
    }

    tool("objcxx") {
      depfile = "{{output}}.d"
      command = "$cc_wrapper $cxx -MD -MF $depfile {{defines}} {{include_dirs}} {{cflags}} {{cflags_cc}} {{cflags_objcc}} -c {{source}} -o {{output}}"
      depsformat = "gcc"
      outputs = [
        "{{source_out_dir}}/{{target_output_name}}.{{source_name_part}}.o",
      ]
      description = "compile {{source}}"
    }

    tool("asm") {
      depfile = "{{output}}.d"
      command = "$cc_wrapper $cc -MD -MF $depfile {{defines}} {{include_dirs}} {{asmflags}} -c {{source}} -o {{output}}"
      depsformat = "gcc"
      outputs = [
        "{{source_out_dir}}/{{target_output_name}}.{{source_name_part}}.o",
      ]
      description = "assemble {{source}}"
    }

    tool("alink") {
      rspfile = "{{output}}.rsp"
      rspfile_content = "{{inputs}}"
      ar_py = rebase_path("../ar.py")
      command = "python $ar_py $ar {{output}} $rspfile"
      outputs = [
        "{{root_out_dir}}/{{target_output_name}}{{output_extension}}",
      ]
      default_output_extension = ".a"
      output_prefix = "lib"
      description = "link {{output}}"
    }

    tool("solink") {
      soname = "{{target_output_name}}{{output_extension}}"

      rpath = "-Wl,-soname,$soname"
      if (is_mac || is_ios) {
        rpath = "-Wl,-install_name,@rpath/$soname"
      }

      rspfile = "{{output}}.rsp"
      rspfile_content = "{{inputs}}"

      # --start-group/--end-group let us link multiple .a {{inputs}}
      # without worrying about their relative order on the link line.
      #
      # This is mostly important for traditional linkers like GNU ld and Gold.
      # The Mac/iOS linker neither needs nor accepts these flags.
      # LLD doesn't need these flags, but accepts and ignores them.
      _start_group = "-Wl,--start-group"
      _end_group = "-Wl,--end-group"
      if (is_mac || is_ios) {
        _start_group = ""
        _end_group = ""
      }

      command = "$cxx -shared {{ldflags}} $_start_group @$rspfile {{solibs}} $_end_group {{libs}} $rpath -o {{output}}"
      outputs = [
        "{{root_out_dir}}/$soname",
      ]
      output_prefix = "lib"
      default_output_extension = ".so"
      description = "link {{output}}"
    }

    tool("link") {
      exe_name = "{{root_out_dir}}/{{target_output_name}}{{output_extension}}"
      rspfile = "$exe_name.rsp"
      rspfile_content = "{{inputs}}"

      # --start-group/--end-group let us link multiple .a {{inputs}}
      # without worrying about their relative order on the link line.
      #
      # This is mostly important for traditional linkers like GNU ld and Gold.
      # The Mac/iOS linker neither needs nor accepts these flags.
      # LLD doesn't need these flags, but accepts and ignores them.
      _start_group = "-Wl,--start-group"
      _end_group = "-Wl,--end-group"
      if (is_mac || is_ios) {
        _start_group = ""
        _end_group = ""
      }
      command = "$cxx {{ldflags}} $_start_group @$rspfile {{solibs}} $_end_group {{libs}} -o $exe_name"

      outputs = [
        "$exe_name",
      ]
      description = "link {{output}}"
    }

    tool("stamp") {
      command = "$stamp {{output}}"
      description = "stamp {{output}}"
    }

    tool("copy") {
      cp_py = rebase_path("../cp.py")
      command = "python $cp_py {{source}} {{output}}"
      description = "copy {{source}} {{output}}"
    }

    tool("copy_bundle_data") {
      cp_py = rebase_path("../cp.py")
      command = "python $cp_py {{source}} {{output}}"
      description = "copy_bundle_data {{source}} {{output}}"
    }

    # We don't currently have any xcasset files so make this a NOP
    tool("compile_xcassets") {
      command = "true"
      description = "compile_xcassets {{output}}"
    }

    toolchain_args = {
      current_cpu = invoker.cpu
      current_os = invoker.os
    }
  }
}

gcc_like_toolchain("gcc_like") {
  cpu = current_cpu
  os = current_os
  ar = target_ar
  cc = target_cc
  cxx = target_cxx
}

gcc_like_toolchain("gcc_like_host") {
  cpu = host_cpu
  os = host_os
  ar = host_ar
  cc = host_cc
  cxx = host_cxx
}