class Gcc < Formula
  desc "GNU compiler collection"
  homepage "https://gcc.gnu.org/"
  url "https://ftp.gnu.org/gnu/gcc/gcc-10.2.0/gcc-10.2.0.tar.xz"
  mirror "https://ftpmirror.gnu.org/gcc/gcc-10.2.0/gcc-10.2.0.tar.xz"
  sha256 "b8dd4368bb9c7f0b98188317ee0254dd8cc99d1e3a18d0ff146c855fe16c1d8c"
  license "GPL-3.0"
  head "https://gcc.gnu.org/git/gcc.git"

  bottle do
    sha256 "8dbccea194c20b1037b7e8180986e98a8ee3e37eaac12c7d223c89be3deaac6a" => :catalina
    sha256 "79d2293ce912dc46af961f30927b31eb06844292927be497015496f79ac41557" => :mojave
    sha256 "5ed870a39571614dc5d83be26d73a4164911f4356b80d9345258a4c1dc3f1b70" => :high_sierra
  end

  # The bottles are built on systems with the CLT installed, and do not work
  # out of the box on Xcode-only systems due to an incorrect sysroot.
  pour_bottle? do
    reason "The bottle needs the Xcode CLT to be installed."
    satisfy { MacOS::CLT.installed? }
  end

  depends_on "gmp"
  depends_on "isl"
  depends_on "libmpc"
  depends_on "mpfr"

  uses_from_macos "zlib"

  # GCC bootstraps itself, so it is OK to have an incompatible C++ stdlib
  cxxstdlib_check :skip

  def version_suffix
    if build.head?
      "HEAD"
    else
      version.to_s.slice(/\d+/)
    end
  end

  def install
    # GCC will suffer build errors if forced to use a particular linker.
    ENV.delete "LD"

    # We avoiding building:
    #  - Ada, which requires a pre-existing GCC Ada compiler to bootstrap
    #  - Go, currently not supported on macOS
    #  - BRIG
    languages = %w[c c++ objc obj-c++ fortran]

    osmajor = `uname -r`.split(".").first
    pkgversion = "Homebrew GCC #{pkg_version} #{build.used_options*" "}".strip

    args = %W[
      --build=x86_64-apple-darwin#{osmajor}
      --prefix=#{prefix}
      --libdir=#{lib}/gcc/#{version_suffix}
      --disable-nls
      --enable-checking=release
      --enable-languages=#{languages.join(",")}
      --program-suffix=-#{version_suffix}
      --with-gmp=#{Formula["gmp"].opt_prefix}
      --with-mpfr=#{Formula["mpfr"].opt_prefix}
      --with-mpc=#{Formula["libmpc"].opt_prefix}
      --with-isl=#{Formula["isl"].opt_prefix}
      --with-system-zlib
      --with-pkgversion=#{pkgversion}
      --with-bugurl=https://github.com/Homebrew/homebrew-core/issues
    ]

    # Xcode 10 dropped 32-bit support
    args << "--disable-multilib" if DevelopmentTools.clang_build_version >= 1000

    # System headers may not be in /usr/include
    sdk = MacOS.sdk_path_if_needed
    if sdk
      args << "--with-native-system-header-dir=/usr/include"
      args << "--with-sysroot=#{sdk}"
    end

    # Avoid reference to sed shim
    args << "SED=/usr/bin/sed"

    # Ensure correct install names when linking against libgcc_s;
    # see discussion in https://github.com/Homebrew/legacy-homebrew/pull/34303
    inreplace "libgcc/config/t-slibgcc-darwin", "@shlib_slibdir@", "#{HOMEBREW_PREFIX}/lib/gcc/#{version_suffix}"

    mkdir "build" do
      system "../configure", *args

      # Use -headerpad_max_install_names in the build,
      # otherwise updated load commands won't fit in the Mach-O header.
      # This is needed because `gcc` avoids the superenv shim.
      system "make", "BOOT_LDFLAGS=-Wl,-headerpad_max_install_names"
      system "make", "install"

      bin.install_symlink bin/"gfortran-#{version_suffix}" => "gfortran"
    end

    # Handle conflicts between GCC formulae and avoid interfering
    # with system compilers.
    # Rename man7.
    Dir.glob(man7/"*.7") { |file| add_suffix file, version_suffix }
    # Even when we disable building info pages some are still installed.
    info.rmtree
  end

  def add_suffix(file, suffix)
    dir = File.dirname(file)
    ext = File.extname(file)
    base = File.basename(file, ext)
    File.rename file, "#{dir}/#{base}-#{suffix}#{ext}"
  end

  test do
    (testpath/"hello-c.c").write <<~EOS
      #include <stdio.h>
      int main()
      {
        puts("Hello, world!");
        return 0;
      }
    EOS
    system "#{bin}/gcc-#{version_suffix}", "-o", "hello-c", "hello-c.c"
    assert_equal "Hello, world!\n", `./hello-c`

    (testpath/"hello-cc.cc").write <<~EOS
      #include <iostream>
      int main()
      {
        std::cout << "Hello, world!" << std::endl;
        return 0;
      }
    EOS
    system "#{bin}/g++-#{version_suffix}", "-o", "hello-cc", "hello-cc.cc"
    assert_equal "Hello, world!\n", `./hello-cc`

    (testpath/"test.f90").write <<~EOS
      integer,parameter::m=10000
      real::a(m), b(m)
      real::fact=0.5

      do concurrent (i=1:m)
        a(i) = a(i) + fact*b(i)
      end do
      write(*,"(A)") "Done"
      end
    EOS
    system "#{bin}/gfortran", "-o", "test", "test.f90"
    assert_equal "Done\n", `./test`
  end
end
