Adding basic Windows features (#21259)

* Snapshot of some MSVC infrastructure added during experiments a while ago.  Rebasing from spack/develop.

* Added platform and OS definitions for Windows.

* Updated Windows platform file to conform to new archspec use.

* Added Windows as a platform; introduced some debugging code.

* Added type annotations.

* Fixed copyright.

* Removed print statements.

* Ensure `spack arch` returns correctly on Windows (#21428)

* Correctly identify windows as 'windows-Windows10-AMD64'

6 files changed, 138 insertions, 3 deletions

diff --git a/lib/spack/env/cc b/lib/spack/env/cc
index 1a52f2c612..9fd0e4dfbc 100755
--- a/lib/spack/env/cc
+++ b/lib/spack/env/cc
@@ -241,7 +241,7 @@ case "$command" in
         mode=cpp
         debug_flags="-g"
         ;;
-    cc|c89|c99|gcc|clang|armclang|icc|icx|pgcc|nvc|xlc|xlc_r|fcc|amdclang)
+    cc|c89|c99|gcc|clang|armclang|icc|icx|pgcc|nvc|xlc|xlc_r|fcc|amdclang|cl.exe)
         command="$SPACK_CC"
         language="C"
         comp="CC"
diff --git a/lib/spack/llnl/util/tty/log.py b/lib/spack/llnl/util/tty/log.py
index 1a93b570a5..566d180645 100644
--- a/lib/spack/llnl/util/tty/log.py
+++ b/lib/spack/llnl/util/tty/log.py
@@ -564,7 +564,7 @@ class log_output(object):
         sys.stdout.flush()
         sys.stderr.flush()
 
-        # Now do the actual output rediction.
+        # Now do the actual output redirection.
         self.use_fds = _file_descriptors_work(sys.stdout, sys.stderr)
         if self.use_fds:
             # We try first to use OS-level file descriptors, as this
@@ -725,7 +725,8 @@ def _writer_daemon(stdin_multiprocess_fd, read_multiprocess_fd, write_fd, echo,
     # write_fd to terminate the reading loop, so we close the file descriptor
     # here. Forking is the process spawning method everywhere except Mac OS
     # for Python >= 3.8 and on Windows
-    if sys.version_info < (3, 8) or sys.platform != 'darwin':
+    if sys.version_info < (3, 8) \
+            or sys.platform not in ['darwin', 'cygwin']:
         os.close(write_fd)
 
     # Use line buffering (3rd param = 1) since Python 3 has a bug
diff --git a/lib/spack/spack/compilers/msvc.py b/lib/spack/spack/compilers/msvc.py
new file mode 100644
index 0000000000..ac5da84705
--- /dev/null
+++ b/lib/spack/spack/compilers/msvc.py
@@ -0,0 +1,35 @@
+# Copyright 2013-2020 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+from typing import List  # novm
+from spack.compiler import Compiler
+
+
+class Msvc(Compiler):
+    # Subclasses use possible names of C compiler
+    cc_names = ['cl.exe']
+
+    # Subclasses use possible names of C++ compiler
+    cxx_names = ['cl.exe']
+
+    # Subclasses use possible names of Fortran 77 compiler
+    f77_names = []  # type: List[str]
+
+    # Subclasses use possible names of Fortran 90 compiler
+    fc_names = []  # type: List[str]
+
+    # Named wrapper links within build_env_path
+    link_paths = {'cc': 'msvc/cl.exe',
+                  'cxx': 'msvc/cl.exe',
+                  'f77': '',
+                  'fc': ''}
+
+    @property
+    def verbose_flag(self):
+        return ""
+
+    @property
+    def pic_flag(self):
+        return ""
diff --git a/lib/spack/spack/operating_systems/windows_os.py b/lib/spack/spack/operating_systems/windows_os.py
new file mode 100755
index 0000000000..c4f8fa7f84
--- /dev/null
+++ b/lib/spack/spack/operating_systems/windows_os.py
@@ -0,0 +1,29 @@
+# Copyright 2013-2021 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+from spack.architecture import OperatingSystem
+from spack.version import Version
+
+
+# FIXME: To get the actual Windows version, we need a python that runs
+# natively on Windows, not Cygwin.
+def windows_version():
+    """temporary workaround to return a Windows version as a Version object
+    """
+    return Version('10')
+
+
+class WindowsOs(OperatingSystem):
+    """This class represents the Windows operating system.  This will be
+    auto detected using the python platform.win32_ver() once we have a
+    python setup that runs natively.  The Windows platform will be represented
+    using the major version operating system number, e.g. 10.
+    """
+
+    def __init__(self):
+        super(WindowsOs, self).__init__('Windows10', '10')
+
+    def __str__(self):
+        return self.name
diff --git a/lib/spack/spack/platforms/windows.py b/lib/spack/spack/platforms/windows.py
new file mode 100755
index 0000000000..7c9ed1443d
--- /dev/null
+++ b/lib/spack/spack/platforms/windows.py
@@ -0,0 +1,40 @@
+# Copyright 2013-2021 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+import platform
+
+import archspec.cpu
+
+from spack.architecture import Platform, Target
+from spack.operating_systems.windows_os import WindowsOs
+
+
+class Windows(Platform):
+    priority    = 101
+
+    # binary_formats = ['macho']
+
+    def __init__(self):
+        super(Windows, self).__init__('windows')
+
+        for name in archspec.cpu.TARGETS:
+            self.add_target(name, Target(name))
+
+        self.default = archspec.cpu.host().name
+        self.front_end = self.default
+        self.back_end = self.default
+
+        windows_os = WindowsOs()
+
+        self.default_os = str(windows_os)
+        self.front_os   = str(windows_os)
+        self.back_os    = str(windows_os)
+
+        self.add_operating_system(str(windows_os), windows_os)
+
+    @classmethod
+    def detect(cls):
+        plat = platform.system().lower()
+        return 'cygwin' in plat or 'win32' in plat or 'windows' in plat
diff --git a/lib/spack/spack/util/debug.py b/lib/spack/spack/util/debug.py
index 0cae1ef58a..8a15b76f16 100644
--- a/lib/spack/spack/util/debug.py
+++ b/lib/spack/spack/util/debug.py
@@ -13,6 +13,8 @@ import code
 import os
 import signal
 import traceback
+import sys
+import pdb
 
 
 def debug_handler(sig, frame):
@@ -32,3 +34,31 @@ def debug_handler(sig, frame):
 def register_interrupt_handler():
     """Print traceback and enter an interpreter on Ctrl-C"""
     signal.signal(signal.SIGINT, debug_handler)
+
+
+# Subclass of the debugger to keep readline working.  See
+# https://stackoverflow.com/questions/4716533/how-to-attach-debugger-to-a-python-subproccess/23654936
+class ForkablePdb(pdb.Pdb):
+
+    _original_stdin_fd = sys.stdin.fileno()
+    _original_stdin = None
+
+    def __init__(self, stdout_fd=None, stderr_fd=None):
+        pdb.Pdb.__init__(self, nosigint=True)
+        self._stdout_fd = stdout_fd
+        self._stderr_fd = stderr_fd
+
+    def _cmdloop(self):
+        current_stdin = sys.stdin
+        try:
+            if not self._original_stdin:
+                self._original_stdin = os.fdopen(self._original_stdin_fd)
+            sys.stdin = self._original_stdin
+            if self._stdout_fd is not None:
+                os.dup2(self._stdout_fd, sys.stdout.fileno())
+                os.dup2(self._stdout_fd, self.stdout.fileno())
+            if self._stderr_fd is not None:
+                os.dup2(self._stderr_fd, sys.stderr.fileno())
+            self.cmdloop()
+        finally:
+            sys.stdin = current_stdin