[build support] Generic prefixed binary lookup function in swift_build_support

utils/build-script

@@ -39,13 +39,14 @@ from SwiftBuildSupport import (
 
 sys.path.append(os.path.join(os.path.dirname(__file__), 'swift_build_support'))
 
-import swift_build_support.clang    # noqa (E402 module level import not at top of file)
-import swift_build_support.cmake    # noqa (E402)
-import swift_build_support.debug    # noqa (E402)
+# E402 means module level import not at top of file
+import swift_build_support.toolchain  # noqa (E402)
+import swift_build_support.cmake      # noqa (E402)
+import swift_build_support.debug      # noqa (E402)
 from swift_build_support.migration import migrate_impl_args  # noqa (E402)
-import swift_build_support.ninja    # noqa (E402)
-import swift_build_support.tar      # noqa (E402)
-import swift_build_support.targets  # noqa (E402)
+import swift_build_support.ninja      # noqa (E402)
+import swift_build_support.tar        # noqa (E402)
+import swift_build_support.targets    # noqa (E402)
 
 
 # Main entry point for the preset mode.
@@ -1018,7 +1019,7 @@ the number of parallel build jobs to use""",
     if args.clean and os.path.isdir(build_dir):
         shutil.rmtree(build_dir)
 
-    host_clang = swift_build_support.clang.host_clang(
+    host_clang = swift_build_support.toolchain.host_clang(
         xcrun_toolchain=args.darwin_xcrun_toolchain)
     if not host_clang:
         print_with_argv0(

utils/swift_build_support/swift_build_support/toolchain.py

@@ -0,0 +1,131 @@
+# -*- python -*-
+# swift_build_support/toolchain.py - Detect host machine's versioned
+# executables
+#
+# This source file is part of the Swift.org open source project
+#
+# Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
+# Licensed under Apache License v2.0 with Runtime Library Exception
+#
+# See http://swift.org/LICENSE.txt for license information
+# See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+#
+# ----------------------------------------------------------------------------
+#
+# Find the path to a Clang executable on the host machine that is most
+# suitable for building Swift.
+#
+# ----------------------------------------------------------------------------
+
+from __future__ import absolute_import
+
+import platform
+import subprocess
+
+from . import xcrun
+from .which import which
+
+
+class Toolchain(object):
+    """
+    A class that stores accessible paths to system commands.
+
+    It requires a 'cc' and 'cxx' tool in its keyword args.
+    """
+    def __init__(self, cc=None, cxx=None, **kwargs):
+        self.cc = cc
+        self.cxx = cxx
+        self.tools = [cc, cxx]
+        for tool, path in kwargs.iteritems():
+            self.tools.append(path)
+            setattr(self, tool, path)
+
+
+def _freebsd_release_date():
+    """
+    Return the release date for FreeBSD operating system on this host.
+    If the release date cannot be ascertained, return None.
+    """
+    try:
+        # For details on `sysctl`, see:
+        # http://www.freebsd.org/cgi/man.cgi?sysctl(8)
+        return int(subprocess.check_output(
+            ['sysctl', '-n', 'kern.osreldate']).rstrip())
+    except subprocess.CalledProcessError:
+        return None
+
+
+def _first_common_toolchain(tools, suffixes=None):
+    """
+    Return a Toolchain of resolved paths where each path has
+    the same suffix.
+
+    If there is no common version of all binaries found, return None.
+    """
+    if suffixes is None:
+        # No suffixes provided, default to using empty suffix only
+        suffixes = ['']
+
+    for suffix in suffixes:
+        path_map = dict()
+        for name, tool in tools.iteritems():
+            path = which(tool + suffix)
+            if not path:
+                break
+            path_map[name] = path
+        if len(path_map) == len(tools):
+            return Toolchain(**path_map)
+    return None
+
+
+def host_toolchain(xcrun_toolchain='default', tools=None, suffixes=None):
+    """
+    Return a Toolchain with the first available versions of all
+    specified tools, plus clang and clang++, searching in the order of the
+    given suffixes.
+
+    If no matching executables are found, return None.
+    """
+    if tools is None:
+        tools = dict()
+
+    # Require cc and cxx for a toolchain; this ensures whatever llvm tool we
+    # find matches the version of clang returned by a previous run of
+    # this tool
+    tools['cc'] = 'clang'
+    tools['cxx'] = 'clang++'
+
+    if platform.system() == 'Darwin':
+        # Only use xcrun on Darwin
+        path_map = {}
+        for name, tool in tools.iteritems():
+            path = xcrun.find(xcrun_toolchain, tool)
+            if not path:
+                return None
+            path_map[name] = path
+        return Toolchain(**path_map)
+    else:
+        return _first_common_toolchain(tools, suffixes=suffixes)
+
+
+def host_clang(xcrun_toolchain):
+    """
+    Return a Toolchain for the host platform.
+    If no appropriate compilers can be found, return None.
+    """
+    if platform.system() == 'FreeBSD':
+        # See: https://github.com/apple/swift/pull/169
+        # Building Swift from source requires a recent version of the Clang
+        # compiler with C++14 support.
+        freebsd_release_date = _freebsd_release_date()
+        if freebsd_release_date and freebsd_release_date >= 1100000:
+            # On newer releases of FreeBSD, the default Clang is sufficient.
+            return host_toolchain(xcrun_toolchain)
+        else:
+            # On older releases, or on releases for which we cannot determine
+            # the release date, we search for the most modern version
+            # available.
+            return host_toolchain(xcrun_toolchain,
+                                  suffixes=['38', '37', '36', '35'])
+    return host_toolchain(xcrun_toolchain,
+                          suffixes=['-3.8', '-3.7', '-3.6', '-3.5'])

utils/swift_build_support/tests/test_toolchain.py

@@ -0,0 +1,62 @@
+# -*- python -*-
+# test_toolchain.py - Unit tests for swift_build_support.toolchain
+#
+# This source file is part of the Swift.org open source project
+#
+# Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
+# Licensed under Apache License v2.0 with Runtime Library Exception
+#
+# See http://swift.org/LICENSE.txt for license information
+# See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+
+import os
+import platform
+import unittest
+
+from swift_build_support.toolchain import host_clang, host_toolchain
+
+
+class HostClangTestCase(unittest.TestCase):
+    def test_clang_available_on_this_platform(self):
+        # Test that Clang is installed on this platform, as a means of
+        # testing host_clang().
+        clang = host_clang(xcrun_toolchain='default')
+
+        # The CC and CXX from host_clang() should be of the form
+        # 'path/to/clang', where 'clang' may have a trailing version
+        # number.
+        self.assertTrue(os.path.split(clang.cc)[-1].startswith('clang'))
+        self.assertTrue(os.path.split(clang.cxx)[-1].startswith('clang++'))
+
+
+class HostToolchainTestCase(unittest.TestCase):
+    def test_found_executables_match(self):
+        # Test that the raw incovation of _first_common_executables
+        # either returns None or matching paths.
+        suffixes = ['', '-3.8', '-3.7', '-3.6']
+        toolchain = host_toolchain(suffixes=suffixes)
+        self.assertTrue(len(toolchain.tools) == 2)
+
+        exec_names = {'foo': 'a-tool-that-does-not-exist'}
+        toolchain = host_toolchain(tools=exec_names,
+                                   suffixes=suffixes)
+        self.assertIsNone(toolchain)
+
+    @unittest.skipUnless(platform.system() == 'Darwin',
+                         'llvm-cov is only guaranteed to exist on OS X')
+    def test_can_find_llvm_cov(self):
+        suffixes = ['', '-3.8', '-3.7', '-3.6']
+        exec_names = {'llvm_cov': 'llvm-cov'}
+        toolchain = host_toolchain(tools=exec_names, suffixes=suffixes)
+
+        # must have clang, clang++, and llvm-cov
+        self.assertTrue(len(toolchain.tools) == 3)
+
+        try:
+            toolchain.llvm_cov
+        except AttributeError:
+            self.fail("toolchain does not have llvm_cov")
+
+
+if __name__ == '__main__':
+    unittest.main()