astrofrog · Jun 18, 2018 · Feb 22, 2018 · Jun 4, 2018 · bsipocz · May 25, 2018
diff --git a/.travis.yml b/.travis.yml
@@ -36,6 +36,24 @@ matrix:
       env: PYTHON_VERSION=3.6 PIP_DEPENDENCIES='git+https://github.com/sphinx-doc/sphinx.git#egg=sphinx coveralls'
            CONDA_DEPENDENCIES="setuptools cython numpy pytest-cov"
 
+    # Test conda's clang
+    - os: osx
+      env:
+        - PYTHON_VERSION=3.5
+        - CONDA_DEPENDENCIES="setuptools sphinx cython numpy pytest-cov clang llvm-openmp"
+      before_install:
+        - export TEST_OPENMP="True"
+        - export CC=clang
+
+    # Test gcc on OSX
+    - os: osx
+      env:
+        - PYTHON_VERSION=3.5
+        - CONDA_DEPENDENCIES="setuptools sphinx cython numpy pytest-cov gcc"
+      before_install:
+        - export TEST_OPENMP="True"
+        - export CC=gcc
+
   # Uncomment the following if there are issues in setuptools that we
   # can't work around quickly - otherwise leave uncommented so that
   # we notice when things go wrong.
@@ -45,6 +63,16 @@ matrix:
   #          CONDA_DEPENDENCIES='sphinx cython numpy pytest-cov'
   #          EVENT_TYPE='push pull_request cron'
 
+before_install:
+
+      # Test OSX without OpenMP support
+      # Since the matrix OSX tests use the OS shipped version of clang, they double up
+      # as exploratory tests for when the shipped version has automatic OpenMP support.
+      # These tests will then fail and at such a time a new one should be added
+      # to explicitly remove OpenMP support.
+    - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then export TEST_OPENMP="False";
+      else export TEST_OPENMP="True"; fi
+
 install:
 
     - git clone git://github.com/astropy/ci-helpers.git

diff --git a/CHANGES.rst b/CHANGES.rst
@@ -12,6 +12,13 @@ astropy-helpers Changelog
   by the ``sphinx-astropy`` package in conjunction with the ``astropy-theme-sphinx``,
   ``sphinx-automodapi``, and ``numpydoc`` packages. [#368]
 
+- openmp_helpers.py: Make add_openmp_flags_if_available() work for clang.
+  The necessary include, library, and runtime paths now get added to the C test code
+  used to determine if openmp works.
+  Autogenerator utility added ``openmp_enabled.is_openmp_enabled()``
+  which can be called post build to determine state of OpenMP support.
+  [#382]
+
 
 3.0.2 (unreleased)
 ------------------

diff --git a/astropy_helpers/openmp_helpers.py b/astropy_helpers/openmp_helpers.py
@@ -16,12 +16,14 @@
 import os
 import sys
 import glob
+import time
+import datetime
 import tempfile
 import subprocess
 
 from distutils import log
 from distutils.ccompiler import new_compiler
-from distutils.sysconfig import customize_compiler
+from distutils.sysconfig import customize_compiler, get_config_var
 from distutils.errors import CompileError, LinkError
 
 from .setup_helpers import get_compiler_option
@@ -39,69 +41,223 @@
 }
 """
 
+def _get_flag_value_from_var(flag, var, delim=' '):
+    """
+    Utility to extract ``flag`` value from `os.environ[``var``]` or, if not present,
+    from `distutils.sysconfig.get_config_var(``var``)`.
+    E.g. to get include path: _get_flag_value_from_var('-I', 'CFLAGS')
+    might return "/usr/local/include".
 
-def add_openmp_flags_if_available(extension):
+    Notes
+    -----
+    Not yet tested and therefore not yet supported on Windows
     """
-    Add OpenMP compilation flags, if available (if not a warning will be
-    printed to the console and no flags will be added)
 
-    Returns `True` if the flags were added, `False` otherwise.
+    if sys.platform.startswith('win'):
+        return None
+
+    # Simple input validation
+    if not var or not flag:
+        return None
+    flag_length = len(flag)
+    if not flag_length:
+        return None
+
+    # Look for var in os.eviron
+    try:
+        flags = os.environ[var]
+    except KeyError:
+        flags = None
+
+    # If os.environ was unsuccesful try in sysconfig
+    if not flags:
+        try:
+            flags = get_config_var(var)
+        except KeyError:
+            return None
+
+    # Extract flag from {var:value}
+    if flags:
+        for item in flags.split(delim):
+            if flag in item[:flag_length]:
+                return item[flag_length:]
+
+    return None
+
+def _get_include_path():
+    return _get_flag_value_from_var('-I', 'CFLAGS')
+
+def _get_library_path():
+    return _get_flag_value_from_var('-L', 'LDFLAGS')
+
+def get_openmp_flags():
     """
+    Utility for returning compiler and linker flags possibly needed for
+    OpenMP support.
 
-    ccompiler = new_compiler()
-    customize_compiler(ccompiler)
+    Returns
+    -------
+    result : `{'compiler_flags':<flags>, 'linker_flags':<flags>}`
 
-    tmp_dir = tempfile.mkdtemp()
+    Notes
+    -----
+    The flags returned are not tested for validity, use
+    `check_openmp_support(openmp_flags=get_openmp_flags())` to do so.
+    """
 
-    start_dir = os.path.abspath('.')
+    compile_flags = []
+    include_path = _get_include_path()
+    if include_path:
+        compile_flags.append('-I' + include_path)
+
+    link_flags = []
+    lib_path = _get_library_path()
+    if lib_path:
+        link_flags.append('-L' + lib_path)
 
     if get_compiler_option() == 'msvc':
-        compile_flag = '-openmp'
-        link_flag = ''
+        compile_flags.append('-openmp')
     else:
-        compile_flag = '-fopenmp'
-        link_flag = '-fopenmp'
+        compile_flags.append('-fopenmp')
+        link_flags.append('-fopenmp')
+        if lib_path:
+            link_flags.append('-Wl,-rpath,' + lib_path)
 
-    try:
+    return {'compiler_flags':compile_flags, 'linker_flags':link_flags}
+
+def check_openmp_support(openmp_flags=None):
+    """
+    Compile and run OpenMP test code to determine viable support.
+
+    Parameters
+    ----------
+    openmp_flags : dictionary, optional
+        Expecting `{'compiler_flags':<flags>, 'linker_flags':<flags>}`.
+        These are passed as `extra_postargs` to `compile()` and
+        `link_executable()` respectively.
+
+    Returns
+    -------
+    result : bool
+        `True` if the test passed, `False` otherwise.
+    """
+
+    ccompiler = new_compiler()
+    customize_compiler(ccompiler)
+
+    if not openmp_flags:
+        # customize_compiler() extracts info from os.environ. If certain keys
+        # exist it uses these plus those from sysconfig.get_config_vars().
+        # If the key is missing in os.environ it is not extracted from 
+        # sysconfig.get_config_var(). E.g. 'LDFLAGS' get left out, preventing
+        # clang from finding libomp.dylib because -L<path> is not passed to linker.
+        # Call get_openmp_flags() to get flags missed by customize_compiler().
+        openmp_flags = get_openmp_flags()
+    compile_flags = openmp_flags['compiler_flags'] if 'compiler_flags' in openmp_flags else None
+    link_flags = openmp_flags['linker_flags'] if 'linker_flags' in openmp_flags else None
 
+    tmp_dir = tempfile.mkdtemp()
+    start_dir = os.path.abspath('.')
+
+    try:
         os.chdir(tmp_dir)
 
+        # Write test program
         with open('test_openmp.c', 'w') as f:
             f.write(CCODE)
 
         os.mkdir('objects')
 
         # Compile, link, and run test program
-        ccompiler.compile(['test_openmp.c'], output_dir='objects', extra_postargs=[compile_flag])
-        ccompiler.link_executable(glob.glob(os.path.join('objects', '*' + ccompiler.obj_extension)), 'test_openmp', extra_postargs=[link_flag])
+        ccompiler.compile(['test_openmp.c'], output_dir='objects', extra_postargs=compile_flags)
+        ccompiler.link_executable(glob.glob(os.path.join('objects', '*' + ccompiler.obj_extension)), 'test_openmp', extra_postargs=link_flags)
         output = subprocess.check_output('./test_openmp').decode(sys.stdout.encoding or 'utf-8').splitlines()
 
         if 'nthreads=' in output[0]:
             nthreads = int(output[0].strip().split('=')[1])
             if len(output) == nthreads:
-                using_openmp = True
+                is_openmp_supported = True
             else:
                 log.warn("Unexpected number of lines from output of test OpenMP "
                          "program (output was {0})".format(output))
-                using_openmp = False
+                is_openmp_supported = False
         else:
             log.warn("Unexpected output from test OpenMP "
                      "program (output was {0})".format(output))
-            using_openmp = False
-
+            is_openmp_supported = False
     except (CompileError, LinkError):
-
-        using_openmp = False
+        is_openmp_supported = False
 
     finally:
-
         os.chdir(start_dir)
+
+    return is_openmp_supported
+
+def is_openmp_supported():
+    """
+    Utility to determine whether the build compiler
+    has OpenMP support.
+    """
+
+    # don't log
+    log_threshold = log.set_threshold(log.FATAL)
+    ret = check_openmp_support()
+    log.set_threshold(log_threshold)
+    return ret
+
+def add_openmp_flags_if_available(extension):
+    """
+    Add OpenMP compilation flags, if supported (if not a warning will be
+    printed to the console and no flags will be added.)
+
+    Returns `True` if the flags were added, `False` otherwise.
+    """
+
+    openmp_flags = get_openmp_flags()
+    using_openmp = check_openmp_support(openmp_flags=openmp_flags)
 
     if using_openmp:
-        log.info("Compiling Cython extension with OpenMP support")
-        extension.extra_compile_args.append(compile_flag)
-        extension.extra_link_args.append(link_flag)
+        compile_flags = openmp_flags['compiler_flags'] if 'compiler_flags' in openmp_flags else None
+        link_flags = openmp_flags['linker_flags'] if 'linker_flags' in openmp_flags else None
+        log.info("Compiling Cython/C/C++ extension with OpenMP support")
+        extension.extra_compile_args.extend(compile_flags)
+        extension.extra_link_args.extend(link_flags)
     else:
         log.warn("Cannot compile Cython extension with OpenMP, reverting to non-parallel code")
 
     return using_openmp
+
+_IS_OPENMP_ENABLED_SRC = """
+# Autogenerated by {packagetitle}'s setup.py on {timestamp!s}
+
+def is_openmp_enabled():
+    \'\'\'
+    Autogenerated utility to determine, post build, whether the package
+    was built with or without OpenMP support.
+    \'\'\'
+    return {return_bool}
+"""[1:]
+
+def generate_openmp_enabled_py(packagename, srcdir='.'):
+    """
+    Utility for creating `openmp_enabled.is_openmp_enabled()`
+    used to determine, post build, whether the package was built
+    with or without OpenMP support.
+    """
+
+    if packagename.lower() == 'astropy':
+        packagetitle = 'Astropy'
+    else:
+        packagetitle = packagename
+
+    epoch = int(os.environ.get('SOURCE_DATE_EPOCH', time.time()))
+    timestamp = datetime.datetime.utcfromtimestamp(epoch)
+
+    src = _IS_OPENMP_ENABLED_SRC.format(packagetitle=packagetitle,
+                                        timestamp=timestamp,
+                                        return_bool=is_openmp_supported())
+
+    package_srcdir = os.path.join(srcdir, *packagename.split('.'))
+    is_openmp_enabled_py = os.path.join(package_srcdir, 'openmp_enabled.py')
+    with open(is_openmp_enabled_py, 'w') as f:
+        f.write(src)
diff --git a/astropy_helpers/tests/test_openmp_helpers.py b/astropy_helpers/tests/test_openmp_helpers.py
@@ -3,15 +3,23 @@
 from copy import deepcopy
 from distutils.core import Extension
 
-from ..openmp_helpers import add_openmp_flags_if_available
+from ..openmp_helpers import add_openmp_flags_if_available, generate_openmp_enabled_py
 from ..setup_helpers import _module_state, register_commands
 
 IS_TRAVIS_LINUX = os.environ.get('TRAVIS_OS_NAME', None) == 'linux'
+IS_TRAVIS_OSX = os.environ.get('TRAVIS_OS_NAME', None) == 'osx'
 IS_APPVEYOR = os.environ.get('APPVEYOR', None) == 'True'
 PY3_LT_35 = sys.version_info[0] == 3 and sys.version_info[1] < 5
 
 _state = None
 
+try:
+    TEST_OPENMP = 'True' == os.environ['TEST_OPENMP']
+except KeyError:
+    if IS_APPVEYOR:
+        TEST_OPENMP = True
+    else:
+        raise
 
 def setup_function(function):
     global state
@@ -34,5 +42,37 @@ def test_add_openmp_flags_if_available():
     # Having this is useful because we'll find out if OpenMP no longer works
     # for any reason on platforms on which it does work at the time of writing.
     # OpenMP doesn't work on Python 3.x where x<5 on AppVeyor though.
-    if IS_TRAVIS_LINUX or (IS_APPVEYOR and not PY3_LT_35):
-        assert using_openmp
+    if IS_TRAVIS_LINUX or IS_TRAVIS_OSX or (IS_APPVEYOR and not PY3_LT_35):
+        if TEST_OPENMP:
+            assert using_openmp
+        else:
+            assert not using_openmp
+
+def test_generate_openmp_enabled_py():
+
+    register_commands('openmp_autogeneration_testing', '0.0', False)
+
+    # Test file generation
+    generate_openmp_enabled_py('')
+    assert os.path.isfile('openmp_enabled.py')
+
+    with open('openmp_enabled.py', 'r') as fid:
+        contents = fid.read()
+    print(contents)
+
+    # Travis OSX tests experience an unstable module import error.
+    # Sometimes finding and importing the module, `openmp_enabled`,
+    # more often not. Adding '.' to the path seems to stabilize the
+    # issue, even though it should not be needed.
+    sys.path.append('.')
+    from openmp_enabled import is_openmp_enabled
+
+    is_openmp_enabled = is_openmp_enabled()
+
+    # Test is_openmp_enabled()
+    assert isinstance(is_openmp_enabled, bool)
+
+    if TEST_OPENMP:
+        assert is_openmp_enabled
+    else:
+        assert not is_openmp_enabled