update and clean up cystdlib.py script

Tools/cystdlib.py

@@ -5,13 +5,14 @@ Execute the script either in the CPython 'Lib' directory or pass the
 option '--current-python' to compile the standard library of the running
 Python interpreter.
 
-Pass '--parallel' to get a parallel build.
+Pass '-j N' to get a parallel build with N processes.
 
 Usage example::
 
     $ python cystdlib.py --current-python build_ext -i
 """
 
+import os
 import sys
 from distutils.core import setup
 from Cython.Build import cythonize
@@ -78,6 +79,7 @@ del special_directives[:]  # currently unused
 def build_extensions(includes='**/*.py',
                      excludes=excludes+broken,
                      special_directives=special_directives,
+                     language_level=sys.version_info[0],
                      parallel=None):
     if isinstance(includes, str):
         includes = [includes]
@@ -97,21 +99,25 @@ def build_extensions(includes='**/*.py',
             cythonize(modules,
                 exclude=exclude_now,
                 exclude_failures=True,
-                language_level=pyver,
+                language_level=language_level,
                 compiler_directives=d,
                 nthreads=parallel,
                 ))
     return extensions
 
+
 def build(extensions):
     try:
-        setup(name = 'stuff', ext_modules = extensions)
-        return extensions, True
+        setup(ext_modules=extensions)
+        result = True
     except:
         import traceback
-        print('error building extensions %s' % ([ext.name for ext in extensions],))
+        print('error building extensions %s' % (
+            [ext.name for ext in extensions],))
         traceback.print_exc()
-        return extensions, False
+        result = False
+    return extensions, result
+
 
 def _build(args):
     sys_args, ext = args
@@ -119,31 +125,47 @@ def _build(args):
     return build([ext])
 
 
+def parse_args():
+    from optparse import OptionParser
+    parser = OptionParser('%prog [options] [LIB_DIR (default: ./Lib)]')
+    parser.add_option(
+        '--current-python', dest='current_python', action='store_true',
+        help='compile the stdlib of the running Python')
+    parser.add_option(
+        '-j', '--jobs', dest='parallel_jobs', metavar='N',
+        type=int, default=1,
+        help='run builds in N parallel jobs (default: 1)')
+    options, args = parser.parse_args()
+    if not args:
+        args = ['./Lib']
+    elif len(args) > 1:
+        parser.error('only one argument expected, got %d' % len(args))
+    return options, args
+
+
 if __name__ == '__main__':
-    import sys
-    pyver = sys.version_info[0]
-    try:
-        sys.argv.remove('--current-python')
-    except ValueError:
-        pass
-    else:
+    options, args = parse_args()
+    if options.current_python:
         # assume that the stdlib is where the "os" module lives
-        import os
         os.chdir(os.path.dirname(os.__file__))
-
-    try:
-        sys.argv.remove('--parallel')
-        import multiprocessing
-        parallel_compiles = multiprocessing.cpu_count() * 2
-        print("Building in %d parallel processes" % parallel_compiles)
-    except (ValueError, ImportError):
-        parallel_compiles = None
-
-    extensions = build_extensions(parallel=parallel_compiles)
-    if parallel_compiles:
-        pool = multiprocessing.Pool(parallel_compiles)
-        sys_args = sys.argv[1:]
-        results = pool.map(_build, [ (sys_args, ext) for ext in extensions ])
+    else:
+        os.chdir(args[0])
+
+    pool = None
+    parallel_jobs = options.parallel_jobs
+    if options.parallel_jobs:
+        try:
+            import multiprocessing
+            pool = multiprocessing.Pool(parallel_jobs)
+            print("Building in %d parallel processes" % parallel_jobs)
+        except (ImportError, OSError):
+            print("Not building in parallel")
+            parallel_jobs = 0
+
+    extensions = build_extensions(parallel=parallel_jobs)
+    if pool is not None:
+        sys_args = ['-i']
+        results = pool.map(_build, [(sys_args, ext) for ext in extensions])
         pool.close()
         pool.join()
         for ext, result in results: