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Implements the Distutils 'build_ext' command, for building extension
modules (currently limited to C extensions, should accommodate C++
extensions ASAP)."""
import contextlib
import os
import re
import sys
from distutils.core import Command
from distutils.errors import *
from distutils.sysconfig import customize_compiler, get_python_version
from distutils.sysconfig import get_config_h_filename
from distutils.dep_util import newer_group
from distutils.extension import Extension
from distutils.util import get_platform
from distutils import log
from site import USER_BASE
# An extension name is just a dot-separated list of Python NAMEs (ie.
# the same as a fully-qualified module name).
extension_name_re = re.compile \
def show_compilers ():
from distutils.ccompiler import show_compilers
class build_ext(Command):
description = "build C/C++ extensions (compile/link to build directory)"
# XXX thoughts on how to deal with complex command-line options like
# these, i.e. how to make it so fancy_getopt can suck them off the
# command line and make it look like defined the appropriate
# lists of tuples of what-have-you.
# - each command needs a callback to process its command-line options
# - Command.__init__() needs access to its share of the whole
# command line (must ultimately come from
# Distribution.parse_command_line())
# - it then calls the current command class' option-parsing
# callback to deal with weird options like -D, which have to
# parse the option text and churn out some custom data
# structure
# - that data structure (in this case, a list of 2-tuples)
# will then be present in the command object by the time
# we get to finalize_options() (i.e. the constructor
# takes care of both command-line and client options
# in between initialize_options() and finalize_options())
sep_by = " (separated by '%s')" % os.pathsep
user_options = [
('build-lib=', 'b',
"directory for compiled extension modules"),
('build-temp=', 't',
"directory for temporary files (build by-products)"),
('plat-name=', 'p',
"platform name to cross-compile for, if supported "
"(default: %s)" % get_platform()),
('inplace', 'i',
"ignore build-lib and put compiled extensions into the source " +
"directory alongside your pure Python modules"),
('include-dirs=', 'I',
"list of directories to search for header files" + sep_by),
('define=', 'D',
"C preprocessor macros to define"),
('undef=', 'U',
"C preprocessor macros to undefine"),
('libraries=', 'l',
"external C libraries to link with"),
('library-dirs=', 'L',
"directories to search for external C libraries" + sep_by),
('rpath=', 'R',
"directories to search for shared C libraries at runtime"),
('link-objects=', 'O',
"extra explicit link objects to include in the link"),
('debug', 'g',
"compile/link with debugging information"),
('force', 'f',
"forcibly build everything (ignore file timestamps)"),
('compiler=', 'c',
"specify the compiler type"),
('parallel=', 'j',
"number of parallel build jobs"),
('swig-cpp', None,
"make SWIG create C++ files (default is C)"),
('swig-opts=', None,
"list of SWIG command line options"),
('swig=', None,
"path to the SWIG executable"),
('user', None,
"add user include, library and rpath")
boolean_options = ['inplace', 'debug', 'force', 'swig-cpp', 'user']
help_options = [
('help-compiler', None,
"list available compilers", show_compilers),
def initialize_options(self):
self.extensions = None
self.build_lib = None
self.plat_name = None
self.build_temp = None
self.inplace = 0
self.package = None
self.include_dirs = None
self.define = None
self.undef = None
self.libraries = None
self.library_dirs = None
self.rpath = None
self.link_objects = None
self.debug = None
self.force = None
self.compiler = None
self.swig = None
self.swig_cpp = None
self.swig_opts = None
self.user = None
self.parallel = None
def finalize_options(self):
from distutils import sysconfig
('build_lib', 'build_lib'),
('build_temp', 'build_temp'),
('compiler', 'compiler'),
('debug', 'debug'),
('force', 'force'),
('parallel', 'parallel'),
('plat_name', 'plat_name'),
if self.package is None:
self.package = self.distribution.ext_package
self.extensions = self.distribution.ext_modules
# Make sure Python's include directories (for Python.h, pyconfig.h,
# etc.) are in the include search path.
py_include = sysconfig.get_python_inc()
plat_py_include = sysconfig.get_python_inc(plat_specific=1)
if self.include_dirs is None:
self.include_dirs = self.distribution.include_dirs or []
if isinstance(self.include_dirs, str):
self.include_dirs = self.include_dirs.split(os.pathsep)
# If in a virtualenv, add its include directory
# Issue 16116
if sys.exec_prefix != sys.base_exec_prefix:
self.include_dirs.append(os.path.join(sys.exec_prefix, 'include'))
# Put the Python "system" include dir at the end, so that
# any local include dirs take precedence.
if plat_py_include != py_include:
# Life is easier if we're not forever checking for None, so
# simplify these options to empty lists if unset
if self.libraries is None:
self.libraries = []
if self.library_dirs is None:
self.library_dirs = []
elif isinstance(self.library_dirs, str):
self.library_dirs = self.library_dirs.split(os.pathsep)
if self.rpath is None:
self.rpath = []
elif isinstance(self.rpath, str):
self.rpath = self.rpath.split(os.pathsep)
# for extensions under windows use different directories
# for Release and Debug builds.
# also Python's library directory must be appended to library_dirs
if == 'nt':
# the 'libs' directory is for binary installs - we assume that
# must be the *native* platform. But we don't really support
# cross-compiling via a binary install anyway, so we let it go.
self.library_dirs.append(os.path.join(sys.exec_prefix, 'libs'))
if sys.base_exec_prefix != sys.prefix: # Issue 16116
self.library_dirs.append(os.path.join(sys.base_exec_prefix, 'libs'))
if self.debug:
self.build_temp = os.path.join(self.build_temp, "Debug")
self.build_temp = os.path.join(self.build_temp, "Release")
# Append the source distribution include and library directories,
# this allows distutils on windows to work in the source tree
_sys_home = getattr(sys, '_home', None)
if _sys_home:
# Use the .lib files for the correct architecture
if self.plat_name == 'win32':
suffix = 'win32'
# win-amd64
suffix = self.plat_name[4:]
new_lib = os.path.join(sys.exec_prefix, 'PCbuild')
if suffix:
new_lib = os.path.join(new_lib, suffix)
# For extensions under Cygwin, Python's library directory must be
# appended to library_dirs
if sys.platform[:6] == 'cygwin':
if sys.executable.startswith(os.path.join(sys.exec_prefix, "bin")):
# building third party extensions
self.library_dirs.append(os.path.join(sys.prefix, "lib",
"python" + get_python_version(),
# building python standard extensions
# For building extensions with a shared Python library,
# Python's library directory must be appended to library_dirs
# See Issues: #1600860, #4366
if (sysconfig.get_config_var('Py_ENABLE_SHARED')):
if not sysconfig.python_build:
# building third party extensions
# building python standard extensions
# The argument parsing will result in self.define being a string, but
# it has to be a list of 2-tuples. All the preprocessor symbols
# specified by the 'define' option will be set to '1'. Multiple
# symbols can be separated with commas.
if self.define:
defines = self.define.split(',')
self.define = [(symbol, '1') for symbol in defines]
# The option for macros to undefine is also a string from the
# option parsing, but has to be a list. Multiple symbols can also
# be separated with commas here.
if self.undef:
self.undef = self.undef.split(',')
if self.swig_opts is None:
self.swig_opts = []
self.swig_opts = self.swig_opts.split(' ')
# Finally add the user include and library directories if requested
if self.user:
user_include = os.path.join(USER_BASE, "include")
user_lib = os.path.join(USER_BASE, "lib")
if os.path.isdir(user_include):
if os.path.isdir(user_lib):
if isinstance(self.parallel, str):
self.parallel = int(self.parallel)
except ValueError:
raise DistutilsOptionError("parallel should be an integer")
def run(self):
from distutils.ccompiler import new_compiler
# 'self.extensions', as supplied by, is a list of
# Extension instances. See the documentation for Extension (in
# distutils.extension) for details.
# For backwards compatibility with Distutils 0.8.2 and earlier, we
# also allow the 'extensions' list to be a list of tuples:
# (ext_name, build_info)
# where build_info is a dictionary containing everything that
# Extension instances do except the name, with a few things being
# differently named. We convert these 2-tuples to Extension
# instances as needed.
if not self.extensions:
# If we were asked to build any C/C++ libraries, make sure that the
# directory where we put them is in the library search path for
# linking extensions.
if self.distribution.has_c_libraries():
build_clib = self.get_finalized_command('build_clib')
self.libraries.extend(build_clib.get_library_names() or [])
# Setup the CCompiler object that we'll use to do all the
# compiling and linking
self.compiler = new_compiler(compiler=self.compiler,
# If we are cross-compiling, init the compiler now (if we are not
# cross-compiling, init would not hurt, but people may rely on
# late initialization of compiler even if they shouldn't...)
if == 'nt' and self.plat_name != get_platform():
# And make sure that any compile/link-related options (which might
# come from the command-line or from the setup script) are set in
# that CCompiler object -- that way, they automatically apply to
# all compiling and linking done here.
if self.include_dirs is not None:
if self.define is not None:
# 'define' option is a list of (name,value) tuples
for (name, value) in self.define:
self.compiler.define_macro(name, value)
if self.undef is not None:
for macro in self.undef:
if self.libraries is not None:
if self.library_dirs is not None:
if self.rpath is not None:
if self.link_objects is not None:
# Now actually compile and link everything.
def check_extensions_list(self, extensions):
"""Ensure that the list of extensions (presumably provided as a
command option 'extensions') is valid, i.e. it is a list of
Extension objects. We also support the old-style list of 2-tuples,
where the tuples are (ext_name, build_info), which are converted to
Extension instances here.
Raise DistutilsSetupError if the structure is invalid anywhere;
just returns otherwise.
if not isinstance(extensions, list):
raise DistutilsSetupError(
"'ext_modules' option must be a list of Extension instances")
for i, ext in enumerate(extensions):
if isinstance(ext, Extension):
continue # OK! (assume type-checking done
# by Extension constructor)
if not isinstance(ext, tuple) or len(ext) != 2:
raise DistutilsSetupError(
"each element of 'ext_modules' option must be an "
"Extension instance or 2-tuple")
ext_name, build_info = ext
log.warn("old-style (ext_name, build_info) tuple found in "
"ext_modules for extension '%s' "
"-- please convert to Extension instance", ext_name)
if not (isinstance(ext_name, str) and
raise DistutilsSetupError(
"first element of each tuple in 'ext_modules' "
"must be the extension name (a string)")
if not isinstance(build_info, dict):
raise DistutilsSetupError(
"second element of each tuple in 'ext_modules' "
"must be a dictionary (build info)")
# OK, the (ext_name, build_info) dict is type-safe: convert it
# to an Extension instance.
ext = Extension(ext_name, build_info['sources'])
# Easy stuff: one-to-one mapping from dict elements to
# instance attributes.
for key in ('include_dirs', 'library_dirs', 'libraries',
'extra_objects', 'extra_compile_args',
val = build_info.get(key)
if val is not None:
setattr(ext, key, val)
# Medium-easy stuff: same syntax/semantics, different names.
ext.runtime_library_dirs = build_info.get('rpath')
if 'def_file' in build_info:
log.warn("'def_file' element of build info dict "
"no longer supported")
# Non-trivial stuff: 'macros' split into 'define_macros'
# and 'undef_macros'.
macros = build_info.get('macros')
if macros:
ext.define_macros = []
ext.undef_macros = []
for macro in macros:
if not (isinstance(macro, tuple) and len(macro) in (1, 2)):
raise DistutilsSetupError(
"'macros' element of build info dict "
"must be 1- or 2-tuple")
if len(macro) == 1:
elif len(macro) == 2:
extensions[i] = ext
def get_source_files(self):
filenames = []
# Wouldn't it be neat if we knew the names of header files too...
for ext in self.extensions:
return filenames
def get_outputs(self):
# Sanity check the 'extensions' list -- can't assume this is being
# done in the same run as a 'build_extensions()' call (in fact, we
# can probably assume that it *isn't*!).
# And build the list of output (built) filenames. Note that this
# ignores the 'inplace' flag, and assumes everything goes in the
# "build" tree.
outputs = []
for ext in self.extensions:
return outputs
def build_extensions(self):
# First, sanity-check the 'extensions' list
if self.parallel:
def _build_extensions_parallel(self):
workers = self.parallel
if self.parallel is True:
workers = os.cpu_count() # may return None
from concurrent.futures import ThreadPoolExecutor
except ImportError:
workers = None
if workers is None:
with ThreadPoolExecutor(max_workers=workers) as executor:
futures = [executor.submit(self.build_extension, ext)
for ext in self.extensions]
for ext, fut in zip(self.extensions, futures):
with self._filter_build_errors(ext):
def _build_extensions_serial(self):
for ext in self.extensions:
with self._filter_build_errors(ext):
def _filter_build_errors(self, ext):
except (CCompilerError, DistutilsError, CompileError) as e:
if not ext.optional:
self.warn('building extension "%s" failed: %s' %
(, e))
def build_extension(self, ext):
sources = ext.sources
if sources is None or not isinstance(sources, (list, tuple)):
raise DistutilsSetupError(
"in 'ext_modules' option (extension '%s'), "
"'sources' must be present and must be "
"a list of source filenames" %
sources = list(sources)
ext_path = self.get_ext_fullpath(
depends = sources + ext.depends
if not (self.force or newer_group(depends, ext_path, 'newer')):
log.debug("skipping '%s' extension (up-to-date)",
else:"building '%s' extension",
# First, scan the sources for SWIG definition files (.i), run
# SWIG on 'em to create .c files, and modify the sources list
# accordingly.
sources = self.swig_sources(sources, ext)
# Next, compile the source code to object files.
# XXX not honouring 'define_macros' or 'undef_macros' -- the
# CCompiler API needs to change to accommodate this, and I
# want to do one thing at a time!
# Two possible sources for extra compiler arguments:
# - 'extra_compile_args' in Extension object
# - CFLAGS environment variable (not particularly
# elegant, but people seem to expect it and I
# guess it's useful)
# The environment variable should take precedence, and
# any sensible compiler will give precedence to later
# command line args. Hence we combine them in order:
extra_args = ext.extra_compile_args or []
macros = ext.define_macros[:]
for undef in ext.undef_macros:
objects = self.compiler.compile(sources,
# XXX outdated variable, kept here in case third-part code
# needs it.
self._built_objects = objects[:]
# Now link the object files together into a "shared object" --
# of course, first we have to figure out all the other things
# that go into the mix.
if ext.extra_objects:
extra_args = ext.extra_link_args or []
# Detect target language, if not provided
language = ext.language or self.compiler.detect_language(sources)
objects, ext_path,
def swig_sources(self, sources, extension):
"""Walk the list of source files in 'sources', looking for SWIG
interface (.i) files. Run SWIG on all that are found, and
return a modified 'sources' list with SWIG source files replaced
by the generated C (or C++) files.
new_sources = []
swig_sources = []
swig_targets = {}
# XXX this drops generated C/C++ files into the source tree, which
# is fine for developers who want to distribute the generated
# source -- but there should be an option to put SWIG output in
# the temp dir.
if self.swig_cpp:
log.warn("--swig-cpp is deprecated - use --swig-opts=-c++")
if self.swig_cpp or ('-c++' in self.swig_opts) or \
('-c++' in extension.swig_opts):
target_ext = '.cpp'
target_ext = '.c'
for source in sources:
(base, ext) = os.path.splitext(source)
if ext == ".i": # SWIG interface file
new_sources.append(base + '_wrap' + target_ext)
swig_targets[source] = new_sources[-1]
if not swig_sources:
return new_sources
swig = self.swig or self.find_swig()
swig_cmd = [swig, "-python"]
if self.swig_cpp:
# Do not override commandline arguments
if not self.swig_opts:
for o in extension.swig_opts:
for source in swig_sources:
target = swig_targets[source]"swigging %s to %s", source, target)
self.spawn(swig_cmd + ["-o", target, source])
return new_sources
def find_swig(self):
"""Return the name of the SWIG executable. On Unix, this is
just "swig" -- it should be in the PATH. Tries a bit harder on
if == "posix":
return "swig"
elif == "nt":
# Look for SWIG in its standard installation directory on
# Windows (or so I presume!). If we find it there, great;
# if not, act like Unix and assume it's in the PATH.
for vers in ("1.3", "1.2", "1.1"):
fn = os.path.join("c:\\swig%s" % vers, "swig.exe")
if os.path.isfile(fn):
return fn
return "swig.exe"
raise DistutilsPlatformError(
"I don't know how to find (much less run) SWIG "
"on platform '%s'" %
# -- Name generators -----------------------------------------------
# (extension names, filenames, whatever)
def get_ext_fullpath(self, ext_name):
"""Returns the path of the filename for a given extension.
The file is located in `build_lib` or directly in the package
(inplace option).
fullname = self.get_ext_fullname(ext_name)
modpath = fullname.split('.')
filename = self.get_ext_filename(modpath[-1])
if not self.inplace:
# no further work needed
# returning :
# build_dir/package/path/filename
filename = os.path.join(*modpath[:-1]+[filename])
return os.path.join(self.build_lib, filename)
# the inplace option requires to find the package directory
# using the build_py command for that
package = '.'.join(modpath[0:-1])
build_py = self.get_finalized_command('build_py')
package_dir = os.path.abspath(build_py.get_package_dir(package))
# returning
# package_dir/filename
return os.path.join(package_dir, filename)
def get_ext_fullname(self, ext_name):
"""Returns the fullname of a given extension name.
Adds the `package.` prefix"""
if self.package is None:
return ext_name
return self.package + '.' + ext_name
def get_ext_filename(self, ext_name):
r"""Convert the name of an extension (eg. "") into the name
of the file from which it will be loaded (eg. "foo/", or
from distutils.sysconfig import get_config_var
ext_path = ext_name.split('.')
ext_suffix = get_config_var('EXT_SUFFIX')
return os.path.join(*ext_path) + ext_suffix
def get_export_symbols(self, ext):
"""Return the list of symbols that a shared extension has to
export. This either uses 'ext.export_symbols' or, if it's not
provided, "PyInit_" + module_name. Only relevant on Windows, where
the .pyd file (DLL) must export the module "PyInit_" function.
initfunc_name = "PyInit_" +'.')[-1]
if initfunc_name not in ext.export_symbols:
return ext.export_symbols
def get_libraries(self, ext):
"""Return the list of libraries to link against when building a
shared extension. On most platforms, this is just 'ext.libraries';
on Windows, we add the Python library (eg. python20.dll).
# The python library is always needed on Windows. For MSVC, this
# is redundant, since the library is mentioned in a pragma in
# pyconfig.h that MSVC groks. The other Windows compilers all seem
# to need it mentioned explicitly, though, so that's what we do.
# Append '_d' to the python import library on debug builds.
if sys.platform == "win32":
from distutils._msvccompiler import MSVCCompiler
if not isinstance(self.compiler, MSVCCompiler):
template = "python%d%d"
if self.debug:
template = template + '_d'
pythonlib = (template %
(sys.hexversion >> 24, (sys.hexversion >> 16) & 0xff))
# don't extend ext.libraries, it may be shared with other
# extensions, it is a reference to the original list
return ext.libraries + [pythonlib]
return ext.libraries
elif sys.platform == 'darwin':
# Don't use the default code below
return ext.libraries
elif sys.platform[:3] == 'aix':
# Don't use the default code below
return ext.libraries
from distutils import sysconfig
if sysconfig.get_config_var('Py_ENABLE_SHARED'):
pythonlib = 'python{}.{}{}'.format(
sys.hexversion >> 24, (sys.hexversion >> 16) & 0xff,
return ext.libraries + [pythonlib]
return ext.libraries
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