diff --git a/.bzrignore b/.bzrignore
index 2527052..abca6b1 100644
--- a/.bzrignore
+++ b/.bzrignore
@@ -11,6 +11,7 @@
 build
 Makefile.pre
 platform
+pybuilddir.txt
 pyconfig.h
 libpython*.a
 libpython*.so*
diff --git a/.hgignore b/.hgignore
index de9bd5d..c51c53c 100644
--- a/.hgignore
+++ b/.hgignore
@@ -35,6 +35,7 @@
 Parser/pgen.stamp$
 ^core
 ^python-gdb.py
+^pybuilddir.txt
 
 syntax: glob
 python.exe-gdb.py
diff --git a/Lib/distutils/sysconfig.py b/Lib/distutils/sysconfig.py
index 250ef38..0c726d9 100644
--- a/Lib/distutils/sysconfig.py
+++ b/Lib/distutils/sysconfig.py
@@ -387,66 +387,11 @@
 
 def _init_posix():
     """Initialize the module as appropriate for POSIX systems."""
-    g = {}
-    # load the installed Makefile:
-    try:
-        filename = get_makefile_filename()
-        parse_makefile(filename, g)
-    except IOError, msg:
-        my_msg = "invalid Python installation: unable to open %s" % filename
-        if hasattr(msg, "strerror"):
-            my_msg = my_msg + " (%s)" % msg.strerror
-
-        raise DistutilsPlatformError(my_msg)
-
-    # load the installed pyconfig.h:
-    try:
-        filename = get_config_h_filename()
-        parse_config_h(file(filename), g)
-    except IOError, msg:
-        my_msg = "invalid Python installation: unable to open %s" % filename
-        if hasattr(msg, "strerror"):
-            my_msg = my_msg + " (%s)" % msg.strerror
-
-        raise DistutilsPlatformError(my_msg)
-
-    # On AIX, there are wrong paths to the linker scripts in the Makefile
-    # -- these paths are relative to the Python source, but when installed
-    # the scripts are in another directory.
-    if python_build:
-        g['LDSHARED'] = g['BLDSHARED']
-
-    elif get_python_version() < '2.1':
-        # The following two branches are for 1.5.2 compatibility.
-        if sys.platform == 'aix4':          # what about AIX 3.x ?
-            # Linker script is in the config directory, not in Modules as the
-            # Makefile says.
-            python_lib = get_python_lib(standard_lib=1)
-            ld_so_aix = os.path.join(python_lib, 'config', 'ld_so_aix')
-            python_exp = os.path.join(python_lib, 'config', 'python.exp')
-
-            g['LDSHARED'] = "%s %s -bI:%s" % (ld_so_aix, g['CC'], python_exp)
-
-        elif sys.platform == 'beos':
-            # Linker script is in the config directory.  In the Makefile it is
-            # relative to the srcdir, which after installation no longer makes
-            # sense.
-            python_lib = get_python_lib(standard_lib=1)
-            linkerscript_path = string.split(g['LDSHARED'])[0]
-            linkerscript_name = os.path.basename(linkerscript_path)
-            linkerscript = os.path.join(python_lib, 'config',
-                                        linkerscript_name)
-
-            # XXX this isn't the right place to do this: adding the Python
-            # library to the link, if needed, should be in the "build_ext"
-            # command.  (It's also needed for non-MS compilers on Windows, and
-            # it's taken care of for them by the 'build_ext.get_libraries()'
-            # method.)
-            g['LDSHARED'] = ("%s -L%s/lib -lpython%s" %
-                             (linkerscript, PREFIX, get_python_version()))
-
+    # _sysconfigdata is generated at build time, see the sysconfig module
+    from _sysconfigdata import build_time_vars
     global _config_vars
-    _config_vars = g
+    _config_vars = {}
+    _config_vars.update(build_time_vars)
 
 
 def _init_nt():
diff --git a/Lib/pprint.py b/Lib/pprint.py
index 910283e..330099d 100644
--- a/Lib/pprint.py
+++ b/Lib/pprint.py
@@ -37,7 +37,10 @@
 import sys as _sys
 import warnings
 
-from cStringIO import StringIO as _StringIO
+try:
+    from cStringIO import StringIO as _StringIO
+except ImportError:
+    from StringIO import StringIO as _StringIO
 
 __all__ = ["pprint","pformat","isreadable","isrecursive","saferepr",
            "PrettyPrinter"]
diff --git a/Lib/site.py b/Lib/site.py
index 54e5154..f1b0ae8 100644
--- a/Lib/site.py
+++ b/Lib/site.py
@@ -114,18 +114,6 @@
     sys.path[:] = L
     return known_paths
 
-# XXX This should not be part of site.py, since it is needed even when
-# using the -S option for Python.  See http://www.python.org/sf/586680
-def addbuilddir():
-    """Append ./build/lib.<platform> in case we're running in the build dir
-    (especially for Guido :-)"""
-    from sysconfig import get_platform
-    s = "build/lib.%s-%.3s" % (get_platform(), sys.version)
-    if hasattr(sys, 'gettotalrefcount'):
-        s += '-pydebug'
-    s = os.path.join(os.path.dirname(sys.path.pop()), s)
-    sys.path.append(s)
-
 
 def _init_pathinfo():
     """Return a set containing all existing directory entries from sys.path"""
@@ -537,9 +525,6 @@
 
     abs__file__()
     known_paths = removeduppaths()
-    if (os.name == "posix" and sys.path and
-        os.path.basename(sys.path[-1]) == "Modules"):
-        addbuilddir()
     if ENABLE_USER_SITE is None:
         ENABLE_USER_SITE = check_enableusersite()
     known_paths = addusersitepackages(known_paths)
diff --git a/Lib/sysconfig.py b/Lib/sysconfig.py
index d74ca39..aa69351 100644
--- a/Lib/sysconfig.py
+++ b/Lib/sysconfig.py
@@ -278,9 +278,10 @@
         return os.path.join(_PROJECT_BASE, "Makefile")
     return os.path.join(get_path('platstdlib'), "config", "Makefile")
 
-
-def _init_posix(vars):
-    """Initialize the module as appropriate for POSIX systems."""
+def _generate_posix_vars():
+    """Generate the Python module containing build-time variables."""
+    import pprint
+    vars = {}
     # load the installed Makefile:
     makefile = _get_makefile_filename()
     try:
@@ -308,6 +309,49 @@
     if _PYTHON_BUILD:
         vars['LDSHARED'] = vars['BLDSHARED']
 
+    # There's a chicken-and-egg situation on OS X with regards to the
+    # _sysconfigdata module after the changes introduced by #15298:
+    # get_config_vars() is called by get_platform() as part of the
+    # `make pybuilddir.txt` target -- which is a precursor to the
+    # _sysconfigdata.py module being constructed.  Unfortunately,
+    # get_config_vars() eventually calls _init_posix(), which attempts
+    # to import _sysconfigdata, which we won't have built yet.  In order
+    # for _init_posix() to work, if we're on Darwin, just mock up the
+    # _sysconfigdata module manually and populate it with the build vars.
+    # This is more than sufficient for ensuring the subsequent call to
+    # get_platform() succeeds.
+    name = '_sysconfigdata'
+    if 'darwin' in sys.platform:
+        import imp
+        module = imp.new_module(name)
+        module.build_time_vars = vars
+        sys.modules[name] = module
+
+    pybuilddir = 'build/lib.%s-%s' % (get_platform(), sys.version[:3])
+    if hasattr(sys, "gettotalrefcount"):
+        pybuilddir += '-pydebug'
+    try:
+        os.makedirs(pybuilddir)
+    except OSError:
+        pass
+    destfile = os.path.join(pybuilddir, name + '.py')
+
+    with open(destfile, 'wb') as f:
+        f.write('# system configuration generated and used by'
+                ' the sysconfig module\n')
+        f.write('build_time_vars = ')
+        pprint.pprint(vars, stream=f)
+
+    # Create file used for sys.path fixup -- see Modules/getpath.c
+    with open('pybuilddir.txt', 'w') as f:
+        f.write(pybuilddir)
+
+def _init_posix(vars):
+    """Initialize the module as appropriate for POSIX systems."""
+    # _sysconfigdata is generated at build time, see _generate_posix_vars()
+    from _sysconfigdata import build_time_vars
+    vars.update(build_time_vars)
+
 def _init_non_posix(vars):
     """Initialize the module as appropriate for NT"""
     # set basic install directories
@@ -565,3 +609,28 @@
 
 def get_python_version():
     return _PY_VERSION_SHORT
+
+
+def _print_dict(title, data):
+    for index, (key, value) in enumerate(sorted(data.items())):
+        if index == 0:
+            print '%s: ' % (title)
+        print '\t%s = "%s"' % (key, value)
+
+
+def _main():
+    """Display all information sysconfig detains."""
+    if '--generate-posix-vars' in sys.argv:
+        _generate_posix_vars()
+        return
+    print 'Platform: "%s"' % get_platform()
+    print 'Python version: "%s"' % get_python_version()
+    print 'Current installation scheme: "%s"' % _get_default_scheme()
+    print
+    _print_dict('Paths', get_paths())
+    print
+    _print_dict('Variables', get_config_vars())
+
+
+if __name__ == '__main__':
+    _main()
diff --git a/Makefile.pre.in b/Makefile.pre.in
index 93fb0cf..9d55550 100644
--- a/Makefile.pre.in
+++ b/Makefile.pre.in
@@ -437,15 +437,20 @@
 			Modules/python.o \
 			$(BLDLIBRARY) $(LIBS) $(MODLIBS) $(SYSLIBS) $(LDLAST)
 
-platform: $(BUILDPYTHON)
+platform: $(BUILDPYTHON) pybuilddir.txt
 	$(RUNSHARED) $(PYTHON_FOR_BUILD) -c 'import sys ; from sysconfig import get_platform ; print get_platform()+"-"+sys.version[0:3]' >platform
 
+# Create build directory and generate the sysconfig build-time data there.
+# pybuilddir.txt contains the name of the build dir and is used for
+# sys.path fixup -- see Modules/getpath.c.
+pybuilddir.txt: $(BUILDPYTHON)
+		$(RUNSHARED) $(PYTHON_FOR_BUILD) -S -m sysconfig --generate-posix-vars
 
 # Build the shared modules
 # Under GNU make, MAKEFLAGS are sorted and normalized; the 's' for
 # -s, --silent or --quiet is always the first char.
 # Under BSD make, MAKEFLAGS might be " -s -v x=y".
-sharedmods: $(BUILDPYTHON)
+sharedmods: $(BUILDPYTHON) pybuilddir.txt
 	@case "$$MAKEFLAGS" in \
 	    *\ -s*|s*) quiet="-q";; \
 	    *) quiet="";; \
@@ -955,7 +960,7 @@
 		else	true; \
 		fi; \
 	done
-	@for i in $(srcdir)/Lib/*.py $(srcdir)/Lib/*.doc $(srcdir)/Lib/*.egg-info ; \
+	@for i in $(srcdir)/Lib/*.py `cat pybuilddir.txt`/_sysconfigdata.py $(srcdir)/Lib/*.doc $(srcdir)/Lib/*.egg-info ; \
 	do \
 		if test -x $$i; then \
 			$(INSTALL_SCRIPT) $$i $(DESTDIR)$(LIBDEST); \
@@ -1133,6 +1138,7 @@
 		--install-scripts=$(BINDIR) \
 		--install-platlib=$(DESTSHARED) \
 		--root=$(DESTDIR)/
+	-rm $(DESTDIR)$(DESTSHARED)/_sysconfigdata.py*
 
 # Here are a couple of targets for MacOSX again, to install a full
 # framework-based Python. frameworkinstall installs everything, the
@@ -1288,6 +1294,7 @@
 		Modules/Setup Modules/Setup.local Modules/Setup.config \
 		Modules/ld_so_aix Modules/python.exp Misc/python.pc
 	-rm -f python*-gdb.py
+	-rm -f pybuilddir.txt
 	find $(srcdir) '(' -name '*.fdc' -o -name '*~' \
 			   -o -name '[@,#]*' -o -name '*.old' \
 			   -o -name '*.orig' -o -name '*.rej' \
diff --git a/Misc/NEWS b/Misc/NEWS
index e2ed81c..57e0cc6 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -14,6 +14,10 @@
 Library
 -------
 
+- Issue #13150, #17512: sysconfig no longer parses the Makefile and config.h
+  files when imported, instead doing it at build time.  This makes importing
+  sysconfig faster and reduces Python startup time by 20%.
+
 - Issue #13163: Rename operands in smtplib.SMTP._get_socket to correct names;
   fixes otherwise misleading output in tracebacks and when when debug is on.
 
diff --git a/Modules/getpath.c b/Modules/getpath.c
index 9faafa3..de96d47 100644
--- a/Modules/getpath.c
+++ b/Modules/getpath.c
@@ -335,12 +335,27 @@
         return 1;
     }
 
-    /* Check to see if argv[0] is in the build directory */
+    /* Check to see if argv[0] is in the build directory. "pybuilddir.txt"
+       is written by setup.py and contains the relative path to the location
+       of shared library modules. */
     strcpy(exec_prefix, argv0_path);
-    joinpath(exec_prefix, "Modules/Setup");
+    joinpath(exec_prefix, "pybuilddir.txt");
     if (isfile(exec_prefix)) {
-        reduce(exec_prefix);
-        return -1;
+      FILE *f = fopen(exec_prefix, "r");
+      if (f == NULL)
+	errno = 0;
+      else {
+	char rel_builddir_path[MAXPATHLEN+1];
+	size_t n;
+	n = fread(rel_builddir_path, 1, MAXPATHLEN, f);
+	rel_builddir_path[n] = '\0';
+	fclose(f);
+	if (n >= 0) {
+	  strcpy(exec_prefix, argv0_path);
+	  joinpath(exec_prefix, rel_builddir_path);
+	  return -1;
+	}
+      }
     }
 
     /* Search from argv0_path, until root is found */