List all ./configure script options using:

./configure --help

See also the :file:`Misc/SpecialBuilds.txt` in the Python source distribution.

.. cmdoption:: --enable-loadable-sqlite-extensions

   Support loadable extensions in the :mod:`_sqlite` extension module (default
   is no).

   See the :meth:`sqlite3.Connection.enable_load_extension` method of the
   :mod:`sqlite3` module.

   .. versionadded:: 3.6

.. cmdoption:: --disable-ipv6

   Disable IPv6 support (enabled by default if supported), see the
   :mod:`socket` module.

.. cmdoption:: --enable-big-digits=[15|30]

   Define the size in bits of Python :class:`int` digits: 15 or 30 bits.

   By default, the number of bits is selected depending on ``sizeof(void*)``:
   30 bits if ``void*`` size is 64-bit or larger, 15 bits otherwise.

   Define the ``PYLONG_BITS_IN_DIGIT`` to ``15`` or ``30``.

   See :data:`sys.int_info.bits_per_digit <sys.int_info>`.

.. cmdoption:: --with-cxx-main

.. cmdoption:: --with-cxx-main=COMPILER

   Compile the Python ``main()`` function and link Python executable with C++
   compiler: ``$CXX``, or *COMPILER* if specified.

.. cmdoption:: --with-suffix=SUFFIX

   Set the Python executable suffix to *SUFFIX*.

   The default suffix is ``.exe`` on Windows and macOS (``python.exe``
   executable), and an empty string on other platforms (``python`` executable).

.. cmdoption:: --with-tzpath=<list of absolute paths separated by pathsep>

   Select the default time zone search path for :data:`zoneinfo.TZPATH`.
   See the :ref:`Compile-time configuration
   <zoneinfo_data_compile_time_config>` of the :mod:`zoneinfo` module.

   Default: ``/usr/share/zoneinfo:/usr/lib/zoneinfo:/usr/share/lib/zoneinfo:/etc/zoneinfo``.

   See :data:`os.pathsep` path separator.

   .. versionadded:: 3.9

.. cmdoption:: --without-decimal-contextvar

   Build the ``_decimal`` extension module using a thread-local context rather
   than a coroutine-local context (default), see the :mod:`decimal` module.

   See :data:`decimal.HAVE_CONTEXTVAR` and the :mod:`contextvars` module.

   .. versionadded:: 3.9

.. cmdoption:: --with-dbmliborder=db1:db2:...

   Override order to check db backends for the :mod:`dbm` module

   A valid value is a colon (``:``) separated string with the backend names:

   * ``ndbm``;
   * ``gdbm``;
   * ``bdb``.

.. cmdoption:: --without-c-locale-coercion

   Disable C locale coercion to a UTF-8 based locale (enabled by default).

   Don't define the ``PY_COERCE_C_LOCALE`` macro.

   See :envvar:`PYTHONCOERCECLOCALE` and the :pep:`538`.

.. cmdoption:: --with-platlibdir=DIRNAME

   Python library directory name (default is ``lib``).

   Fedora and SuSE use ``lib64`` on 64-bit platforms.

   See :data:`sys.platlibdir`.

   .. versionadded:: 3.9

.. cmdoption:: --with-wheel-pkg-dir=PATH

   Directory of wheel packages used by the :mod:`ensurepip` module
   (none by default).

   Some Linux distribution packaging policies recommend against bundling
   dependencies. For example, Fedora installs wheel packages in the
   ``/usr/share/python-wheels/`` directory and don't install the
   :mod:`ensurepip._bundled` package.

   .. versionadded:: 3.10

.. cmdoption:: --prefix=PREFIX

   Install architecture-independent files in PREFIX. On Unix, it
   defaults to :file:`/usr/local`.

   This value can be retrived at runtime using :data:`sys.prefix`.

   As an example, one can use ``--prefix="$HOME/.local/"`` to install
   a Python in its home directory.

.. cmdoption:: --exec-prefix=EPREFIX

   Install architecture-dependent files in EPREFIX, defaults to :option:`--prefix`.

   This value can be retrived at runtime using :data:`sys.exec_prefix`.

.. cmdoption:: --disable-test-modules

   Don't build nor install test modules, like the :mod:`test` package or the
   :mod:`_testcapi` extension module (built and installed by default).

   .. versionadded:: 3.10

.. cmdoption:: --with-ensurepip=[upgrade|install|no]

   Select the :mod:`ensurepip` command run on Python installation:

   * ``upgrade`` (default): run ``python -m ensurepip --altinstall --upgrade``
     command.
   * ``install``: run ``python -m ensurepip --altinstall`` command;
   * ``no``: don't run ensurepip;

   .. versionadded:: 3.6

Configuring Python using --enable-optimizations --with-lto (PGO + LTO) is recommended for best performance.

.. cmdoption:: --enable-optimizations

   Enable Profile Guided Optimization (PGO) using :envvar:`PROFILE_TASK`
   (disabled by default).

   The C compiler Clang requires ``llvm-profdata`` program for PGO. On
   macOS, GCC also requires it: GCC is just an alias to Clang on macOS.

   Disable also semantic interposition in libpython if ``--enable-shared`` and
   GCC is used: add ``-fno-semantic-interposition`` to the compiler and linker
   flags.

   .. versionadded:: 3.6

   .. versionchanged:: 3.10
      Use ``-fno-semantic-interposition`` on GCC.

.. envvar:: PROFILE_TASK

   Environment variable used in the Makefile: Python command line arguments for
   the PGO generation task.

   Default: ``-m test --pgo --timeout=$(TESTTIMEOUT)``.

   .. versionadded:: 3.8

.. cmdoption:: --with-lto

   Enable Link Time Optimization (LTO) in any build (disabled by default).

   The C compiler Clang requires ``llvm-ar`` for LTO (``ar`` on macOS), as well
   as an LTO-aware linker (``ld.gold`` or ``lld``).

   .. versionadded:: 3.6

.. cmdoption:: --with-computed-gotos

   Enable computed gotos in evaluation loop (enabled by default on supported
   compilers).

.. cmdoption:: --without-pymalloc

   Disable the specialized Python memory allocator :ref:`pymalloc <pymalloc>`
   (enabled by default).

   See also :envvar:`PYTHONMALLOC` environment variable.

.. cmdoption:: --without-doc-strings

   Disable static documentation strings to reduce the memory footprint (enabled
   by default). Documentation strings defined in Python are not affected.

   Don't define the ``WITH_DOC_STRINGS`` macro.

   See the ``PyDoc_STRVAR()`` macro.

.. cmdoption:: --enable-profiling

   Enable C-level code profiling with ``gprof`` (disabled by default).

A debug build is Python built with the :option:`--with-pydebug` configure option.

Effects of a debug build:

• Display all warnings by default: the list of default warning filters is empty in the :mod:`warnings` module.
• Add d to :data:`sys.abiflags`.
• Add :func:`sys.gettotalrefcount` function.
• Add :option:`-X showrefcount <-X>` command line option.
• Add :envvar:`PYTHONTHREADDEBUG` environment variable.
• Add support for the __ltrace__ variable: enable low-level tracing in the bytecode evaluation loop if the variable is defined.
• Install :ref:`debug hooks on memory allocators <default-memory-allocators>` to detect buffer overflow and other memory errors.
• Define Py_DEBUG and Py_REF_DEBUG macros.
• Add runtime checks: code surroundeded by #ifdef Py_DEBUG and #endif. Enable assert(...) and _PyObject_ASSERT(...) assertions: don't set the NDEBUG macro (see also the :option:`--with-assertions` configure option). Main runtime checks:
  • Add sanity checks on the function arguments.
  • Unicode and int objects are created with their memory filled with a pattern to detect usage of uninitialized objects.
  • Ensure that functions which can clear or replace the current exception are not called with an exception raised.
  • The garbage collector (:func:`gc.collect` function) runs some basic checks on objects consistency.
  • The :c:macro:`Py_SAFE_DOWNCAST()` macro checks for integer underflow and overflow when downcasting from wide types to narrow types.

See also the :ref:`Python Development Mode <devmode>` and the :option:`--with-trace-refs` configure option.

.. versionchanged:: 3.8
   Release builds and debug builds are now ABI compatible: defining the
   ``Py_DEBUG`` macro no longer implies the ``Py_TRACE_REFS`` macro (see the
   :option:`--with-trace-refs` option), which introduces the only ABI
   incompatibility.

.. cmdoption:: --with-pydebug

   :ref:`Build Python in debug mode <debug-build>`: define the ``Py_DEBUG``
   macro (disabled by default).

.. cmdoption:: --with-trace-refs

   Enable tracing references for debugging purpose (disabled by default).

   Effects:

   * Define the ``Py_TRACE_REFS`` macro.
   * Add :func:`sys.getobjects` function.
   * Add :envvar:`PYTHONDUMPREFS` environment variable.

   This build is not ABI compatible with release build (default build) or debug
   build (``Py_DEBUG`` and ``Py_REF_DEBUG`` macros).

   .. versionadded:: 3.8

.. cmdoption:: --with-assertions

   Build with C assertions enabled (default is no): ``assert(...);`` and
   ``_PyObject_ASSERT(...);``.

   If set, the ``NDEBUG`` macro is not defined in the :envvar:`OPT` compiler
   variable.

   See also the :option:`--with-pydebug` option (:ref:`debug build
   <debug-build>`) which also enables assertions.

   .. versionadded:: 3.6

.. cmdoption:: --with-valgrind

   Enable Valgrind support (default is no).

.. cmdoption:: --with-dtrace

   Enable DTrace support (default is no).

   See :ref:`Instrumenting CPython with DTrace and SystemTap
   <instrumentation>`.

   .. versionadded:: 3.6

.. cmdoption:: --with-address-sanitizer

   Enable AddressSanitizer memory error detector, ``asan`` (default is no).

   .. versionadded:: 3.6

.. cmdoption:: --with-memory-sanitizer

   Enable MemorySanitizer allocation error detector, ``msan`` (default is no).

   .. versionadded:: 3.6

.. cmdoption:: --with-undefined-behavior-sanitizer

   Enable UndefinedBehaviorSanitizer undefined behaviour detector, ``ubsan``
   (default is no).

   .. versionadded:: 3.6

.. cmdoption:: --enable-shared

   Enable building a shared Python library: ``libpython`` (default is no).

.. cmdoption:: --without-static-libpython

   Do not build ``libpythonMAJOR.MINOR.a`` and do not install ``python.o``
   (built and enabled by default).

   .. versionadded:: 3.10

.. cmdoption:: --with-libs='lib1 ...'

   Link against additional libraries (default is no).

.. cmdoption:: --with-system-expat

   Build the :mod:`pyexpat` module using an installed ``expat`` library
   (default is no).

.. cmdoption:: --with-system-ffi

   Build the :mod:`_ctypes` extension module using an installed ``ffi``
   library, see the :mod:`ctypes` module (default is system-dependent).

.. cmdoption:: --with-system-libmpdec

   Build the ``_decimal`` extension module using an installed ``mpdec``
   library, see the :mod:`decimal` module (default is no).

   .. versionadded:: 3.3

.. cmdoption:: --with-readline=editline

   Use ``editline`` library for backend of the :mod:`readline` module.

   Define the ``WITH_EDITLINE`` macro.

   .. versionadded:: 3.10

.. cmdoption:: --without-readline

   Don't build the :mod:`readline` module (built by default).

   Don't define the ``HAVE_LIBREADLINE`` macro.

   .. versionadded:: 3.10

.. cmdoption:: --with-tcltk-includes='-I...'

   Override search for Tcl and Tk include files.

.. cmdoption:: --with-tcltk-libs='-L...'

   Override search for Tcl and Tk libraries.

.. cmdoption:: --with-libm=STRING

   Override ``libm`` math library to *STRING* (default is system-dependent).

.. cmdoption:: --with-libc=STRING

   Override ``libc`` C library to *STRING* (default is system-dependent).

.. cmdoption:: --with-openssl=DIR

   Root of the OpenSSL directory.

   .. versionadded:: 3.7

.. cmdoption:: --with-openssl-rpath=[no|auto|DIR]

   Set runtime library directory (rpath) for OpenSSL libraries:

   * ``no`` (default): don't set rpath;
   * ``auto``: auto-detect rpath from :option:`--with-openssl` and
     ``pkg-config``;
   * *DIR*: set an explicit rpath.

   .. versionadded:: 3.10

.. cmdoption:: --with-hash-algorithm=[fnv|siphash24]

   Select hash algorithm for use in ``Python/pyhash.c``:

   * ``siphash24`` (default).
   * ``fnv``;

   .. versionadded:: 3.4

.. cmdoption:: --with-builtin-hashlib-hashes=md5,sha1,sha256,sha512,sha3,blake2

   Built-in hash modules:

   * ``md5``;
   * ``sha1``;
   * ``sha256``;
   * ``sha512``;
   * ``sha3`` (with shake);
   * ``blake2``.

   .. versionadded:: 3.9

.. cmdoption:: --with-ssl-default-suites=[python|openssl|STRING]

   Override the OpenSSL default cipher suites string:

   * ``python`` (default): use Python's preferred selection;
   * ``openssl``: leave OpenSSL's defaults untouched;
   * *STRING*: use a custom string

   See the :mod:`ssl` module.

   .. versionadded:: 3.7

   .. versionchanged:: 3.10

      The settings ``python`` and *STRING* also set TLS 1.2 as minimum
      protocol version.

See Mac/README.rst.

.. cmdoption:: --enable-universalsdk

.. cmdoption:: --enable-universalsdk=SDKDIR

   Create a universal binary build. *SDKDIR* specifies which macOS SDK should
   be used to perform the build (default is no).

.. cmdoption:: --enable-framework

.. cmdoption:: --enable-framework=INSTALLDIR

   Create a Python.framework rather than a traditional Unix install. Optional
   *INSTALLDIR* specifies the installation path (default is no).

.. cmdoption:: --with-universal-archs=ARCH

   Specify the kind of universal binary that should be created. This option is
   only valid when :option:`--enable-universalsdk` is set.

   Options:

   * ``universal2``;
   * ``32-bit``;
   * ``64-bit``;
   * ``3-way``;
   * ``intel``;
   * ``intel-32``;
   * ``intel-64``;
   * ``all``.

.. cmdoption:: --with-framework-name=FRAMEWORK

   Specify the name for the python framework on macOS only valid when
   :option:`--enable-framework` is set (default: ``Python``).

• :file:`configure.ac` => :file:`configure`;
• :file:`Makefile.pre.in` => :file:`Makefile` (created by :file:`configure`);
• :file:`pyconfig.h` (created by :file:`configure`);
• :file:`Modules/Setup`: C extensions built by the Makefile using :file:`Module/makesetup` shell script;
• :file:`setup.py`: C extensions built using the :mod:`distutils` module.

• C files (.c) are built as object files (.o).
• A static libpython library (.a) is created from objects files.
• python.o and the static libpython library are linked into the final python program.
• C extensions are built by the Makefile (see :file:`Modules/Setup`) and python setup.py build.

• make: Build Python with the standard library.
• make platform:: build the python program, but don't build the standard library extension modules.
• make profile-opt: build Python using Profile Guided Optimization (PGO). You can use the configure :option:`--enable-optimizations` option to make this the default target of the make command (make all or just make).
• make buildbottest: Build Python and run the Python test suite, the same way than buildbots test Python. Set TESTTIMEOUT variable (in seconds) to change the test timeout (1200 by default: 20 minutes).
• make install: Build and install Python.
• make regen-all: Regenerate (almost) all generated files; make regen-stdlib-module-names and autoconf must be run separately for the remaining generated files.
• make clean: Remove built files.
• make distclean: Same than make clean, but remove also files created by the configure script.

Some C extensions are built as built-in modules, like the sys module. They are built with the Py_BUILD_CORE_BUILTIN macro defined. Built-in modules have no __file__ attribute:

>>> import sys
>>> sys
<module 'sys' (built-in)>
>>> sys.__file__
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: module 'sys' has no attribute '__file__'

Other C extensins are built as dynamic libraries, like the _asyncio module. They are built with the Py_BUILD_CORE_MODULE macro defined. Example on Linux x86-64:

>>> import _asyncio
>>> _asyncio
<module '_asyncio' from '/usr/lib64/python3.9/lib-dynload/_asyncio.cpython-39-x86_64-linux-gnu.so'>
>>> _asyncio.__file__
'/usr/lib64/python3.9/lib-dynload/_asyncio.cpython-39-x86_64-linux-gnu.so'

:file:`Modules/Setup` is used to generate Makefile targets to build C extensions. At the beginning of the files, C extensions are built as built-in modules. Extensions defined after the *shared* marker are built as dynamic libraries.

The :file:`setup.py` script only builds C extensions as shared libraries using the :mod:`distutils` module.

The :c:macro:`PyAPI_FUNC()`, :c:macro:`PyAPI_API()` and :c:macro:`PyMODINIT_FUNC()` macros of :file:`Include/pyport.h` are defined differently depending if the Py_BUILD_CORE_MODULE macro is defined:

• Use Py_EXPORTED_SYMBOL if the Py_BUILD_CORE_MODULE is defined
• Use Py_IMPORTED_SYMBOL otherwise.

If the Py_BUILD_CORE_BUILTIN macro is used by mistake on a C extension built as a shared library, its PyInit_xxx() function is not exported, causing an :exc:`ImportError` on import.

Options set by the ./configure script and environment variables and used by Makefile.

.. envvar:: CONFIGURE_CPPFLAGS

   Value of :envvar:`CPPFLAGS` variable passed to the ``./configure`` script.

   .. versionadded:: 3.6

.. envvar:: CPPFLAGS

   (Objective) C/C++ preprocessor flags, e.g. ``-I<include dir>`` if you have
   headers in a nonstandard directory ``<include dir>``.

   Both :envvar:`CPPFLAGS` and :envvar:`LDFLAGS` need to contain the shell's
   value for setup.py to be able to build extension modules using the
   directories specified in the environment variables.

.. envvar:: BASECPPFLAGS

   .. versionadded:: 3.4

.. envvar:: PY_CPPFLAGS

   Extra preprocessor flags added for building the interpreter object files.

   Default: ``$(BASECPPFLAGS) -I. -I$(srcdir)/Include $(CONFIGURE_CPPFLAGS) $(CPPFLAGS)``.

   .. versionadded:: 3.2

.. envvar:: CC

   C compiler command.

   Example: ``gcc -pthread``.

.. envvar:: MAINCC

   C compiler command used to build the ``main()`` function of programs like
   ``python``.

   Variable set by the :option:`--with-cxx-main` option of the configure
   script.

   Default: ``$(CC)``.

.. envvar:: CXX

   C++ compiler command.

   Used if the :option:`--with-cxx-main` option is used.

   Example: ``g++ -pthread``.

.. envvar:: CFLAGS

   C compiler flags.

.. envvar:: CFLAGS_NODIST

   :envvar:`CFLAGS_NODIST` is used for building the interpreter and stdlib C
   extensions.  Use it when a compiler flag should *not* be part of the
   distutils :envvar:`CFLAGS` once Python is installed (:issue:`21121`).

   In particular, :envvar:`CFLAGS` should not contain:

   * the compiler flag ``-I`` (for setting the search path for include files).
     The ``-I`` flags are processed from left to right, and any flags in
     :envvar:`CFLAGS` would take precedence over user- and package-supplied ``-I``
     flags.

   * hardening flags such as ``-Werror`` because distributions cannot control
     whether packages installed by users conform to such heightened
     standards.

   .. versionadded:: 3.5

.. envvar:: EXTRA_CFLAGS

   Extra C compiler flags.

.. envvar:: CONFIGURE_CFLAGS

   Value of :envvar:`CFLAGS` variable passed to the ``./configure``
   script.

   .. versionadded:: 3.2

.. envvar:: CONFIGURE_CFLAGS_NODIST

   Value of :envvar:`CFLAGS_NODIST` variable passed to the ``./configure``
   script.

   .. versionadded:: 3.5

.. envvar:: BASECFLAGS

   Base compiler flags.

.. envvar:: OPT

   Optimization flags.

.. envvar:: CFLAGS_ALIASING

   Strict or non-strict aliasing flags used to compile ``Python/dtoa.c``.

   .. versionadded:: 3.7

.. envvar:: CCSHARED

   Compiler flags used to build a shared library.

   For example, ``-fPIC`` is used on Linux and on BSD.

.. envvar:: CFLAGSFORSHARED

   Extra C flags added for building the interpreter object files.

   Default: ``$(CCSHARED)`` when :option:`--enable-shared` is used, or an empty
   string otherwise.

.. envvar:: PY_CFLAGS

   Default: ``$(BASECFLAGS) $(OPT) $(CONFIGURE_CFLAGS) $(CFLAGS) $(EXTRA_CFLAGS)``.

.. envvar:: PY_CFLAGS_NODIST

   Default: ``$(CONFIGURE_CFLAGS_NODIST) $(CFLAGS_NODIST) -I$(srcdir)/Include/internal``.

   .. versionadded:: 3.5

.. envvar:: PY_STDMODULE_CFLAGS

   C flags used for building the interpreter object files.

   Default: ``$(PY_CFLAGS) $(PY_CFLAGS_NODIST) $(PY_CPPFLAGS) $(CFLAGSFORSHARED)``.

   .. versionadded:: 3.7

.. envvar:: PY_CORE_CFLAGS

   Default: ``$(PY_STDMODULE_CFLAGS) -DPy_BUILD_CORE``.

   .. versionadded:: 3.2

.. envvar:: PY_BUILTIN_MODULE_CFLAGS

   Compiler flags to build a standard library extension module as a built-in
   module, like the :mod:`posix` module.

   Default: ``$(PY_STDMODULE_CFLAGS) -DPy_BUILD_CORE_BUILTIN``.

   .. versionadded:: 3.8

.. envvar:: PURIFY

   Purify command. Purify is a memory debugger program.

   Default: empty string (not used).

.. envvar:: LINKCC

   Linker command used to build programs like ``python`` and ``_testembed``.

   Default: ``$(PURIFY) $(MAINCC)``.

.. envvar:: CONFIGURE_LDFLAGS

   Value of :envvar:`LDFLAGS` variable passed to the ``./configure`` script.

   Avoid assigning :envvar:`CFLAGS`, :envvar:`LDFLAGS`, etc. so users can use
   them on the command line to append to these values without stomping the
   pre-set values.

   .. versionadded:: 3.2

.. envvar:: LDFLAGS_NODIST

   :envvar:`LDFLAGS_NODIST` is used in the same manner as
   :envvar:`CFLAGS_NODIST`.  Use it when a linker flag should *not* be part of
   the distutils :envvar:`LDFLAGS` once Python is installed (:issue:`35257`).

   In particular, :envvar:`LDFLAGS` should not contain:

   * the compiler flag ``-L`` (for setting the search path for libraries).
     The ``-L`` flags are processed from left to right, and any flags in
     :envvar:`LDFLAGS` would take precedence over user- and package-supplied ``-L``
     flags.

.. envvar:: CONFIGURE_LDFLAGS_NODIST

   Value of :envvar:`LDFLAGS_NODIST` variable passed to the ``./configure``
   script.

   .. versionadded:: 3.8

.. envvar:: LDFLAGS

   Linker flags, e.g. ``-L<lib dir>`` if you have libraries in a nonstandard
   directory ``<lib dir>``.

   Both :envvar:`CPPFLAGS` and :envvar:`LDFLAGS` need to contain the shell's
   value for setup.py to be able to build extension modules using the
   directories specified in the environment variables.

.. envvar:: LIBS

   Linker flags to pass libraries to the linker when linking the Python
   executable.

   Example: ``-lrt``.

.. envvar:: LDSHARED

   Command to build a shared library.

   Default: ``@LDSHARED@ $(PY_LDFLAGS)``.

.. envvar:: BLDSHARED

   Command to build ``libpython`` shared library.

   Default: ``@BLDSHARED@ $(PY_CORE_LDFLAGS)``.

.. envvar:: PY_LDFLAGS

   Default: ``$(CONFIGURE_LDFLAGS) $(LDFLAGS)``.

.. envvar:: PY_LDFLAGS_NODIST

   Default: ``$(CONFIGURE_LDFLAGS_NODIST) $(LDFLAGS_NODIST)``.

   .. versionadded:: 3.8

.. envvar:: PY_CORE_LDFLAGS

   Linker flags used for building the interpreter object files.

   .. versionadded:: 3.8