**************** Configure Python **************** Build Requirements ================== Features required to build CPython: * A `C11 `_ compiler. `Optional C11 features `_ are not required. * Support for `IEEE 754 `_ floating point numbers and `floating point Not-a-Number (NaN) `_. * Support for threads. * OpenSSL 1.1.1 or newer for the :mod:`ssl` and :mod:`hashlib` modules. * On Windows, Microsoft Visual Studio 2017 or later is required. .. versionchanged:: 3.11 C11 compiler, IEEE 754 and NaN support are now required. On Windows, Visual Studio 2017 or later is required. .. versionchanged:: 3.10 OpenSSL 1.1.1 is now required. .. versionchanged:: 3.7 Thread support and OpenSSL 1.0.2 are now required. .. versionchanged:: 3.6 Selected C99 features are now required, like ```` and ``static inline`` functions. .. versionchanged:: 3.5 On Windows, Visual Studio 2015 or later is required. See also :pep:`7` "Style Guide for C Code" and :pep:`11` "CPython platform support". .. _configure-options: Configure Options ================= List all ``./configure`` script options using:: ./configure --help See also the :file:`Misc/SpecialBuilds.txt` in the Python source distribution. General Options --------------- .. 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 digit size is 30. Define the ``PYLONG_BITS_IN_DIGIT`` to ``15`` or ``30``. See :data:`sys.int_info.bits_per_digit `. .. cmdoption:: --with-suffix=SUFFIX Set the Python executable suffix to *SUFFIX*. The default suffix is ``.exe`` on Windows and macOS (``python.exe`` executable), ``.js`` on Emscripten node, ``.html`` on Emscripten browser, ``.wasm`` on WASI, and an empty string on other platforms (``python`` executable). .. versionchanged:: 3.11 The default suffix on WASM platform is one of ``.js``, ``.html`` or ``.wasm``. .. cmdoption:: --with-tzpath= Select the default time zone search path for :const:`zoneinfo.TZPATH`. See the :ref:`Compile-time configuration ` 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 :const:`decimal.HAVE_CONTEXTVAR` and the :mod:`contextvars` module. .. versionadded:: 3.9 .. cmdoption:: --with-dbmliborder= 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:: --without-freelists Disable all freelists except the empty tuple singleton. .. versionadded:: 3.11 .. 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:: --with-pkg-config=[check|yes|no] Whether configure should use :program:`pkg-config` to detect build dependencies. * ``check`` (default): :program:`pkg-config` is optional * ``yes``: :program:`pkg-config` is mandatory * ``no``: configure does not use :program:`pkg-config` even when present .. versionadded:: 3.11 .. cmdoption:: --enable-pystats Turn on internal statistics gathering. The statistics will be dumped to a arbitrary (probably unique) file in ``/tmp/py_stats/``, or ``C:\temp\py_stats\`` on Windows. If that directory does not exist, results will be printed on stdout. Use ``Tools/scripts/summarize_stats.py`` to read the stats. .. versionadded:: 3.11 WebAssembly Options ------------------- .. cmdoption:: --with-emscripten-target=[browser|node] Set build flavor for ``wasm32-emscripten``. * ``browser`` (default): preload minimal stdlib, default MEMFS. * ``node``: NODERAWFS and pthread support. .. versionadded:: 3.11 .. cmdoption:: --enable-wasm-dynamic-linking Turn on dynamic linking support for WASM. Dynamic linking enables ``dlopen``. File size of the executable increases due to limited dead code elimination and additional features. .. versionadded:: 3.11 .. cmdoption:: --enable-wasm-pthreads Turn on pthreads support for WASM. .. versionadded:: 3.11 Install Options --------------- .. 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="$HOME/.local/"`` to install a Python in its home directory. .. cmdoption:: --exec-prefix=EPREFIX Install architecture-dependent files in EPREFIX, defaults to :option:`--prefix`. This value can be retrived at runtime using :data:`sys.exec_prefix`. .. cmdoption:: --disable-test-modules Don't build nor install test modules, like the :mod:`test` package or the :mod:`_testcapi` extension module (built and installed by default). .. versionadded:: 3.10 .. cmdoption:: --with-ensurepip=[upgrade|install|no] Select the :mod:`ensurepip` command run on Python installation: * ``upgrade`` (default): run ``python -m ensurepip --altinstall --upgrade`` command. * ``install``: run ``python -m ensurepip --altinstall`` command; * ``no``: don't run ensurepip; .. versionadded:: 3.6 Performance options ------------------- Configuring Python using ``--enable-optimizations --with-lto`` (PGO + LTO) is recommended for best performance. The experimental ``--enable-bolt`` flag can also be used to improve performance. .. cmdoption:: --enable-optimizations Enable Profile Guided Optimization (PGO) using :envvar:`PROFILE_TASK` (disabled by default). The C compiler Clang requires ``llvm-profdata`` program for PGO. On macOS, GCC also requires it: GCC is just an alias to Clang on macOS. Disable also semantic interposition in libpython if ``--enable-shared`` and GCC is used: add ``-fno-semantic-interposition`` to the compiler and linker flags. .. versionadded:: 3.6 .. versionchanged:: 3.10 Use ``-fno-semantic-interposition`` on GCC. .. envvar:: PROFILE_TASK Environment variable used in the Makefile: Python command line arguments for the PGO generation task. Default: ``-m test --pgo --timeout=$(TESTTIMEOUT)``. .. versionadded:: 3.8 .. cmdoption:: --with-lto=[full|thin|no|yes] 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 .. versionadded:: 3.11 To use ThinLTO feature, use ``--with-lto=thin`` on Clang. .. versionchanged:: 3.12 Use ThinLTO as the default optimization policy on Clang if the compiler accepts the flag. .. cmdoption:: --enable-bolt Enable usage of the `BOLT post-link binary optimizer `_ (disabled by default). BOLT is part of the LLVM project but is not always included in their binary distributions. This flag requires that ``llvm-bolt`` and ``merge-fdata`` are available. BOLT is still a fairly new project so this flag should be considered experimental for now. Because this tool operates on machine code its success is dependent on a combination of the build environment + the other optimization configure args + the CPU architecture, and not all combinations are supported. BOLT versions before LLVM 16 are known to crash BOLT under some scenarios. Use of LLVM 16 or newer for BOLT optimization is strongly encouraged. The :envvar:`!BOLT_INSTRUMENT_FLAGS` and :envvar:`!BOLT_APPLY_FLAGS` :program:`configure` variables can be defined to override the default set of arguments for :program:`llvm-bolt` to instrument and apply BOLT data to binaries, respectively. .. versionadded:: 3.12 .. 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 ` (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). .. cmdoption:: --with-strict-overflow Add ``-fstrict-overflow`` to the C compiler flags (by default we add ``-fno-strict-overflow`` instead). .. _debug-build: Python Debug Build ------------------ 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 :option:`-d` command line option and :envvar:`PYTHONDEBUG` environment variable to debug the parser. * Add support for the ``__lltrace__`` variable: enable low-level tracing in the bytecode evaluation loop if the variable is defined. * Install :ref:`debug hooks on memory allocators ` to detect buffer overflow and other memory errors. * Define ``Py_DEBUG`` and ``Py_REF_DEBUG`` macros. * Add runtime checks: code surrounded 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. * Check that deallocator functions don't change the current exception. * 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 ` 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. Debug options ------------- .. cmdoption:: --with-pydebug :ref:`Build Python in debug mode `: 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 `) 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 `. .. 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 Linker options -------------- .. 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 Libraries options ----------------- .. 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-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-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 Security Options ---------------- .. cmdoption:: --with-hash-algorithm=[fnv|siphash13|siphash24] Select hash algorithm for use in ``Python/pyhash.c``: * ``siphash13`` (default); * ``siphash24``; * ``fnv``. .. versionadded:: 3.4 .. versionadded:: 3.11 ``siphash13`` is added and it is the new default. .. 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. macOS Options ------------- 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``). Cross Compiling Options ----------------------- Cross compiling, also known as cross building, can be used to build Python for another CPU architecture or platform. Cross compiling requires a Python interpreter for the build platform. The version of the build Python must match the version of the cross compiled host Python. .. cmdoption:: --build=BUILD configure for building on BUILD, usually guessed by :program:`config.guess`. .. cmdoption:: --host=HOST cross-compile to build programs to run on HOST (target platform) .. cmdoption:: --with-build-python=path/to/python path to build ``python`` binary for cross compiling .. versionadded:: 3.11 .. cmdoption:: CONFIG_SITE=file An environment variable that points to a file with configure overrides. Example *config.site* file:: # config.site-aarch64 ac_cv_buggy_getaddrinfo=no ac_cv_file__dev_ptmx=yes ac_cv_file__dev_ptc=no Cross compiling example:: CONFIG_SITE=config.site-aarch64 ../configure \ --build=x86_64-pc-linux-gnu \ --host=aarch64-unknown-linux-gnu \ --with-build-python=../x86_64/python Python Build System =================== Main files of the build system ------------------------------ * :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 ``setuptools`` package. Main build steps ---------------- * 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``. Main Makefile targets --------------------- * ``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. C extensions ------------ 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 >>> sys.__file__ Traceback (most recent call last): File "", line 1, in AttributeError: module 'sys' has no attribute '__file__' Other C extensions 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 >>> _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. Compiler and linker flags ========================= Options set by the ``./configure`` script and environment variables and used by ``Makefile``. Preprocessor flags ------------------ .. 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`` if you have headers in a nonstandard directory ````. 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) $(CPPFLAGS)``. .. versionadded:: 3.2 Compiler flags -------------- .. envvar:: CC C compiler command. Example: ``gcc -pthread``. .. envvar:: CXX C++ compiler command. Example: ``g++ -pthread``. .. envvar:: CFLAGS C compiler flags. .. envvar:: CFLAGS_NODIST :envvar:`CFLAGS_NODIST` is used for building the interpreter and stdlib C extensions. Use it when a compiler flag should *not* be part of the distutils :envvar:`CFLAGS` once Python is installed (:issue:`21121`). In particular, :envvar:`CFLAGS` should not contain: * the compiler flag ``-I`` (for setting the search path for include files). The ``-I`` flags are processed from left to right, and any flags in :envvar:`CFLAGS` would take precedence over user- and package-supplied ``-I`` flags. * hardening flags such as ``-Werror`` because distributions cannot control whether packages installed by users conform to such heightened standards. .. versionadded:: 3.5 .. envvar:: COMPILEALL_OPTS Options passed to the :mod:`compileall` command line when building PYC files in ``make install``. Default: ``-j0``. .. versionadded:: 3.12 .. envvar:: EXTRA_CFLAGS Extra C compiler flags. .. envvar:: CONFIGURE_CFLAGS Value of :envvar:`CFLAGS` variable passed to the ``./configure`` script. .. versionadded:: 3.2 .. envvar:: CONFIGURE_CFLAGS_NODIST Value of :envvar:`CFLAGS_NODIST` variable passed to the ``./configure`` script. .. versionadded:: 3.5 .. envvar:: BASECFLAGS Base compiler flags. .. envvar:: OPT Optimization flags. .. envvar:: CFLAGS_ALIASING Strict or non-strict aliasing flags used to compile ``Python/dtoa.c``. .. versionadded:: 3.7 .. envvar:: CCSHARED Compiler flags used to build a shared library. For example, ``-fPIC`` is used on Linux and on BSD. .. envvar:: CFLAGSFORSHARED Extra C flags added for building the interpreter object files. Default: ``$(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: ``$(PY_STDMODULE_CFLAGS) -DPy_BUILD_CORE_BUILTIN``. .. versionadded:: 3.8 .. envvar:: PURIFY Purify command. Purify is a memory debugger program. Default: empty string (not used). Linker flags ------------ .. envvar:: LINKCC Linker command used to build programs like ``python`` and ``_testembed``. Default: ``$(PURIFY) $(CC)``. .. 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`` if you have libraries in a nonstandard directory ````. 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