3.1.1. Requirements for optional modules

Some optional modules of the standard library require third-party libraries installed for development (for example, header files must be available).

Missing requirements are reported in the configure output. Modules that are missing due to missing dependencies are listed near the end of the make output, sometimes using an internal name, for example, _ctypes for ctypes module.

If you distribute a CPython interpreter without optional modules, it’s best practice to advise users, who generally expect that standard library modules are available.

Dependencies to build optional modules are:

Note that the table does not include all optional modules; in particular, platform-specific modules like winreg are not listed here.

3.2.1. configure script

The make regen-configure command regenerates the aclocal.m4 file and the configure script using the Tools/build/regen-configure.sh shell script which uses an Ubuntu container to get the same tools versions and have a reproducible output.

The container is optional, the following command can be run locally:

autoreconf -ivf -Werror

The generated files can change depending on the exact versions of the tools used. The container that CPython uses has Autoconf 2.72, aclocal from Automake 1.16.5, and pkg-config 1.8.1.

3.3.1. General Options

--enable-loadable-sqlite-extensions

Support loadable extensions in the _sqlite extension module (default is no) of the sqlite3 module.

See the sqlite3.Connection.enable_load_extension() method of the sqlite3 module.

Added in version 3.6.

--disable-ipv6

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

--enable-big-digits=[15|30]

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

By default, the digit size is 30.

Define the PYLONG_BITS_IN_DIGIT to 15 or 30.

See sys.int_info.bits_per_digit.

--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).

Changed in version 3.11: The default suffix on WASM platform is one of .js, .html or .wasm.

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

Select the default time zone search path for zoneinfo.TZPATH. See the Compile-time configuration of the zoneinfo module.

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

See os.pathsep path separator.

Added in version 3.9.

--without-decimal-contextvar

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

See decimal.HAVE_CONTEXTVAR and the contextvars module.

Added in version 3.9.

--with-dbmliborder=<list of backend names>

Override order to check db backends for the dbm module

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

• ndbm;
• gdbm;
• bdb.

--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 PYTHONCOERCECLOCALE and the PEP 538.

--with-platlibdir=DIRNAME

Python library directory name (default is lib).

Fedora and SuSE use lib64 on 64-bit platforms.

See sys.platlibdir.

Added in version 3.9.

--with-wheel-pkg-dir=PATH

Directory of wheel packages used by the 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 ensurepip._bundled package.

Added in version 3.10.

--with-pkg-config=[check|yes|no]

Whether configure should use pkg-config to detect build dependencies.

• check (default): pkg-config is optional
• yes: pkg-config is mandatory
• no: configure does not use pkg-config even when present

Added in version 3.11.

--enable-pystats

Turn on internal Python performance statistics gathering.

By default, statistics gathering is off. Use python3 -X pystats command or set PYTHONSTATS=1 environment variable to turn on statistics gathering at Python startup.

At Python exit, dump statistics if statistics gathering was on and not cleared.

Effects:

• Add -X pystats command line option.
• Add PYTHONSTATS environment variable.
• Define the Py_STATS macro.

• Add functions to the sys module:

  • sys._stats_on(): Turns on statistics gathering.
  • sys._stats_off(): Turns off statistics gathering.
  • sys._stats_clear(): Clears the statistics.
  • sys._stats_dump(): Dump statistics to file, and clears the statistics.

The statistics will be dumped to a arbitrary (probably unique) file in /tmp/py_stats/ (Unix) or C:\temp\py_stats\ (Windows). If that directory does not exist, results will be printed on stderr.

Use Tools/scripts/summarize_stats.py to read the stats.

Statistics:

• Opcode:

  • Specialization: success, failure, hit, deferred, miss, deopt, failures;
  • Execution count;
  • Pair count.

• Call:

  • Inlined Python calls;
  • PyEval calls;
  • Frames pushed;
  • Frame object created;
  • Eval calls: vector, generator, legacy, function VECTORCALL, build class, slot, function “ex”, API, method.

• Object:

  • incref and decref;
  • interpreter incref and decref;
  • allocations: all, 512 bytes, 4 kiB, big;
  • free;
  • to/from free lists;
  • dictionary materialized/dematerialized;
  • type cache;
  • optimization attempts;
  • optimization traces created/executed;
  • uops executed.

• Garbage collector:

  • Garbage collections;
  • Objects visited;
  • Objects collected.

Added in version 3.11.

--disable-gil

Enables support for running Python without the global interpreter lock (GIL): free-threaded build.

Defines the Py_GIL_DISABLED macro and adds "t" to sys.abiflags.

See Free-threaded CPython for more detail.

Added in version 3.13.

--enable-experimental-jit=[no|yes|yes-off|interpreter]

Indicate how to integrate the experimental just-in-time compiler.

• no: Don’t build the JIT.
• yes: Enable the JIT. To disable it at runtime, set the environment variable PYTHON_JIT=0.
• yes-off: Build the JIT, but disable it by default. To enable it at runtime, set the environment variable PYTHON_JIT=1.
• interpreter: Enable the “JIT interpreter” (only useful for those debugging the JIT itself). To disable it at runtime, set the environment variable PYTHON_JIT=0.

--enable-experimental-jit=no is the default behavior if the option is not provided, and --enable-experimental-jit is shorthand for --enable-experimental-jit=yes. See Tools/jit/README.md for more information, including how to install the necessary build-time dependencies.

Note

When building CPython with JIT enabled, ensure that your system has Python 3.11 or later installed.

Added in version 3.13.

PKG_CONFIG

Path to pkg-config utility.

PKG_CONFIG_LIBDIR

PKG_CONFIG_PATH

pkg-config options.

3.3.2. C compiler options

CC

C compiler command.

CFLAGS

C compiler flags.

CPP

C preprocessor command.

CPPFLAGS

C preprocessor flags, e.g. -Iinclude_dir.

3.3.3. Linker options

LDFLAGS

Linker flags, e.g. -Llibrary_directory.

LIBS

Libraries to pass to the linker, e.g. -llibrary.

MACHDEP

Name for machine-dependent library files.

3.3.4. Options for third-party dependencies

BZIP2_CFLAGS

BZIP2_LIBS

C compiler and linker flags to link Python to libbz2, used by bz2 module, overriding pkg-config.

CURSES_CFLAGS

CURSES_LIBS

C compiler and linker flags for libncurses or libncursesw, used by curses module, overriding pkg-config.

GDBM_CFLAGS

GDBM_LIBS

C compiler and linker flags for gdbm.

LIBEDIT_CFLAGS

LIBEDIT_LIBS

C compiler and linker flags for libedit, used by readline module, overriding pkg-config.

LIBFFI_CFLAGS

LIBFFI_LIBS

C compiler and linker flags for libffi, used by ctypes module, overriding pkg-config.

LIBMPDEC_CFLAGS

LIBMPDEC_LIBS

C compiler and linker flags for libmpdec, used by decimal module, overriding pkg-config.

Note

These environment variables have no effect unless --with-system-libmpdec is specified.

LIBLZMA_CFLAGS

LIBLZMA_LIBS

C compiler and linker flags for liblzma, used by lzma module, overriding pkg-config.

LIBREADLINE_CFLAGS

LIBREADLINE_LIBS

C compiler and linker flags for libreadline, used by readline module, overriding pkg-config.

LIBSQLITE3_CFLAGS

LIBSQLITE3_LIBS

C compiler and linker flags for libsqlite3, used by sqlite3 module, overriding pkg-config.

LIBUUID_CFLAGS

LIBUUID_LIBS

C compiler and linker flags for libuuid, used by uuid module, overriding pkg-config.

LIBZSTD_CFLAGS

LIBZSTD_LIBS

C compiler and linker flags for libzstd, used by compression.zstd module, overriding pkg-config.

Added in version 3.14.

PANEL_CFLAGS

PANEL_LIBS

C compiler and linker flags for PANEL, overriding pkg-config.

C compiler and linker flags for libpanel or libpanelw, used by curses.panel module, overriding pkg-config.

TCLTK_CFLAGS

TCLTK_LIBS

C compiler and linker flags for TCLTK, overriding pkg-config.

ZLIB_CFLAGS

ZLIB_LIBS

C compiler and linker flags for libzlib, used by gzip module, overriding pkg-config.

3.3.5. WebAssembly Options

--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.

Added in version 3.11.

--enable-wasm-pthreads

Turn on pthreads support for WASM.

Added in version 3.11.

3.3.6. Install Options

--prefix=PREFIX

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

This value can be retrieved at runtime using sys.prefix.

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

--exec-prefix=EPREFIX

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

This value can be retrieved at runtime using sys.exec_prefix.

--disable-test-modules

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

Added in version 3.10.

--with-ensurepip=[upgrade|install|no]

Select the 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;

Added in version 3.6.

3.3.7. 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.

--enable-optimizations

Enable Profile Guided Optimization (PGO) using 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.

Note

During the build, you may encounter compiler warnings about profile data not being available for some source files. These warnings are harmless, as only a subset of the code is exercised during profile data acquisition. To disable these warnings on Clang, manually suppress them by adding -Wno-profile-instr-unprofiled to CFLAGS.

Added in version 3.6.

Changed in version 3.10: Use -fno-semantic-interposition on GCC.

PROFILE_TASK

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

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

Added in version 3.8.

Changed in version 3.13: Task failure is no longer ignored silently.

--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).

Added in version 3.6.

Added in version 3.11: To use ThinLTO feature, use --with-lto=thin on Clang.

Changed in version 3.12: Use ThinLTO as the default optimization policy on Clang if the compiler accepts the flag.

--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 BOLT_INSTRUMENT_FLAGS and BOLT_APPLY_FLAGS configure variables can be defined to override the default set of arguments for llvm-bolt to instrument and apply BOLT data to binaries, respectively.

Added in version 3.12.

BOLT_APPLY_FLAGS

Arguments to llvm-bolt when creating a BOLT optimized binary.

Added in version 3.12.

BOLT_INSTRUMENT_FLAGS

Arguments to llvm-bolt when instrumenting binaries.

Added in version 3.12.

--with-computed-gotos

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

--with-tail-call-interp

Enable interpreters using tail calls in CPython. If enabled, enabling PGO (--enable-optimizations) is highly recommended. This option specifically requires a C compiler with proper tail call support, and the preserve_none calling convention. For example, Clang 19 and newer supports this feature.

Added in version 3.14.

--without-mimalloc

Disable the fast mimalloc allocator (enabled by default).

See also PYTHONMALLOC environment variable.

--without-pymalloc

Disable the specialized Python memory allocator pymalloc (enabled by default).

See also PYTHONMALLOC environment variable.

--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.

--enable-profiling

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

--with-strict-overflow

Add -fstrict-overflow to the C compiler flags (by default we add -fno-strict-overflow instead).

--without-remote-debug

Deactivate remote debugging support described in PEP 768 (enabled by default). When this flag is provided the code that allows the interpreter to schedule the execution of a Python file in a separate process as described in PEP 768 is not compiled. This includes both the functionality to schedule code to be executed and the functionality to receive code to be executed.

Py_REMOTE_DEBUG

This macro is defined by default, unless Python is configured with --without-remote-debug.

Note that even if the macro is defined, remote debugging may not be available (for example, on an incompatible platform).

Added in version 3.14.

3.3.8. Python Debug Build

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

Effects of a debug build:

• Display all warnings by default: the list of default warning filters is empty in the warnings module.
• Add d to sys.abiflags.
• Add sys.gettotalrefcount() function.
• Add -X showrefcount command line option.
• Add -d command line option and 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 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 --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 (gc.collect() function) runs some basic checks on objects consistency.
  • The Py_SAFE_DOWNCAST() macro checks for integer underflow and overflow when downcasting from wide types to narrow types.

See also the Python Development Mode and the --with-trace-refs configure option.

3.3.9. Debug options

--with-pydebug

Build Python in debug mode: define the Py_DEBUG macro (disabled by default).

--with-trace-refs

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

Effects:

• Define the Py_TRACE_REFS macro.
• Add sys.getobjects() function.
• Add PYTHONDUMPREFS environment variable.

The PYTHONDUMPREFS environment variable can be used to dump objects and reference counts still alive at Python exit.

Statically allocated objects are not traced.

Added in version 3.8.

Changed in version 3.13: This build is now ABI compatible with release build and debug build.

--with-assertions

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

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

See also the --with-pydebug option (debug build) which also enables assertions.

Added in version 3.6.

--with-valgrind

Enable Valgrind support (default is no).

--with-dtrace

Enable DTrace support (default is no).

See Instrumenting CPython with DTrace and SystemTap.

Added in version 3.6.

--with-address-sanitizer

Enable AddressSanitizer memory error detector, asan (default is no). To improve ASan detection capabilities you may also want to combine this with --without-pymalloc to disable the specialized small-object allocator whose allocations are not tracked by ASan.

Added in version 3.6.

--with-memory-sanitizer

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

Added in version 3.6.

--with-undefined-behavior-sanitizer

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

Added in version 3.6.

--with-thread-sanitizer

Enable ThreadSanitizer data race detector, tsan (default is no).

Added in version 3.13.

3.3.10. Linker options

--enable-shared

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

--without-static-libpython

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

Added in version 3.10.

3.3.11. Libraries options

--with-libs='lib1 ...'

Link against additional libraries (default is no).

--with-system-expat

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

--with-system-libmpdec

Build the _decimal extension module using an installed mpdecimal library, see the decimal module (default is yes).

Added in version 3.3.

Changed in version 3.13: Default to using the installed mpdecimal library.

Changed in version 3.15: A bundled copy of the library will no longer be selected implicitly if an installed mpdecimal library is not found. In Python 3.15 only, it can still be selected explicitly using --with-system-libmpdec=no or --without-system-libmpdec.

Deprecated since version 3.13, will be removed in version 3.16: A copy of the mpdecimal library sources will no longer be distributed with Python 3.16.

See also

LIBMPDEC_CFLAGS and LIBMPDEC_LIBS.

--with-readline=readline|editline

Designate a backend library for the readline module.

• readline: Use readline as the backend.
• editline: Use editline as the backend.

Added in version 3.10.

--without-readline

Don’t build the readline module (built by default).

Don’t define the HAVE_LIBREADLINE macro.

Added in version 3.10.

--with-libm=STRING

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

--with-libc=STRING

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

--with-openssl=DIR

Root of the OpenSSL directory.

Added in version 3.7.

--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 --with-openssl and pkg-config;
• DIR: set an explicit rpath.

Added in version 3.10.

3.3.12. Security Options

--with-hash-algorithm=[fnv|siphash13|siphash24]

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

• siphash13 (default);
• siphash24;
• fnv.

Added in version 3.4.

Added in version 3.11: siphash13 is added and it is the new default.

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

Built-in hash modules:

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

Added in version 3.9.

--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 ssl module.

Added in version 3.7.

Changed in version 3.10: The settings python and STRING also set TLS 1.2 as minimum protocol version.

--disable-safety

Disable compiler options that are recommended by OpenSSF for security reasons with no performance overhead. If this option is not enabled, CPython will be built based on safety compiler options with no slow down. When this option is enabled, CPython will not be built with the compiler options listed below.

The following compiler options are disabled with --disable-safety:

• -fstack-protector-strong: Enable run-time checks for stack-based buffer overflows.
• -Wtrampolines: Enable warnings about trampolines that require executable stacks.

Added in version 3.14.

--enable-slower-safety

Enable compiler options that are recommended by OpenSSF for security reasons which require overhead. If this option is not enabled, CPython will not be built based on safety compiler options which performance impact. When this option is enabled, CPython will be built with the compiler options listed below.

The following compiler options are enabled with --enable-slower-safety:

• -D_FORTIFY_SOURCE=3: Fortify sources with compile- and run-time checks for unsafe libc usage and buffer overflows.

Added in version 3.14.

3.3.13. macOS Options

See Mac/README.rst.

--enable-universalsdk

--enable-universalsdk=SDKDIR

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

--enable-framework

--enable-framework=INSTALLDIR

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

--with-universal-archs=ARCH

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

Options:

• universal2 (x86-64 and arm64);
• 32-bit (PPC and i386);
• 64-bit (PPC64 and x86-64);
• 3-way (i386, PPC and x86-64);
• intel (i386 and x86-64);
• intel-32 (i386);
• intel-64 (x86-64);
• all (PPC, i386, PPC64 and x86-64).

Note that values for this configuration item are not the same as the identifiers used for universal binary wheels on macOS. See the Python Packaging User Guide for details on the packaging platform compatibility tags used on macOS

--with-framework-name=FRAMEWORK

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

--with-app-store-compliance

--with-app-store-compliance=PATCH-FILE

The Python standard library contains strings that are known to trigger automated inspection tool errors when submitted for distribution by the macOS and iOS App Stores. If enabled, this option will apply the list of patches that are known to correct app store compliance. A custom patch file can also be specified. This option is disabled by default.

Added in version 3.13.

3.3.14. iOS Options

See iOS/README.rst.

--enable-framework=INSTALLDIR

Create a Python.framework. Unlike macOS, the INSTALLDIR argument specifying the installation path is mandatory.

--with-framework-name=FRAMEWORK

Specify the name for the framework (default: Python).

3.3.15. 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.

--build=BUILD

configure for building on BUILD, usually guessed by config.guess.

--host=HOST

cross-compile to build programs to run on HOST (target platform)

--with-build-python=path/to/python

path to build python binary for cross compiling

Added in version 3.11.

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

HOSTRUNNER

Program to run CPython for the host platform for cross-compilation.

Added in version 3.11.

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

3.4.1. Main files of the build system

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

3.4.2. 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 Modules/Setup).

3.4.3. Main Makefile targets

3.4.4. 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
<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 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
<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'

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 PyAPI_FUNC(), PyAPI_DATA() and PyMODINIT_FUNC macros of Include/exports.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 ImportError on import.

3.5.1. Preprocessor flags

CONFIGURE_CPPFLAGS

Value of CPPFLAGS variable passed to the ./configure script.

Added in version 3.6.

CPPFLAGS

(Objective) C/C++ preprocessor flags, e.g. -Iinclude_dir if you have headers in a nonstandard directory include_dir.

Both CPPFLAGS and LDFLAGS need to contain the shell’s value to be able to build extension modules using the directories specified in the environment variables.

BASECPPFLAGS

Added in version 3.4.

PY_CPPFLAGS

Extra preprocessor flags added for building the interpreter object files.

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

Added in version 3.2.

3.5.2. Compiler flags

CC

C compiler command.

Example: gcc -pthread.

CXX

C++ compiler command.

Example: g++ -pthread.

CFLAGS

C compiler flags.

CFLAGS_NODIST

CFLAGS_NODIST is used for building the interpreter and stdlib C extensions. Use it when a compiler flag should not be part of CFLAGS once Python is installed (gh-65320).

In particular, 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 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.

Added in version 3.5.

COMPILEALL_OPTS

Options passed to the compileall command line when building PYC files in make install. Default: -j0.

Added in version 3.12.

EXTRA_CFLAGS

Extra C compiler flags.

CONFIGURE_CFLAGS

Value of CFLAGS variable passed to the ./configure script.

Added in version 3.2.

CONFIGURE_CFLAGS_NODIST

Value of CFLAGS_NODIST variable passed to the ./configure script.

Added in version 3.5.

BASECFLAGS

Base compiler flags.

OPT

Optimization flags.

CFLAGS_ALIASING

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

Added in version 3.7.

CCSHARED

Compiler flags used to build a shared library.

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

CFLAGSFORSHARED

Extra C flags added for building the interpreter object files.

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

PY_CFLAGS

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

PY_CFLAGS_NODIST

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

Added in version 3.5.

PY_STDMODULE_CFLAGS

C flags used for building the interpreter object files.

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

Added in version 3.7.

PY_CORE_CFLAGS

Default: $(PY_STDMODULE_CFLAGS) -DPy_BUILD_CORE.

Added in version 3.2.

PY_BUILTIN_MODULE_CFLAGS

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

Default: $(PY_STDMODULE_CFLAGS) -DPy_BUILD_CORE_BUILTIN.

Added in version 3.8.

PURIFY

Purify command. Purify is a memory debugger program.

Default: empty string (not used).

3.5.3. Linker flags

LINKCC

Linker command used to build programs like python and _testembed.

Default: $(PURIFY) $(CC).

CONFIGURE_LDFLAGS

Value of LDFLAGS variable passed to the ./configure script.

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

Added in version 3.2.

LDFLAGS_NODIST

LDFLAGS_NODIST is used in the same manner as CFLAGS_NODIST. Use it when a linker flag should not be part of LDFLAGS once Python is installed (gh-65320).

In particular, 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 LDFLAGS would take precedence over user- and package-supplied -L flags.

CONFIGURE_LDFLAGS_NODIST

Value of LDFLAGS_NODIST variable passed to the ./configure script.

Added in version 3.8.

LDFLAGS

Linker flags, e.g. -Llib_dir if you have libraries in a nonstandard directory lib_dir.

Both CPPFLAGS and LDFLAGS need to contain the shell’s value to be able to build extension modules using the directories specified in the environment variables.

LIBS

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

Example: -lrt.

LDSHARED

Command to build a shared library.

Default: @LDSHARED@ $(PY_LDFLAGS).

BLDSHARED

Command to build libpython shared library.

Default: @BLDSHARED@ $(PY_CORE_LDFLAGS).

PY_LDFLAGS

Default: $(CONFIGURE_LDFLAGS) $(LDFLAGS).

PY_LDFLAGS_NODIST

Default: $(CONFIGURE_LDFLAGS_NODIST) $(LDFLAGS_NODIST).

Added in version 3.8.

PY_CORE_LDFLAGS

Linker flags used for building the interpreter object files.

Added in version 3.8.

Footnotes