3.2.1.configure script¶

Themakeregen-configure command regenerates theaclocal.m4 file andtheconfigure script using theTools/build/regen-configure.sh shellscript which uses an Ubuntu container to get the same tools versions and have areproducible output.

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

autoreconf-ivf-Werror

The generated files can change depending on the exactautoconf-archive,aclocal andpkg-config versions.

3.3.1.General Options¶

--enable-loadable-sqlite-extensions¶

Support loadable extensions in the_sqlite extension module (defaultis no) of thesqlite3 module.

See thesqlite3.Connection.enable_load_extension() method of thesqlite3 module.

Added in version 3.6.

--disable-ipv6¶

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

--enable-big-digits=[15|30]¶

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

By default, the digit size is 30.

Define thePYLONG_BITS_IN_DIGIT to15 or30.

Seesys.int_info.bits_per_digit.

--with-suffix=SUFFIX¶

Set the Python executable suffix toSUFFIX.

The default suffix is.exe on Windows and macOS (python.exeexecutable),.js on Emscripten node,.html on Emscripten browser,.wasm on WASI, and an empty string on other platforms (pythonexecutable).

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

--with-tzpath=<listofabsolutepathsseparatedbypathsep>¶

Select the default time zone search path forzoneinfo.TZPATH.See theCompile-time configuration of thezoneinfo module.

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

Seeos.pathsep path separator.

Added in version 3.9.

--without-decimal-contextvar¶

Build the_decimal extension module using a thread-local context ratherthan a coroutine-local context (default), see thedecimal module.

Seedecimal.HAVE_CONTEXTVAR and thecontextvars module.

Added in version 3.9.

--with-dbmliborder=<listofbackendnames>¶

Override order to check db backends for thedbm 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 thePY_COERCE_C_LOCALE macro.

SeePYTHONCOERCECLOCALE and thePEP 538.

--without-freelists¶

Disable all freelists except the empty tuple singleton.

Added in version 3.11.

--with-platlibdir=DIRNAME¶

Python library directory name (default islib).

Fedora and SuSE uselib64 on 64-bit platforms.

Seesys.platlibdir.

Added in version 3.9.

--with-wheel-pkg-dir=PATH¶

Directory of wheel packages used by theensurepip module(none by default).

Some Linux distribution packaging policies recommend against bundlingdependencies. For example, Fedora installs wheel packages in the/usr/share/python-wheels/ directory and don’t install theensurepip._bundled package.

Added in version 3.10.

--with-pkg-config=[check|yes|no]¶

Whether configure should usepkg-config to detect builddependencies.

• check (default):pkg-config is optional

• yes:pkg-config is mandatory

• no: configure does not usepkg-config even when present

Added in version 3.11.

--enable-pystats¶

Turn on internal statistics gathering.

The statistics will be dumped to a arbitrary (probably unique) file in/tmp/py_stats/, orC:\temp\py_stats\ on Windows. If that directorydoes not exist, results will be printed on stdout.

UseTools/scripts/summarize_stats.py to read the stats.

Added in version 3.11.

3.3.2.WebAssembly Options¶

--with-emscripten-target=[browser|node]¶

Set build flavor forwasm32-emscripten.

• browser (default): preload minimal stdlib, default MEMFS.

• node: NODERAWFS and pthread support.

Added in version 3.11.

--enable-wasm-dynamic-linking¶

Turn on dynamic linking support for WASM.

Dynamic linking enablesdlopen. File size of the executableincreases 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.

3.3.3.Install Options¶

--prefix=PREFIX¶

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

This value can be retrieved at runtime usingsys.prefix.

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

--exec-prefix=EPREFIX¶

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

This value can be retrieved at runtime usingsys.exec_prefix.

--disable-test-modules¶

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

Added in version 3.10.

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

Select theensurepip command run on Python installation:

• upgrade (default): runpython-mensurepip--altinstall--upgradecommand.

• install: runpython-mensurepip--altinstall command;

• no: don’t run ensurepip;

Added in version 3.6.

3.3.4.Performance options¶

Configuring Python using--enable-optimizations--with-lto (PGO + LTO) isrecommended for best performance. The experimental--enable-bolt flag canalso be used to improve performance.

--enable-optimizations¶

Enable Profile Guided Optimization (PGO) usingPROFILE_TASK(disabled by default).

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

Disable also semantic interposition in libpython if--enable-shared andGCC is used: add-fno-semantic-interposition to the compiler and linkerflags.

Note

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

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 forthe PGO generation task.

Default:-mtest--pgo--timeout=$(TESTTIMEOUT).

Added in version 3.8.

--with-lto=[full|thin|no|yes]¶

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

The C compiler Clang requiresllvm-ar for LTO (ar on macOS), as wellas an LTO-aware linker (ld.gold orlld).

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 theBOLT post-link binary optimizer (disabled bydefault).

BOLT is part of the LLVM project but is not always included in their binarydistributions. This flag requires thatllvm-bolt andmerge-fdataare available.

BOLT is still a fairly new project so this flag should be consideredexperimental for now. Because this tool operates on machine code its successis dependent on a combination of the build environment + the otheroptimization configure args + the CPU architecture, and not all combinationsare 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.

TheBOLT_INSTRUMENT_FLAGS andBOLT_APPLY_FLAGSconfigure variables can be defined to override the default set ofarguments forllvm-bolt to instrument and apply BOLT data tobinaries, respectively.

Added in version 3.12.

--with-computed-gotos¶

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

--without-pymalloc¶

Disable the specialized Python memory allocatorpymalloc(enabled by default).

See alsoPYTHONMALLOC environment variable.

--without-doc-strings¶

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

Don’t define theWITH_DOC_STRINGS macro.

See thePyDoc_STRVAR() macro.

--enable-profiling¶

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

--with-strict-overflow¶

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

3.3.5.Python Debug Build¶

A debug build is Python built with the--with-pydebug configureoption.

Effects of a debug build:

• Display all warnings by default: the list of default warning filters is emptyin thewarnings module.

• Addd tosys.abiflags.

• Addsys.gettotalrefcount() function.

• Add-Xshowrefcount command line option.

• Add-d command line option andPYTHONDEBUG environmentvariable to debug the parser.

• Add support for the__lltrace__ variable: enable low-level tracing in thebytecode evaluation loop if the variable is defined.

• Installdebug hooks on memory allocatorsto detect buffer overflow and other memory errors.

• DefinePy_DEBUG andPy_REF_DEBUG macros.

• Add runtime checks: code surrounded by#ifdefPy_DEBUG and#endif.Enableassert(...) and_PyObject_ASSERT(...) assertions: don’t settheNDEBUG macro (see also the--with-assertions configureoption). Main runtime checks:

  • Add sanity checks on the function arguments.

  • Unicode and int objects are created with their memory filled with a patternto detect usage of uninitialized objects.

  • Ensure that functions which can clear or replace the current exception arenot called with an exception raised.

  • Check that deallocator functions don’t change the current exception.

  • The garbage collector (gc.collect() function) runs some basic checkson objects consistency.

  • ThePy_SAFE_DOWNCAST() macro checks for integer underflow andoverflow when downcasting from wide types to narrow types.

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

3.3.6.Debug options¶

--with-pydebug¶

Build Python in debug mode: define thePy_DEBUGmacro (disabled by default).

--with-trace-refs¶

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

Effects:

• Define thePy_TRACE_REFS macro.

• Addsys.getobjects() function.

• AddPYTHONDUMPREFS environment variable.

This build is not ABI compatible with release build (default build) or debugbuild (Py_DEBUG andPy_REF_DEBUG macros).

Added in version 3.8.

--with-assertions¶

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

If set, theNDEBUG macro is not defined in theOPT compilervariable.

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).

SeeInstrumenting CPython with DTrace and SystemTap.

Added in version 3.6.

--with-address-sanitizer¶

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

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.

3.3.7.Linker options¶

--enable-shared¶

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

--without-static-libpython¶

Do not buildlibpythonMAJOR.MINOR.a and do not installpython.o(built and enabled by default).

Added in version 3.10.

3.3.8.Libraries options¶

--with-libs='lib1...'¶

Link against additional libraries (default is no).

--with-system-expat¶

Build thepyexpat module using an installedexpat library(default is no).

--with-system-libmpdec¶

Build the_decimal extension module using an installedmpdeclibrary, see thedecimal module (default is no).

Added in version 3.3.

--with-readline=editline¶

Useeditline library for backend of thereadline module.

Define theWITH_EDITLINE macro.

Added in version 3.10.

--without-readline¶

Don’t build thereadline module (built by default).

Don’t define theHAVE_LIBREADLINE macro.

Added in version 3.10.

--with-libm=STRING¶

Overridelibm math library toSTRING (default is system-dependent).

--with-libc=STRING¶

Overridelibc C library toSTRING (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 andpkg-config;

• DIR: set an explicit rpath.

Added in version 3.10.

3.3.9.Security Options¶

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

Select hash algorithm for use inPython/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 thessl module.

Added in version 3.7.

Changed in version 3.10:The settingspython andSTRING also set TLS 1.2 as minimumprotocol version.

3.3.10.macOS Options¶

SeeMac/README.rst.

--enable-universalsdk¶

--enable-universalsdk=SDKDIR¶

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

--enable-framework¶

--enable-framework=INSTALLDIR¶

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

--with-universal-archs=ARCH¶

Specify the kind of universal binary that should be created. This option isonly 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 arenot the same as theidentifiers used for universal binary wheels on macOS. See the PythonPackaging User Guide for details on thepackaging platform compatibilitytags 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).

3.3.11.Cross Compiling Options¶

Cross compiling, also known as cross building, can be used to build Pythonfor another CPU architecture or platform. Cross compiling requires a Pythoninterpreter for the build platform. The version of the build Python must matchthe version of the cross compiled host Python.

--build=BUILD¶

configure for building on BUILD, usually guessed byconfig.guess.

--host=HOST¶

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

--with-build-python=path/to/python¶

path to buildpython binary for cross compiling

Added in version 3.11.

CONFIG_SITE=file¶

An environment variable that points to a file with configure overrides.

Exampleconfig.site file:

# config.site-aarch64ac_cv_buggy_getaddrinfo=noac_cv_file__dev_ptmx=yesac_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

3.4.1.Main files of the build system¶

• configure.ac =>configure;

• Makefile.pre.in =>Makefile (created byconfigure);

• pyconfig.h (created byconfigure);

• Modules/Setup: C extensions built by the Makefile usingModule/makesetup shell script;

3.4.2.Main build steps¶

• C files (.c) are built as object files (.o).

• A staticlibpython library (.a) is created from objects files.

• python.o and the staticlibpython library are linked into thefinalpython program.

• C extensions are built by the Makefile (seeModules/Setup).

3.4.3.Main Makefile targets¶

• make: Build Python with the standard library.

• makeplatform:: build thepython program, but don’t build thestandard library extension modules.

• makeprofile-opt: build Python using Profile Guided Optimization (PGO).You can use the configure--enable-optimizations option to makethis the default target of themake command (makeall or justmake).

• makebuildbottest: Build Python and run the Python test suite, the sameway than buildbots test Python. SetTESTTIMEOUT variable (in seconds)to change the test timeout (1200 by default: 20 minutes).

• makeinstall: Build and install Python.

• makeregen-all: Regenerate (almost) all generated files;makeregen-stdlib-module-names andautoconf must be run separatelyfor the remaining generated files.

• makeclean: Remove built files.

• makedistclean: Same thanmakeclean, but remove also files createdby the configure script.

3.4.4.C extensions¶

Some C extensions are built as built-in modules, like thesys module.They are built with thePy_BUILD_CORE_BUILTIN macro defined.Built-in modules have no__file__ attribute:

>>>importsys>>>sys<module 'sys' (built-in)>>>>sys.__file__Traceback (most recent call last):  File"<stdin>", line1, 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 thePy_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.

ThePyAPI_FUNC(),PyAPI_DATA() andPyMODINIT_FUNC macros ofInclude/exports.h are defineddifferently depending if thePy_BUILD_CORE_MODULE macro is defined:

• UsePy_EXPORTED_SYMBOL if thePy_BUILD_CORE_MODULE is defined

• UsePy_IMPORTED_SYMBOL otherwise.

If thePy_BUILD_CORE_BUILTIN macro is used by mistake on a C extensionbuilt as a shared library, itsPyInit_xxx() function is not exported,causing anImportError on import.

3.5.1.Preprocessor flags¶

CONFIGURE_CPPFLAGS¶

Value ofCPPFLAGS variable passed to the./configure script.

Added in version 3.6.

CPPFLAGS¶

(Objective) C/C++ preprocessor flags, e.g.-Iinclude_dir if you haveheaders in a nonstandard directoryinclude_dir.

BothCPPFLAGS andLDFLAGS need to contain the shell’svalue to be able to build extension modules using thedirectories 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 Cextensions. Use it when a compiler flag shouldnot be part ofCFLAGS 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 inCFLAGS would take precedence over user- and package-supplied-Iflags.

• hardening flags such as-Werror because distributions cannot controlwhether packages installed by users conform to such heightenedstandards.

Added in version 3.5.

COMPILEALL_OPTS¶

Options passed to thecompileall command line when building PYC filesinmakeinstall. Default:-j0.

Added in version 3.12.

EXTRA_CFLAGS¶

Extra C compiler flags.

CONFIGURE_CFLAGS¶

Value ofCFLAGS variable passed to the./configurescript.

Added in version 3.2.

CONFIGURE_CFLAGS_NODIST¶

Value ofCFLAGS_NODIST variable passed to the./configurescript.

Added in version 3.5.

BASECFLAGS¶

Base compiler flags.

OPT¶

Optimization flags.

CFLAGS_ALIASING¶

Strict or non-strict aliasing flags used to compilePython/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 emptystring 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-inmodule, like theposix 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 likepython and_testembed.

Default:$(PURIFY)$(CC).

CONFIGURE_LDFLAGS¶

Value ofLDFLAGS variable passed to the./configure script.

Avoid assigningCFLAGS,LDFLAGS, etc. so users can usethem on the command line to append to these values without stomping thepre-set values.

Added in version 3.2.

LDFLAGS_NODIST¶

LDFLAGS_NODIST is used in the same manner asCFLAGS_NODIST. Use it when a linker flag shouldnot be part ofLDFLAGS 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 inLDFLAGS would take precedence over user- and package-supplied-Lflags.

CONFIGURE_LDFLAGS_NODIST¶

Value ofLDFLAGS_NODIST variable passed to the./configurescript.

Added in version 3.8.

LDFLAGS¶

Linker flags, e.g.-Llib_dir if you have libraries in a nonstandarddirectorylib_dir.

BothCPPFLAGS andLDFLAGS need to contain the shell’svalue to be able to build extension modules using thedirectories specified in the environment variables.

LIBS¶

Linker flags to pass libraries to the linker when linking the Pythonexecutable.

Example:-lrt.

LDSHARED¶

Command to build a shared library.

Default:@LDSHARED@$(PY_LDFLAGS).

BLDSHARED¶

Command to buildlibpython 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.