3. Python を構成する
********************


3.1. 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 "ssl" and "hashlib" modules.

* On Windows, Microsoft Visual Studio 2017 or later is required.

バージョン 3.5 で変更: On Windows, Visual Studio 2015 or later is
required.

バージョン 3.6 で変更: Selected C99 features are now required, like
"<stdint.h>" and "static inline" functions.

バージョン 3.7 で変更: Thread support and OpenSSL 1.0.2 are now
required.

バージョン 3.10 で変更: OpenSSL 1.1.1 is now required.

バージョン 3.11 で変更: C11 compiler, IEEE 754 and NaN support are now
required. On Windows, Visual Studio 2017 or later is required.

See also **PEP 7** "Style Guide for C Code" and **PEP 11** "CPython
platform support".


3.2. 生成されるファイル
=======================

To reduce build dependencies, Python source code contains multiple
generated files. Commands to regenerate all generated files:

   make regen-all
   make regen-stdlib-module-names
   make regen-limited-abi
   make regen-configure

The "Makefile.pre.in" file documents generated files, their inputs,
and tools used to regenerate them. Search for "regen-*" make targets.


3.2.1. 構成スクリプト
---------------------

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 "autoconf-
archive", "aclocal" and "pkg-config" versions.


3.3. Configureオプション
========================

List all "./configure" script options using:

   ./configure --help

Pythonのソース配布の中の "Misc/SpecialBuilds.txt" も参照してください。


3.3.1. 一般的なオプション
-------------------------

--enable-loadable-sqlite-extensions

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

   "sqlite3" モジュールの "sqlite3.Connection.enable_load_extension()"
   メソッドを参照してください。

   Added in version 3.6.

--disable-ipv6

   IPv6サポートを無効にします(サポートされている場合はデフォルトで有効
   )、 "socket" モジュールを参照してください。

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

   Python "int" の桁の大きさをビット単位で定義します: 15ビットまたは30
   ビットです。

   デフォルトでは、桁の大きさは30です。

   "PYLONG_BITS_IN_DIGIT" を "15" または "30" に定義します。

   "sys.int_info.bits_per_digit" を参照してください。

--with-suffix=SUFFIX

   Python の実行ファイルの接頭辞を *SUFFIX* に設定します。

   デフォルトの接尾辞は、 Windows と macOS では ".exe" ( "python.exe"
   実行ファイル)、 Emscripten node では ".js" 、 Emscripten browser で
   は ".html" 、 WASI では ".wasm" 、その他のプラットフォームでは空文
   字列になります ( "python" 実行ファイル)。

   バージョン 3.11 で変更: WASM プラットフォームのデフォルトの接頭辞は
   、 ".js" 、 ".html" 、 ".wasm" のうちの1つです。

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

   デフォルトのタイムゾーン検索パスを "zoneinfo.TZPATH" に設定します。
   "zoneinfo" モジュールの Compile-time configuration を参照してくださ
   い。

   デフォルト: "/usr/share/zoneinfo:/usr/lib/zoneinfo:/usr/share/lib/
   zoneinfo:/etc/zoneinfo"

   "os.pathsep" パスセパレータを参照してください。

   Added in version 3.9.

--without-decimal-contextvar

   コルーチンローカルコンテキスト(デフォルト)ではなく、スレッドローカ
   ルコンテキストを使用して "_decimal" 拡張モジュールをビルドします。
   "decimal" モジュールを参照してください。

   "decimal.HAVE_CONTEXTVAR" および "contextvars" モジュールを参照して
   ください。

   Added in version 3.9.

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

   "dbm" モジュールの DB バックエンドをチェックする順序をオーバーライ
   ドします。

   有効な値は、バックエンド名をコロン( ":" )で区切った文字列です:

   * "ndbm";

   * "gdbm";

   * "bdb"。

--without-c-locale-coercion

   UTF-8 ベースのロケールへの C ロケールの強制を無効にします(デフォル
   トで有効)。

   "PY_COERCE_C_LOCALE" マクロは定義しないでください。

   "PYTHONCOERCECLOCALE" および **PEP 538** を参照してください。

--without-freelists

   Disable all freelists except the empty tuple singleton.

   Added in version 3.11.

--with-platlibdir=DIRNAME

   Python のライブラリディレクトリ名(デフォルトは "lib" )。

   Fedora と SuSE は64ビットプラットフォームで "lib64" を使用します。

   "sys.platlibdir" を参照してください。

   Added in version 3.9.

--with-wheel-pkg-dir=PATH

   "ensurepip" モジュールが使用する wheel パッケージのディレクトリです
   (デフォルトはなし)。

   Linux ディストリビューションのパッケージングポリシーの中には、依存
   関係をバンドルすることを推奨しているものがあります。例えば、 Fedora
   は wheel パッケージを "/usr/share/python-wheels/" ディレクトリにイ
   ンストールし、 "ensurepip._bundled" パッケージはインストールしませ
   ん。

   Added in version 3.10.

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

   configure がビルドの依存関係を検出するために **pkg-config** を使用
   するかどうかを設定します。

   * "check" (デフォルト): **pkg-config** はオプションです。

   * "yes" : **pkg-config** は必須です。

   * "no" : **pkg-config** が存在しても、 configure は使用しません。

   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/", or "C:\temp\py_stats\" on Windows. If that
   directory does not exist, results will be printed on stdout.

   統計情報を読むには "Tools/scripts/summarize_stats.py" を使用してく
   ださい。

   Added in version 3.11.


3.3.2. WebAssembly オプション
-----------------------------

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

   "wasm32-emscripten" のビルドフレーバーを設定します。

   * "browser" (デフォルト): 最小限の stdlib 、デフォルトの MEMFS をプ
     リロードします。

   * "node": NODERAWFS と pthread をサポートします。

   Added in version 3.11.

--enable-wasm-dynamic-linking

   WASM のダイナミックリンクサポートをオンにします。

   ダイナミックリンクにより "dlopen" が可能になります。デッドコードの
   排除や機能追加に制限があるため、実行ファイルのファイルサイズが大き
   くなります。

   Added in version 3.11.

--enable-wasm-pthreads

   WASM の pthreads サポートをオンにします。

   Added in version 3.11.


3.3.3. インストールオプション
-----------------------------

--prefix=PREFIX

   アーキテクチャに依存しないファイルを PREFIX にインストールします。
   Unix の場合、デフォルトは "/usr/local" です。

   この値は、実行時に "sys.prefix" を使って取得することができます。

   例として、 "--prefix="$HOME/.local/"" を使用すると、 Python をその
   ホームディレクトリにインストールすることができます。

--exec-prefix=EPREFIX

   アーキテクチャ依存のファイルを EPREFIX にインストールします。デフォ
   ルトは "--prefix" です。

   この値は、実行時に "sys.exec_prefix" を使って取得することができます
   。

--disable-test-modules

   "test" パッケージや "_testcapi" 拡張モジュール(デフォルトでビルド、
   インストールされます)のようなテストモジュールをビルド、インストール
   しないようにします。

   Added in version 3.10.

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

   Python のインストール時に実行される "ensurepip" コマンドを選択しま
   す:

   * "upgrade" (デフォルト): "python -m ensurepip --altinstall
     --upgrade" コマンドを実行します。

   * "install": "python -m ensurepip --altinstall" コマンドを実行しま
     す。

   * "no": ensurepip を実行しない;

   Added in version 3.6.


3.3.4. パフォーマンスに関するオプション
---------------------------------------

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

   "PROFILE_TASK" を使用して Profile Guided Optimization (PGO) を有効
   にします(デフォルトでは無効です)。

   Cコンパイラの Clang では、 PGO のために "llvm-profdata" プログラム
   が必要です。macOS では、 GCC もこれを必要とします: GCC は macOS の
   Clang のエイリアスにすぎません。

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

   注釈:

     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.

   バージョン 3.10 で変更: GCC で "-fno-semantic-interposition" を使用
   する。

PROFILE_TASK

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

   デフォルト: "-m test --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 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.

   バージョン 3.12 で変更: 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.

--with-computed-gotos

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

--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).


3.3.5. 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.

バージョン 3.8 で変更: Release builds and debug builds are now ABI
compatible: defining the "Py_DEBUG" macro no longer implies the
"Py_TRACE_REFS" macro (see the "--with-trace-refs" option), which
introduces the only ABI incompatibility.


3.3.6. 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.

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

   Added in version 3.8.

--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).

   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 build "libpythonMAJOR.MINOR.a" and do not install "python.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 the "pyexpat" module using an installed "expat" library
   (default is no).

--with-system-libmpdec

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

   Added in version 3.3.

--with-readline=editline

   Use "editline" library for backend of the "readline" module.

   Define the "WITH_EDITLINE" macro.

   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.


3.3.9. 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.

   バージョン 3.10 で変更: The settings "python" and *STRING* also set
   TLS 1.2 as minimum protocol version.


3.3.10. macOS のオプション
--------------------------

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.

   オプション:

   * "universal2";

   * "32-bit";

   * "64-bit";

   * "3-way";

   * "intel";

   * "intel-32";

   * "intel-64";

   * "all"。

--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. クロスコンパイルのオプション
------------------------------------

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

クロスコンパイルの例:

   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. Python Build System
========================


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
----------------------------

* "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 "--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.


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. Compiler and linker flags
==============================

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


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. "-I*include_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. "-L*lib_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.
