gh-91246: Implement PEP 775: Make zlib required on platforms other than wasi

Doc/whatsnew/3.14.rst

@@ -1310,6 +1310,12 @@ Build changes
 * GNU Autoconf 2.72 is now required to generate :file:`configure`.
   (Contributed by Erlend Aasland in :gh:`115765`.)
 
+* zlib is now officially required to build CPython.
+  It is still technically possible to build CPython without it for special needs, like bootstrapping.
+  Such builds are not supported, but we can accept pull requests to keep them working.
+  As an exception, zlib is not required on WASI.
+  (Contributed by Stan Ulbrych in :gh:`130297`.)
+
 .. _whatsnew314-pep761:
 
 PEP 761: Discontinuation of PGP signatures

Lib/encodings/zlib_codec.py

@@ -6,7 +6,7 @@
 """
 
 import codecs
-import zlib # this codec needs the optional zlib module !
+import zlib
 
 ### Codec APIs
 

Lib/shutil.py

@@ -11,12 +11,6 @@
 import collections
 import errno
 
-try:
-    import zlib
-    del zlib
-    _ZLIB_SUPPORTED = True
-except ImportError:
-    _ZLIB_SUPPORTED = False
 
 try:
     import bz2
@@ -1000,7 +994,7 @@ def _make_tarball(base_name, base_dir, compress="gzip", verbose=0, dry_run=0,
     """
     if compress is None:
         tar_compression = ''
-    elif _ZLIB_SUPPORTED and compress == 'gzip':
+    elif compress == 'gzip':
         tar_compression = 'gz'
     elif _BZ2_SUPPORTED and compress == 'bzip2':
         tar_compression = 'bz2'
@@ -1121,10 +1115,9 @@ def _make_zipfile(base_name, base_dir, verbose=0, dry_run=0,
               "uncompressed tar file"),
 }
 
-if _ZLIB_SUPPORTED:
-    _ARCHIVE_FORMATS['gztar'] = (_make_tarball, [('compress', 'gzip')],
-                                "gzip'ed tar-file")
-    _ARCHIVE_FORMATS['zip'] = (_make_zipfile, [], "ZIP file")
+_ARCHIVE_FORMATS['gztar'] = (_make_tarball, [('compress', 'gzip')],
+                            "gzip'ed tar-file")
+_ARCHIVE_FORMATS['zip'] = (_make_zipfile, [], "ZIP file")
 
 if _BZ2_SUPPORTED:
     _ARCHIVE_FORMATS['bztar'] = (_make_tarball, [('compress', 'bzip2')],
@@ -1345,12 +1338,9 @@ def _unpack_tarfile(filename, extract_dir, *, filter=None):
 _UNPACK_FORMATS = {
     'tar':   (['.tar'], _unpack_tarfile, [], "uncompressed tar file"),
     'zip':   (['.zip'], _unpack_zipfile, [], "ZIP file"),
+    'gztar': (['.tar.gz', '.tgz'], _unpack_tarfile, [], "gzip'ed tar-file"),
 }
 
-if _ZLIB_SUPPORTED:
-    _UNPACK_FORMATS['gztar'] = (['.tar.gz', '.tgz'], _unpack_tarfile, [],
-                                "gzip'ed tar-file")
-
 if _BZ2_SUPPORTED:
     _UNPACK_FORMATS['bztar'] = (['.tar.bz2', '.tbz2'], _unpack_tarfile, [],
                                 "bzip2'ed tar-file")

Lib/tarfile.py

@@ -364,10 +364,7 @@ def __init__(self, name, mode, comptype, fileobj, bufsize,
 
         try:
             if comptype == "gz":
-                try:
-                    import zlib
-                except ImportError:
-                    raise CompressionError("zlib module is not available") from None
+                import zlib
                 self.zlib = zlib
                 self.crc = zlib.crc32(b"")
                 if mode == "r":
@@ -2697,13 +2694,10 @@ def next(self):
             except SubsequentHeaderError as e:
                 raise ReadError(str(e)) from None
             except Exception as e:
-                try:
-                    import zlib
-                    if isinstance(e, zlib.error):
-                        raise ReadError(f'zlib error: {e}') from None
-                    else:
-                        raise e
-                except ImportError:
+                import zlib
+                if isinstance(e, zlib.error):
+                    raise ReadError(f'zlib error: {e}') from None
+                else:
                     raise e
             break
 

Lib/test/test_zlib.py

@@ -7,9 +7,22 @@
 import random
 import sys
 from test.support import bigmemtest, _1G, _4G, is_s390x
+import importlib
 
-
-zlib = import_helper.import_module('zlib')
+# Building CPython without zlib is not supported except WASI.
+#
+# Anyone who wants build CPython this way should be prepared to patch it,
+# but the core team may help getting those patches to the main branch
+# (as that’s the place where multiple third parties can cooperate).
+#
+# For tests to pass without zlib, this file needs to be removed.
+
+try:
+    zlib = importlib.import_module('zlib')
+except ImportError as msg:
+    if sys.platform.startswith('wasi'):
+        raise unittest.SkipTest(str(msg))
+    raise ImportError("Building CPython without zlib is not supported")
 
 requires_Compress_copy = unittest.skipUnless(
         hasattr(zlib.compressobj(), "copy"),

Lib/zipfile/__init__.py

@@ -14,12 +14,8 @@
 import threading
 import time
 
-try:
-    import zlib # We may need its compression method
-    crc32 = zlib.crc32
-except ImportError:
-    zlib = None
-    crc32 = binascii.crc32
+import zlib
+crc32 = zlib.crc32
 
 try:
     import bz2 # We may need its compression method
@@ -771,12 +767,8 @@ def decompress(self, data):
 }
 
 def _check_compression(compression):
-    if compression == ZIP_STORED:
+    if compression in (ZIP_STORED, ZIP_DEFLATED):
         pass
-    elif compression == ZIP_DEFLATED:
-        if not zlib:
-            raise RuntimeError(
-                "Compression requires the (missing) zlib module")
     elif compression == ZIP_BZIP2:
         if not bz2:
             raise RuntimeError(

Lib/zipimport.py

@@ -604,9 +604,7 @@ def _read_directory(archive):
 
 _importing_zlib = False
 
-# Return the zlib.decompress function object, or NULL if zlib couldn't
-# be imported. The function is cached when found, so subsequent calls
-# don't import zlib again.
+# Return the zlib.decompress function object or raise an import error.
 def _get_decompress_func():
     global _importing_zlib
     if _importing_zlib:
@@ -618,9 +616,6 @@ def _get_decompress_func():
     _importing_zlib = True
     try:
         from zlib import decompress
-    except Exception:
-        _bootstrap._verbose_message('zipimport: zlib UNAVAILABLE')
-        raise ZipImportError("can't decompress data; zlib not available")
     finally:
         _importing_zlib = False
 

Misc/NEWS.d/next/Build/2025-02-19-00-00-00.gh-issue-91246.ahsgd3.rst

@@ -0,0 +1,2 @@
+Make zlib required to build CPython with the exception of WASI.
+(Contributed by Stan Ulbrych in :gh:`130297`.)

Modules/binascii.c

@@ -60,7 +60,7 @@
 #include "Python.h"
 #include "pycore_long.h"          // _PyLong_DigitValue
 #include "pycore_strhex.h"        // _Py_strhex_bytes_with_sep()
-#ifdef USE_ZLIB_CRC32
+#ifndef NO_ZLIB_CRC32
 #  include "zlib.h"
 #endif
 
@@ -616,7 +616,7 @@ binascii_crc_hqx_impl(PyObject *module, Py_buffer *data, unsigned int crc)
     return PyLong_FromUnsignedLong(crc);
 }
 
-#ifndef USE_ZLIB_CRC32
+#ifdef NO_ZLIB_CRC32
 /*  Crc - 32 BIT ANSI X3.66 CRC checksum files
     Also known as: ISO 3307
 **********************************************************************|
@@ -749,7 +749,7 @@ internal_crc32(const unsigned char *bin_data, Py_ssize_t len, unsigned int crc)
     result = (crc ^ 0xFFFFFFFF);
     return result & 0xffffffff;
 }
-#endif  /* USE_ZLIB_CRC32 */
+#endif  /* NO_ZLIB_CRC32 */
 
 /*[clinic input]
 binascii.crc32 -> unsigned_int
@@ -765,9 +765,11 @@ static unsigned int
 binascii_crc32_impl(PyObject *module, Py_buffer *data, unsigned int crc)
 /*[clinic end generated code: output=52cf59056a78593b input=bbe340bc99d25aa8]*/
 
-#ifdef USE_ZLIB_CRC32
+#ifndef NO_ZLIB_CRC32
 /* This is the same as zlibmodule.c zlib_crc32_impl. It exists in two
- * modules for historical reasons. */
+ * modules for historical reasons. They should be consolidated in the future
+ * once WASI supports zlib.
+ */
 {
     /* Releasing the GIL for very small buffers is inefficient
        and may lower performance */
@@ -798,7 +800,7 @@ binascii_crc32_impl(PyObject *module, Py_buffer *data, unsigned int crc)
     }
     return crc & 0xffffffff;
 }
-#else  /* USE_ZLIB_CRC32 */
+#else  /* NO_ZLIB_CRC32 */
 {
     const unsigned char *bin_data = data->buf;
     Py_ssize_t len = data->len;
@@ -815,7 +817,7 @@ binascii_crc32_impl(PyObject *module, Py_buffer *data, unsigned int crc)
         return internal_crc32(bin_data, len, crc);
     }
 }
-#endif  /* USE_ZLIB_CRC32 */
+#endif  /* NO_ZLIB_CRC32 */
 
 /*[clinic input]
 binascii.b2a_hex

PCbuild/pythoncore.vcxproj

@@ -457,9 +457,7 @@
     <ClCompile Include="..\Modules\_weakref.c" />
     <ClCompile Include="..\Modules\arraymodule.c" />
     <ClCompile Include="..\Modules\atexitmodule.c" />
-    <ClCompile Include="..\Modules\binascii.c">
-      <PreprocessorDefinitions>USE_ZLIB_CRC32;%(PreprocessorDefinitions)</PreprocessorDefinitions>
-    </ClCompile>
+    <ClCompile Include="..\Modules\binascii.c" />
     <ClCompile Include="..\Modules\cmathmodule.c" />
     <ClCompile Include="..\Modules\_datetimemodule.c" />
     <ClCompile Include="..\Modules\errnomodule.c" />

configure.ac

@@ -5323,14 +5323,10 @@ if test "$ac_cv_have_lchflags" = yes ; then
 fi
 
 dnl Check for compression libraries
-AH_TEMPLATE([HAVE_ZLIB_COPY], [Define if the zlib library has inflateCopy])
-
-dnl detect zlib from Emscripten emport
-PY_CHECK_EMSCRIPTEN_PORT([ZLIB], [-sUSE_ZLIB])
+AH_TEMPLATE([HAVE_ZLIB_COPY], [Define if the zlib library has inflateCopy; zlib 1.2.0 (2003) added inflateCopy.])
 
 PKG_CHECK_MODULES([ZLIB], [zlib >= 1.2.0], [
   have_zlib=yes
-  dnl zlib 1.2.0 (2003) added inflateCopy
   AC_DEFINE([HAVE_ZLIB_COPY], [1])
 ], [
   WITH_SAVE_ENV([
@@ -5346,12 +5342,23 @@ PKG_CHECK_MODULES([ZLIB], [zlib >= 1.2.0], [
     ])
   ])
 ])
-
-dnl binascii can use zlib for optimized crc32.
-AS_VAR_IF([have_zlib], [yes], [
-  BINASCII_CFLAGS="-DUSE_ZLIB_CRC32 $ZLIB_CFLAGS"
-  BINASCII_LIBS="$ZLIB_LIBS"
-])
+dnl temporarily throw only errors on builds other than wasi until wasi supports zlib
+AS_CASE([$ac_sys_system],
+  [WASI], [
+    BINASCII_CFLAGS="-DNO_ZLIB_CRC32"
+    BINASCII_LIBS=""
+  ],
+  [*], [
+    if test "$have_zlib" != "yes"; then
+      AC_MSG_ERROR([m4_normalize([
+        zlib.h and libz are required. Install your OS's zlib-devel or
+        zlib1g-dev equivalent library or get it from https://zlib.net/.
+      ])])
+    fi
+    BINASCII_CFLAGS="$ZLIB_CFLAGS"
+    BINASCII_LIBS="$ZLIB_LIBS"
+  ]
+)
 
 dnl detect bzip2 from Emscripten emport
 PY_CHECK_EMSCRIPTEN_PORT([BZIP2], [-sUSE_BZIP2])

pyconfig.h.in

@@ -1609,7 +1609,8 @@
 /* Define to 1 if you have the 'writev' function. */
 #undef HAVE_WRITEV
 
-/* Define if the zlib library has inflateCopy */
+/* Define if the zlib library has inflateCopy; zlib 1.2.0 (2003) added
+   inflateCopy. */
 #undef HAVE_ZLIB_COPY
 
 /* Define to 1 if you have the <zlib.h> header file. */