Issue #25626: Change zlib to accept Py_ssize_t and cap to UINT_MAX

The underlying zlib library stores sizes in “unsigned int”. The corresponding
Python parameters are all sizes of buffers filled in by zlib, so it is okay
to reduce higher values to the UINT_MAX internal cap. OverflowError is still
raised for sizes that do not fit in Py_ssize_t.

Sizes are now limited to Py_ssize_t rather than unsigned long, because Python
byte strings cannot be larger than Py_ssize_t. Previously this could result
in a SystemError on 32-bit platforms.

This resolves a regression in the gzip module when reading more than UINT_MAX
or LONG_MAX bytes in one call, introduced by revision 62723172412c.

1 files changed, 4 insertions, 4 deletions

diff --git a/Modules/clinic/zlibmodule.c.h b/Modules/clinic/zlibmodule.c.h
index 35661a5..c5cdf42 100644
--- a/Modules/clinic/zlibmodule.c.h
+++ b/Modules/clinic/zlibmodule.c.h
@@ -68,7 +68,7 @@ zlib_decompress(PyModuleDef *module, PyObject *args)
     unsigned int bufsize = DEF_BUF_SIZE;
 
     if (!PyArg_ParseTuple(args, "y*|iO&:decompress",
-        &data, &wbits, uint_converter, &bufsize))
+        &data, &wbits, capped_uint_converter, &bufsize))
         goto exit;
     return_value = zlib_decompress_impl(module, &data, wbits, bufsize);
 
@@ -242,7 +242,7 @@ zlib_Decompress_decompress(compobject *self, PyObject *args)
     unsigned int max_length = 0;
 
     if (!PyArg_ParseTuple(args, "y*|O&:decompress",
-        &data, uint_converter, &max_length))
+        &data, capped_uint_converter, &max_length))
         goto exit;
     return_value = zlib_Decompress_decompress_impl(self, &data, max_length);
 
@@ -353,7 +353,7 @@ zlib_Decompress_flush(compobject *self, PyObject *args)
     unsigned int length = DEF_BUF_SIZE;
 
     if (!PyArg_ParseTuple(args, "|O&:flush",
-        uint_converter, &length))
+        capped_uint_converter, &length))
         goto exit;
     return_value = zlib_Decompress_flush_impl(self, length);
 
@@ -438,4 +438,4 @@ exit:
 #ifndef ZLIB_COMPRESS_COPY_METHODDEF
     #define ZLIB_COMPRESS_COPY_METHODDEF
 #endif /* !defined(ZLIB_COMPRESS_COPY_METHODDEF) */
-/*[clinic end generated code: output=56ed1147bbbb4788 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=7734aec079550bc8 input=a9049054013a1b77]*/