gh-133489: Remove size restrictions on getrandbits() and randbytes()

random.getrandbits() can now generate more that 2**31 bits.
random.randbytes() can now generate more that 256 MiB.

Author: serhiy-storchaka

Lib/test/test_random.py

@@ -806,6 +806,20 @@ def test_getrandbits(self):
         self.assertEqual(self.gen.getrandbits(100),
                          97904845777343510404718956115)
 
+    def test_getrandbits_2G_bits(self):
+        self.gen.seed(1234567)
+        x = self.gen.getrandbits(2**31)
+        self.assertEqual(x.bit_length(), 2**31)
+        self.assertEqual(x >> (2**31-100), 1226514312032729439655761284440)
+        self.assertEqual(x & (2**100-1), 890186470919986886340158459475)
+
+    def test_getrandbits_4G_bits(self):
+        self.gen.seed(1234568)
+        x = self.gen.getrandbits(2**32)
+        self.assertEqual(x.bit_length(), 2**32)
+        self.assertEqual(x >> (2**32-100), 739728759900339699429794460738)
+        self.assertEqual(x & (2**100-1), 287241425661104632871036099814)
+
     def test_randrange_uses_getrandbits(self):
         # Verify use of getrandbits by randrange
         # Use same seed as in the cross-platform repeatability test

Misc/NEWS.d/next/Library/2025-05-08-13-43-19.gh-issue-133489.9eGS1Z.rst

@@ -0,0 +1,2 @@
+:func:`random.getrandbits` can now generate more that 2\ :sup:`31` bits.
+:func:`random.randbytes` can now generate more that 256 MiB.

Modules/_randommodule.c

@@ -497,34 +497,32 @@ _random_Random_setstate_impl(RandomObject *self, PyObject *state)
 _random.Random.getrandbits
 
   self: self(type="RandomObject *")
-  k: int
+  k: uint64
   /
 
 getrandbits(k) -> x.  Generates an int with k random bits.
 [clinic start generated code]*/
 
 static PyObject *
-_random_Random_getrandbits_impl(RandomObject *self, int k)
-/*[clinic end generated code: output=b402f82a2158887f input=87603cd60f79f730]*/
+_random_Random_getrandbits_impl(RandomObject *self, uint64_t k)
+/*[clinic end generated code: output=c30ef8435f3433cf input=64226ac13bb4d2a3]*/
 {
-    int i, words;
+    Py_ssize_t i, words;
     uint32_t r;
     uint32_t *wordarray;
     PyObject *result;
 
-    if (k < 0) {
-        PyErr_SetString(PyExc_ValueError,
-                        "number of bits must be non-negative");
-        return NULL;
-    }
-
     if (k == 0)
         return PyLong_FromLong(0);
 
     if (k <= 32)  /* Fast path */
         return PyLong_FromUnsignedLong(genrand_uint32(self) >> (32 - k));
 
-    words = (k - 1) / 32 + 1;
+    if ((k - 1u) / 32u + 1u > PY_SSIZE_T_MAX / 4u) {
+        PyErr_NoMemory();
+        return NULL;
+    }
+    words = (k - 1u) / 32u + 1u;
     wordarray = (uint32_t *)PyMem_Malloc(words * 4);
     if (wordarray == NULL) {
         PyErr_NoMemory();