sagemath#34997: Fix bug in conversion from python int to ZZ (python 3…

….11, 32 bit)

This affects 32 bit architectures, where the representation of python
integers changed in cpython 3.11, when compiled with gcc12.

As part of sagemath#33842, the function `sage.arith.long.integer_check_long_py()`
was rewritten to support the new representation.  Unfortunately a bug
remained that triggers UB for the conversion of integers between 2^60
and 2^63-1. Alas, the undesired behaviour does not happen with gcc10;
it only started when I switched to gcc12.

The bug manifests in lots of doctests failing, but a quick way to
demonstrate the issue is

    sage: ZZ ( int(1152921504606847018) )  # 2^60 + 42
    42

The function `integer_check_long_py()` has good unit testing, checking
values around the word size, but this range was missing.

This commit adds a simple fix and new test cases for a few integers in
this range.

Technical explanation:

The UB is in the line

    cdef long lead_3_overflow = (<long>1) << (BITS_IN_LONG - 2 * PyLong_SHIFT)

In our case we have `BITS_IN_LONG == 31` and `PyLong_SHIFT == 30` so the
computed value is `<long>1 << -29` which is UB and it happens to
evaluate to 0 with gcc10 but 8 with gcc12.

The solution is to set the value to 0 when `BITS_IN_LONG < 2 * PyLong_SHIFT`.

src/sage/arith/long.pxd

@@ -270,6 +270,17 @@ cdef inline bint integer_check_long_py(x, long* value, int* err):
         sage: L += [-x for x in L] + [0, long_min()]
         sage: for v in L:
         ....:     assert check_long_py(int(v)) == v
+        sage: check_long_py(int(2^60))
+        1152921504606846976                 # 64-bit
+        'Overflow (...)'                    # 32-bit
+        sage: check_long_py(int(2^61))
+        2305843009213693952                 # 64-bit
+        'Overflow (...)'                    # 32-bit
+        sage: check_long_py(int(2^62))
+        4611686018427387904                 # 64-bit
+        'Overflow (...)'                    # 32-bit
+        sage: check_long_py(int(2^63))
+        'Overflow (...)'
         sage: check_long_py(int(2^100))
         'Overflow (...)'
         sage: check_long_py(int(long_max() + 1))
@@ -310,6 +321,9 @@ cdef inline bint integer_check_long_py(x, long* value, int* err):
     cdef long lead
     cdef long lead_2_overflow = (<long>1) << (BITS_IN_LONG - PyLong_SHIFT)
     cdef long lead_3_overflow = (<long>1) << (BITS_IN_LONG - 2 * PyLong_SHIFT)
+    if BITS_IN_LONG < 2 * PyLong_SHIFT:
+        # in this case 3 digit is always overflow
+        lead_3_overflow = 0
     if size == 0:
         value[0] = 0
         err[0] = 0