ENH: issue overflow warning when using `abs` on `np.int8(-128)` (#21648)

Checks condition a == NPY_MIN_@NAME@ to determine whether an overflow error has occurred for np.int8 type. See #21289 and #21188 (comment) for reference.

This also adds error integer overflow handling to the `-scalar` paths and "activates" a test for the unsigned versions.
A few tests are skipped, because the tests were buggy (they never ran).  These paths require followups to fix. 

3 files changed, 31 insertions, 7 deletions

diff --git a/numpy/core/src/umath/scalarmath.c.src b/numpy/core/src/umath/scalarmath.c.src
index 4993546f8..412f171ec 100644
--- a/numpy/core/src/umath/scalarmath.c.src
+++ b/numpy/core/src/umath/scalarmath.c.src
@@ -584,10 +584,15 @@ static NPY_INLINE int
 /**begin repeat
  * #name = byte, short, int, long, longlong#
  * #type = npy_byte, npy_short, npy_int, npy_long, npy_longlong#
+ * #NAME = BYTE, SHORT, INT, LONG, LONGLONG#
  */
 static NPY_INLINE int
 @name@_ctype_absolute(@type@ a, @type@ *out)
 {
+    if (a == NPY_MIN_@NAME@) {
+        *out = a;
+        return NPY_FPE_OVERFLOW;
+    }
     *out = (a < 0 ? -a : a);
     return 0;
 }
@@ -1564,8 +1569,23 @@ static PyObject *
 
 
     val = PyArrayScalar_VAL(a, @Name@);
+    int retstatus = @name@_ctype_@oper@(val, &out);
 
-    @name@_ctype_@oper@(val, &out);
+    if (retstatus) {
+        int bufsize, errmask;
+        PyObject *errobj;
+
+        if (PyUFunc_GetPyValues("@name@_scalars", &bufsize, &errmask,
+                                &errobj) < 0) {
+            return NULL;
+        }
+        int first = 1;
+        if (PyUFunc_handlefperr(errmask, errobj, retstatus, &first)) {
+            Py_XDECREF(errobj);
+            return NULL;
+        }
+        Py_XDECREF(errobj);
+    }
 
     /*
      * TODO: Complex absolute should check floating point flags.
diff --git a/numpy/core/tests/test_scalarmath.py b/numpy/core/tests/test_scalarmath.py
index b7fe5183e..57937a7a9 100644
--- a/numpy/core/tests/test_scalarmath.py
+++ b/numpy/core/tests/test_scalarmath.py
@@ -897,8 +897,11 @@ def test_scalar_integer_operation_overflow(dtype, operation):
 @pytest.mark.parametrize("dtype", np.typecodes["Integer"])
 @pytest.mark.parametrize("operation", [
         lambda min, neg_1: abs(min),
-        lambda min, neg_1: min * neg_1,
-        lambda min, neg_1: min // neg_1], ids=["abs", "*", "//"])
+        pytest.param(lambda min, neg_1: min * neg_1,
+            marks=pytest.mark.xfail(reason="broken on some platforms")),
+        pytest.param(lambda min, neg_1: min // neg_1,
+            marks=pytest.mark.skip(reason="broken on some platforms"))],
+        ids=["abs", "*", "//"])
 def test_scalar_signed_integer_overflow(dtype, operation):
     # The minimum signed integer can "overflow" for some additional operations
     st = np.dtype(dtype).type
@@ -910,8 +913,7 @@ def test_scalar_signed_integer_overflow(dtype, operation):
 
 
 @pytest.mark.parametrize("dtype", np.typecodes["UnsignedInteger"])
-@pytest.mark.xfail  # TODO: the check is quite simply missing!
-def test_scalar_signed_integer_overflow(dtype):
+def test_scalar_unsigned_integer_overflow(dtype):
     val = np.dtype(dtype).type(8)
     with pytest.warns(RuntimeWarning, match="overflow encountered"):
         -val
diff --git a/numpy/typing/tests/data/pass/arithmetic.py b/numpy/typing/tests/data/pass/arithmetic.py
index 4ed69c923..07a990127 100644
--- a/numpy/typing/tests/data/pass/arithmetic.py
+++ b/numpy/typing/tests/data/pass/arithmetic.py
@@ -2,6 +2,7 @@ from __future__ import annotations
 
 from typing import Any
 import numpy as np
+import pytest
 
 c16 = np.complex128(1)
 f8 = np.float64(1)
@@ -330,8 +331,9 @@ AR_O **= AR_LIKE_O
 -f4
 -i8
 -i4
--u8
--u4
+with pytest.warns(RuntimeWarning):
+    -u8
+    -u4
 -td
 -AR_f