restore errno on success

Author: skirpichev

Lib/test/test_capi/test_complex.py

@@ -281,18 +281,33 @@ def test_py_c_abs(self):
         # Test _Py_c_abs()
         _py_c_abs = _testcapi._py_c_abs
 
-        self.assertEqual(_py_c_abs(-1), (1.0, 0))
-        self.assertEqual(_py_c_abs(1j), (1.0, 0))
-
-        self.assertEqual(_py_c_abs(complex('+inf+1j')), (INF, 0))
-        self.assertEqual(_py_c_abs(complex('-inf+1j')), (INF, 0))
-        self.assertEqual(_py_c_abs(complex('1.25+infj')), (INF, 0))
-        self.assertEqual(_py_c_abs(complex('1.25-infj')), (INF, 0))
-
-        self.assertTrue(isnan(_py_c_abs(complex('1.25+nanj'))[0]))
-        self.assertTrue(isnan(_py_c_abs(complex('nan-1j'))[0]))
-
-        self.assertEqual(_py_c_abs(complex(*[DBL_MAX]*2))[1], errno.ERANGE)
+        try:
+            _testcapi.set_errno(0)
+            self.assertEqual(_py_c_abs(-1), (1.0, 0))
+            _testcapi.set_errno(0)
+            self.assertEqual(_py_c_abs(1j), (1.0, 0))
+
+            _testcapi.set_errno(0)
+            self.assertEqual(_py_c_abs(complex('+inf+1j')), (INF, 0))
+            _testcapi.set_errno(0)
+            self.assertEqual(_py_c_abs(complex('-inf+1j')), (INF, 0))
+            _testcapi.set_errno(0)
+            self.assertEqual(_py_c_abs(complex('1.25+infj')), (INF, 0))
+            _testcapi.set_errno(0)
+            self.assertEqual(_py_c_abs(complex('1.25-infj')), (INF, 0))
+
+            _testcapi.set_errno(0)
+            self.assertTrue(isnan(_py_c_abs(complex('1.25+nanj'))[0]))
+            _testcapi.set_errno(0)
+            self.assertTrue(isnan(_py_c_abs(complex('nan-1j'))[0]))
+
+            _testcapi.set_errno(0)
+            self.assertEqual(_py_c_abs(complex(*[DBL_MAX]*2))[1], errno.ERANGE)
+
+            _testcapi.set_errno(errno.EACCES)  # preserve errno
+            self.assertEqual(_py_c_abs(1j), (1, errno.EACCES))
+        finally:
+            _testcapi.set_errno(0)
 
 
 if __name__ == "__main__":

Modules/_testcapi/complex.c

@@ -76,7 +76,6 @@ _py_c_abs(PyObject *Py_UNUSED(module), PyObject* obj)
         return NULL;
     }
 
-    errno = 0;
     res = _Py_c_abs(complex);
     return Py_BuildValue("di", res, errno);
 }

Objects/complexobject.c

@@ -381,27 +381,32 @@ _Py_c_abs(Py_complex z)
 {
     /* sets errno = ERANGE on overflow */
     double result;
+    int saved_errno = errno;
 
     if (!isfinite(z.real) || !isfinite(z.imag)) {
         /* C99 rules: if either the real or the imaginary part is an
            infinity, return infinity, even if the other part is a
            NaN. */
         if (isinf(z.real)) {
             result = fabs(z.real);
+            errno = saved_errno;
             return result;
         }
         if (isinf(z.imag)) {
             result = fabs(z.imag);
+            errno = saved_errno;
             return result;
         }
         /* either the real or imaginary part is a NaN,
            and neither is infinite. Result should be NaN. */
+        errno = saved_errno;
         return Py_NAN;
     }
     result = hypot(z.real, z.imag);
-    if (!isfinite(result)) {
+    if (!isfinite(result))
         errno = ERANGE;
-    }
+    else
+        errno = saved_errno;
     return result;
 }
 
@@ -811,11 +816,9 @@ complex_abs(PyObject *op)
     PyComplexObject *v = _PyComplexObject_CAST(op);
     double result;
 
-    result = hypot(v->cval.real, v->cval.imag);
-    /* Testing FE_OVERFLOW floating-point exception is slow. */
-    if (isfinite(v->cval.real) && isfinite(v->cval.imag)
-        && !isfinite(result))
-    {
+    errno = 0;
+    result = _Py_c_abs(v->cval);
+    if (errno == ERANGE) {
         PyErr_SetString(PyExc_OverflowError,
                         "absolute value too large");
         return NULL;