gh-119771: Set errno on overflows in _Py_c_pow() (#120256)

skirpichev · web-flow · commit 8a284e189673 · 2024-09-18T10:39:11.000+02:00
Before we did this in complex_pow() and behavior of the public C API
function _Py_c_pow() was different from the pure-python pow().
diff --git a/Doc/c-api/complex.rst b/Doc/c-api/complex.rst
@@ -79,6 +79,8 @@ pointers.  This is consistent throughout the API.
    If *num* is null and *exp* is not a positive real number,
    this method returns zero and sets :c:data:`errno` to :c:macro:`!EDOM`.
 
+   Set :c:data:`errno` to :c:macro:`!ERANGE` on overflows.
+
 
 Complex Numbers as Python Objects
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/Lib/test/test_capi/test_complex.py b/Lib/test/test_capi/test_complex.py
@@ -226,7 +226,11 @@ def test_py_c_pow(self):
 
         self.assertEqual(_py_c_pow(0j, -1)[1], errno.EDOM)
         self.assertEqual(_py_c_pow(0j, 1j)[1], errno.EDOM)
-        self.assertEqual(_py_c_pow(*[DBL_MAX+1j]*2)[0], complex(*[INF]*2))
+        max_num = DBL_MAX+1j
+        self.assertEqual(_py_c_pow(max_num, max_num),
+                         (complex(INF, INF), errno.ERANGE))
+        self.assertEqual(_py_c_pow(max_num, 2),
+                         (complex(INF, INF), errno.ERANGE))
 
 
     def test_py_c_abs(self):
diff --git a/Misc/NEWS.d/next/C API/2024-06-08-08-33-40.gh-issue-119771.Oip2dL.rst b/Misc/NEWS.d/next/C API/2024-06-08-08-33-40.gh-issue-119771.Oip2dL.rst
@@ -0,0 +1,2 @@
+Set :data:`errno` in :c:func:`_Py_c_pow` on overflows.  Patch by Sergey B
+Kirpichev.
diff --git a/Objects/complexobject.c b/Objects/complexobject.c
@@ -173,6 +173,8 @@ _Py_c_pow(Py_complex a, Py_complex b)
         }
         r.real = len*cos(phase);
         r.imag = len*sin(phase);
+
+        _Py_ADJUST_ERANGE2(r.real, r.imag);
     }
     return r;
 }
@@ -567,12 +569,12 @@ complex_pow(PyObject *v, PyObject *w, PyObject *z)
     // a faster and more accurate algorithm.
     if (b.imag == 0.0 && b.real == floor(b.real) && fabs(b.real) <= 100.0) {
         p = c_powi(a, (long)b.real);
+        _Py_ADJUST_ERANGE2(p.real, p.imag);
     }
     else {
         p = _Py_c_pow(a, b);
     }
 
-    _Py_ADJUST_ERANGE2(p.real, p.imag);
     if (errno == EDOM) {
         PyErr_SetString(PyExc_ZeroDivisionError,
                         "zero to a negative or complex power");

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	+Set :data:`errno` in :c:func:`_Py_c_pow` on overflows. Patch by Sergey B
	`2`	`+Kirpichev.`
Original file line number	Diff line number	Diff line change
`@@ -173,6 +173,8 @@ _Py_c_pow(Py_complex a, Py_complex b)`
`173`	`173`	`}`
`174`	`174`	`r.real = len*cos(phase);`
`175`	`175`	`r.imag = len*sin(phase);`
	`176`	`+`
	`177`	`+ _Py_ADJUST_ERANGE2(r.real, r.imag);`
`176`	`178`	`}`
`177`	`179`	`return r;`
`178`	`180`	`}`
`@@ -567,12 +569,12 @@ complex_pow(PyObject v, PyObject w, PyObject *z)`
`567`	`569`	`// a faster and more accurate algorithm.`
`568`	`570`	`if (b.imag == 0.0 && b.real == floor(b.real) && fabs(b.real) <= 100.0) {`
`569`	`571`	`p = c_powi(a, (long)b.real);`
	`572`	`+ _Py_ADJUST_ERANGE2(p.real, p.imag);`
`570`	`573`	`}`
`571`	`574`	`else {`
`572`	`575`	`p = _Py_c_pow(a, b);`
`573`	`576`	`}`
`574`	`577`
`575`		`- _Py_ADJUST_ERANGE2(p.real, p.imag);`
`576`	`578`	`if (errno == EDOM) {`
`577`	`579`	`PyErr_SetString(PyExc_ZeroDivisionError,`
`578`	`580`	`"zero to a negative or complex power");`