gh-122681: remove m_atan2()/c_atan2() helpers (#122715)

Modules/_math.h

@@ -23,42 +23,3 @@ _Py_log1p(double x)
 }
 
 #define m_log1p _Py_log1p
-
-/*
-   wrapper for atan2 that deals directly with special cases before
-   delegating to the platform libm for the remaining cases.  This
-   is necessary to get consistent behaviour across platforms.
-   Windows, FreeBSD and alpha Tru64 are amongst platforms that don't
-   always follow C99.  Windows screws up atan2 for inf and nan, and
-   alpha Tru64 5.1 doesn't follow C99 for atan2(0., 0.).
-*/
-
-static double
-_Py_atan2(double y, double x)
-{
-    if (isnan(x) || isnan(y))
-        return Py_NAN;
-    if (isinf(y)) {
-        if (isinf(x)) {
-            if (copysign(1., x) == 1.)
-                /* atan2(+-inf, +inf) == +-pi/4 */
-                return copysign(0.25*Py_MATH_PI, y);
-            else
-                /* atan2(+-inf, -inf) == +-pi*3/4 */
-                return copysign(0.75*Py_MATH_PI, y);
-        }
-        /* atan2(+-inf, x) == +-pi/2 for finite x */
-        return copysign(0.5*Py_MATH_PI, y);
-    }
-    if (isinf(x) || y == 0.) {
-        if (copysign(1., x) == 1.)
-            /* atan2(+-y, +inf) = atan2(+-0, +x) = +-0. */
-            return copysign(0., y);
-        else
-            /* atan2(+-y, -inf) = atan2(+-0., -x) = +-pi. */
-            return copysign(Py_MATH_PI, y);
-    }
-    return atan2(y, x);
-}
-
-#define m_atan2 _Py_atan2

Modules/cmathmodule.c

@@ -925,7 +925,7 @@ cmath_phase_impl(PyObject *module, Py_complex z)
     double phi;
 
     errno = 0;
-    phi = m_atan2(z.imag, z.real); /* should not cause any exception */
+    phi = atan2(z.imag, z.real); /* should not cause any exception */
     if (errno != 0)
         return math_error();
     else
@@ -950,7 +950,7 @@ cmath_polar_impl(PyObject *module, Py_complex z)
     double r, phi;
 
     errno = 0;
-    phi = m_atan2(z.imag, z.real); /* should not cause any exception */
+    phi = atan2(z.imag, z.real); /* should not cause any exception */
     r = _Py_c_abs(z); /* sets errno to ERANGE on overflow */
     if (errno != 0)
         return math_error();

Modules/mathmodule.c

@@ -1066,7 +1066,7 @@ FUNC1(atan, atan, 0,
       "atan($module, x, /)\n--\n\n"
       "Return the arc tangent (measured in radians) of x.\n\n"
       "The result is between -pi/2 and pi/2.")
-FUNC2(atan2, m_atan2,
+FUNC2(atan2, atan2,
       "atan2($module, y, x, /)\n--\n\n"
       "Return the arc tangent (measured in radians) of y/x.\n\n"
       "Unlike atan(y/x), the signs of both x and y are considered.")