libstdc++-v3/testsuite/special_functions/14_expint/pr68397.cc

   1 // { dg-do run { target c++11 } }
   2 // { dg-options "-D__STDCPP_WANT_MATH_SPEC_FUNCS__" }
   3 // Copyright (C) 2017-2025 Free Software Foundation, Inc.
   4 //
   5 // This file is part of the GNU ISO C++ Library.  This library is free
   6 // software; you can redistribute it and/or modify it under the
   7 // terms of the GNU General Public License as published by the
   8 // Free Software Foundation; either version 3, or (at your option)
   9 // any later version.
  10 //
  11 // This library is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15 //
  16 // You should have received a copy of the GNU General Public License along
  17 // with this library; see the file COPYING3.  If not see
  18 // <http://www.gnu.org/licenses/>.
  19
  20 // PR libstdc++/68397 -  std::tr1::expint fails in __expint_En_cont_frac
  21 // for some long double arguments due to low __max_iter value
  22
  23 #include <cmath>
  24 #include <testsuite_hooks.h>
  25
  26 void
  27 test01()
  28 {
  29   // Answers from Wolfram Alpha.
  30   long double ans_ok = -0.10001943365331651406888645149537315243646135979573L;
  31   long double ans_bomb = -0.10777727809650077516264612749163100483995270163783L;
  32
  33   auto Ei_ok = std::expint(-1.500001L);
  34   auto diff_ok = Ei_ok - ans_ok;
  35   VERIFY(std::abs(diff_ok) < 1.0e-15);
  36
  37   auto Ei_bomb = std::expint(-1.450001L);
  38   auto diff_bomb = Ei_bomb - ans_bomb;
  39   VERIFY(std::abs(diff_bomb) < 1.0e-15);
  40 }
  41
  42 int
  43 main()
  44 {
  45   test01();
  46   return 0;
  47 }