libstdc++: Add floating-point std::to_chars implementation

[thirdparty/gcc.git] / libstdc++-v3 / testsuite / 20_util / to_chars / long_double.cc

// Copyright (C) 2020 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING3.  If not see
// <http://www.gnu.org/licenses/>.

// <charconv> is supported in C++14 as a GNU extension, but this test uses C++17
// hexadecimal floating-point literals.
// { dg-do run { target c++17 } }
// { dg-xfail-run-if "Ryu needs __int128" { large_long_double && { ! int128 } } }

#include <charconv>

#include <cmath>
#include <cstring>
#include <iterator>
#include <limits>

#include <testsuite_hooks.h>

using namespace std;

// The long double overloads of std::to_chars currently just go through printf
// (except for the hexadecimal formatting).

// Test our hand-written hexadecimal formatting implementation.
void
test01()
{
  const long double hex_testcases[]
    = { nextdownl(numeric_limits<long double>::max()),
	nextupl(numeric_limits<long double>::min()),
	42.0L,
	0x1.2p+0L,
	0x1.23p+0L,
	0x1.234p+0L,
	0x1.2345p+0L,
	0x1.23456p+0L,
	0x1.234567p+0L,
	0x1.2345678p+0L,
	0x1.23456789p+0L,
	0x1.23456789p+0L,
	0x1.23456789ap+0L,
	0x1.23456789abp+0L,
	0x1.23456789abcp+0L,
	0x1.23456789abcdp+0L,
	0x1.23456789abcdep+0L,
	0x1.23456789abcdefp+0L,
	0x1.23456789abcdef0p+0L,
	0x1.23456789abcdef01p+0L,
	0x1.23456789abcdef012p+0L,
	0x1.23456789abcdef0123p+0L,
	0x1.23456789abcdef01234p+0L,
	0x1.23456789abcdef012345p+0L,
	0x1.23456789abcdef0123456p+0L,
	0x1.23456789abcdef01234567p+0L,
	0x1.23456789abcdef012345678p+0L,
	0x1.23456789abcdef0123456789p+0L,
	0x1.23456789abcdef0123456789ap+0L,
	0x1.23456789abcdef0123456789abp+0L,
	0x1.23456789abcdef0123456789abcp+0L,
	0x1.23456789abcdef0123456789abcdp+0L,
    };

  for (int exponent : {-11000, -3000, -300, -50, -7, 0, 7, 50, 300, 3000, 11000})
    for (long double testcase : hex_testcases)
      {
	testcase = ldexpl(testcase, exponent);
	if (testcase == 0.0L || isinf(testcase))
	  continue;

	char to_chars_buffer[1024], printf_buffer[1024];
	memset(to_chars_buffer, '\0', sizeof(to_chars_buffer));
	memset(printf_buffer, '\0', sizeof(printf_buffer));

	auto result = to_chars(begin(to_chars_buffer), end(to_chars_buffer),
			       testcase, chars_format::hex);
	VERIFY( result.ec == errc{} );
	*result.ptr = '\0';
	sprintf(printf_buffer, "%La", testcase);
	VERIFY( !strcmp(to_chars_buffer, printf_buffer+strlen("0x")) );

	  {
	    // Verify that the nearby values have a different shortest form.
	    testcase = nextdownl(testcase);
	    result = to_chars(begin(to_chars_buffer), end(to_chars_buffer),
			      testcase, chars_format::hex);
	    VERIFY( result.ec == errc{} );
	    *result.ptr = '\0';
	    VERIFY( strcmp(to_chars_buffer, printf_buffer+strlen("0x")) != 0);
	    sprintf(printf_buffer, "%La", testcase);
	    VERIFY( !strcmp(to_chars_buffer, printf_buffer+strlen("0x")) );

	    testcase = nextupl(nextupl(testcase));
	    result = to_chars(begin(to_chars_buffer), end(to_chars_buffer),
			      testcase, chars_format::hex);
	    VERIFY( result.ec == errc{} );
	    *result.ptr = '\0';
	    VERIFY( strcmp(to_chars_buffer, printf_buffer+strlen("0x")) != 0);
	    sprintf(printf_buffer, "%La", testcase);
	    VERIFY( !strcmp(to_chars_buffer, printf_buffer+strlen("0x")) );

	    testcase = nextdownl(testcase);
	  }

	for (int precision = -1; precision < 50; precision++)
	  {
	    result = to_chars(begin(to_chars_buffer), end(to_chars_buffer),
			      testcase, chars_format::hex, precision);
	    VERIFY( result.ec == errc{} );
	    *result.ptr = '\0';
	    sprintf(printf_buffer, "%.*La", precision, testcase);
	    VERIFY( !strcmp(to_chars_buffer, printf_buffer+strlen("0x")) );
	  }
      }
}

// Test the rest of the formatting modes, which go through printf.
void
test02()
{
  const long double growth_factor = 1.442695040888963407359924681001892137L;
  for (chars_format fmt : {chars_format::fixed, chars_format::scientific,
			   chars_format::general})
    for (long double __value = 1.0L, count = 0; !isinf(__value);
	 ++count <= 100.0L ? __value *= growth_factor : __value *= __value)
      for (const long double value : {__value, 1.0L/__value})
	{
	  for (const int precision : {-1, 0, 10, 100, 10000})
	    {
	      const char* const printf_specifier
		= (fmt == chars_format::fixed ? "%.*Lf"
		   : fmt == chars_format::scientific ? "%.*Le"
		   : fmt == chars_format::general ? "%.*Lg"
		   : nullptr);
	      unsigned output_length = snprintf(nullptr, 0, printf_specifier,
						precision, value);

	      char printf_buffer[output_length+1];
	      snprintf(printf_buffer, output_length+1, printf_specifier,
		       precision, value);

	      char to_chars_buffer[output_length];
	      auto result = to_chars(to_chars_buffer,
				     to_chars_buffer+output_length,
				     value, fmt, precision);
	      VERIFY( result.ec == errc{} );
	      VERIFY( !memcmp(printf_buffer, to_chars_buffer, output_length) );

	      result = to_chars(to_chars_buffer,
				to_chars_buffer+output_length-1,
				value, fmt, precision);
	      VERIFY( result.ec == errc::value_too_large );
	    }

	  // Verify that the nearby values have a different shortest form.
	  char to_chars_buffer[50000];
	  auto result = to_chars(begin(to_chars_buffer), end(to_chars_buffer),
				 value, fmt);
	  VERIFY( result.ec == errc{} );
	  *result.ptr = '\0';
	  char nearby_buffer[50000];
	    {
	      const long double smaller = nextdownl(value);
	      result = to_chars(begin(nearby_buffer), end(nearby_buffer),
				smaller, fmt);
	      VERIFY( result.ec == errc{} );
	      *result.ptr = '\0';
	      VERIFY( strcmp(to_chars_buffer, nearby_buffer) != 0 );
	    }

	    {
	      long double larger = nextupl(value);
	      result = to_chars(begin(nearby_buffer), end(nearby_buffer),
				larger, fmt);
	      VERIFY( result.ec == errc{} );
	      *result.ptr = '\0';
	      VERIFY( strcmp(to_chars_buffer, nearby_buffer) != 0 );
	    }
	}
}

int
main()
{
  test01();
  test02();
}