libstdc++-v3/testsuite/20_util/to_chars/long_double.cc

   1 // Copyright (C) 2020-2022 Free Software Foundation, Inc.
   2 //
   3 // This file is part of the GNU ISO C++ Library.  This library is free
   4 // software; you can redistribute it and/or modify it under the
   5 // terms of the GNU General Public License as published by the
   6 // Free Software Foundation; either version 3, or (at your option)
   7 // any later version.
   8
   9 // This library is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13
  14 // You should have received a copy of the GNU General Public License along
  15 // with this library; see the file COPYING3.  If not see
  16 // <http://www.gnu.org/licenses/>.
  17
  18 // <charconv> is supported in C++14 as a GNU extension, but this test uses C++17
  19 // hexadecimal floating-point literals.
  20
  21 // When long double is larger than double, the long double to_chars overloads
  22 // are partially implemented in terms of printf, so this test in turn uses
  23 // printf to verify correctness these overloads.
  24 // When long double == double, the long double to_chars overloads are simple
  25 // wrappers around the corresponding double overloads.  Since they don't go
  26 // through printf, we can't portably verify their output by comparing it with
  27 // that of printf, so it's simplest to just not run this test on such targets;
  28 // correctness of these overloads is already implied by that of the double
  29 // overloads.
  30 // { dg-do run { target { c++17 && large_long_double } } }
  31 // { dg-do compile { target { c++17 && { ! large_long_double } } } }
  32
  33 // The system printf on these targets appear to be buggy.  FIXME: Make this test
  34 // more portable and robust to differences in system printf behavior.
  35 // { dg-xfail-run-if "Non-conforming printf (see PR98384)" { *-*-solaris* *-*-darwin* } }
  36
  37 // { dg-require-effective-target ieee_floats }
  38 // { dg-require-effective-target size32plus }
  39
  40 #include <charconv>
  41
  42 #include <cmath>
  43 #include <cstring>
  44 #include <iterator>
  45 #include <optional>
  46 #include <limits>
  47
  48 #include <testsuite_hooks.h>
  49
  50 using namespace std;
  51
  52 namespace detail
  53 {
  54   long double
  55   nextupl(long double x)
  56   { return nexttowardl(x, numeric_limits<long double>::infinity()); }
  57
  58   long double
  59   nextdownl(long double x)
  60   { return nexttowardl(x, -numeric_limits<long double>::infinity()); }
  61 }
  62
  63 // The long double overloads of std::to_chars currently just go through printf
  64 // (except for the hexadecimal formatting).
  65
  66 // Test our hand-written hexadecimal formatting implementation.
  67 void
  68 test01()
  69 {
  70   // Verifies correctness of the hexadecimal form [BEGIN,END) for VALUE by
  71   // round-tripping it through from_chars (if available).
  72   auto verify_via_from_chars = [] (char *begin, char *end, long double value) {
  73 #if __cpp_lib_to_chars >= 201611L
  74     long double roundtrip;
  75     auto result = from_chars(begin, end, roundtrip, chars_format::hex);
  76     VERIFY( result.ec == errc{} );
  77     VERIFY( result.ptr == end );
  78     VERIFY( roundtrip == value );
  79 #endif
  80   };
  81
  82   // Verifies correctness of the null-terminated hexadecimal form at BEGIN
  83   // for VALUE and PRECISION by comparing it with the output of printf's %La
  84   // conversion specifier.
  85   auto verify_via_printf = [] (char *begin, long double value,
  86                                optional<int> precision = nullopt) {
  87     char printf_buffer[1024] = {};
  88     if (precision.has_value())
  89       sprintf(printf_buffer, "%.*La", precision.value(), value);
  90     else
  91       sprintf(printf_buffer, "%La", value);
  92
  93     // Only compare with the output of printf if the leading hex digits agree.
  94     // If the leading hex digit of our form doesn't agree with that of printf,
  95     // then the two forms may still be equivalent (e.g. 1.1p+0 vs 8.8p-3).  But
  96     // if the leading hex digits do agree, then we do expect the two forms to be
  97     // the same.
  98     if (printf_buffer[strlen("0x")] == begin[0])
  99       VERIFY( !strcmp(begin, printf_buffer+strlen("0x")) );
 100   };
 101
 102   const long double hex_testcases[]
 103     = { detail::nextdownl(numeric_limits<long double>::max()),
 104         detail::nextupl(numeric_limits<long double>::min()),
 105         42.0L,
 106         0x1.2p+0L,
 107         0x1.23p+0L,
 108         0x1.234p+0L,
 109         0x1.2345p+0L,
 110         0x1.23456p+0L,
 111         0x1.234567p+0L,
 112         0x1.2345678p+0L,
 113         0x1.23456789p+0L,
 114         0x1.23456789p+0L,
 115         0x1.23456789ap+0L,
 116         0x1.23456789abp+0L,
 117         0x1.23456789abcp+0L,
 118         0x1.23456789abcdp+0L,
 119         0x1.23456789abcdep+0L,
 120         0x1.23456789abcdefp+0L,
 121         0x1.23456789abcdef0p+0L,
 122         0x1.23456789abcdef01p+0L,
 123         0x1.23456789abcdef012p+0L,
 124         0x1.23456789abcdef0123p+0L,
 125         0x1.23456789abcdef01234p+0L,
 126         0x1.23456789abcdef012345p+0L,
 127         0x1.23456789abcdef0123456p+0L,
 128         0x1.23456789abcdef01234567p+0L,
 129         0x1.23456789abcdef012345678p+0L,
 130         0x1.23456789abcdef0123456789p+0L,
 131         0x1.23456789abcdef0123456789ap+0L,
 132         0x1.23456789abcdef0123456789abp+0L,
 133         0x1.23456789abcdef0123456789abcp+0L,
 134         0x1.23456789abcdef0123456789abcdp+0L,
 135     };
 136
 137   for (int exponent : {-11000, -3000, -300, -50, -7, 0, 7, 50, 300, 3000, 11000})
 138     for (long double testcase : hex_testcases)
 139       {
 140         testcase = ldexpl(testcase, exponent);
 141         if (testcase == 0.0L || isinf(testcase))
 142           continue;
 143
 144         char to_chars_buffer[1024] = {};
 145         auto result = to_chars(begin(to_chars_buffer), end(to_chars_buffer),
 146                                testcase, chars_format::hex);
 147         VERIFY( result.ec == errc{} );
 148         *result.ptr = '\0';
 149         verify_via_from_chars(begin(to_chars_buffer), result.ptr, testcase);
 150         verify_via_printf(to_chars_buffer, testcase);
 151
 152         // Verify the nearby values, and also check they have a different
 153         // shortest form.
 154         for (long double nearby
 155              : { detail::nextdownl(testcase), detail::nextupl(testcase) })
 156           {
 157             char nearby_buffer[1024] = {};
 158             result = to_chars(begin(nearby_buffer), end(nearby_buffer),
 159                               nearby, chars_format::hex);
 160             VERIFY( result.ec == errc{} );
 161             *result.ptr = '\0';
 162             VERIFY( strcmp(nearby_buffer, to_chars_buffer) != 0);
 163             verify_via_from_chars(begin(nearby_buffer), result.ptr, nearby);
 164             verify_via_printf(nearby_buffer, nearby);
 165           }
 166
 167         for (int precision = -1; precision < 50; precision++)
 168           {
 169             result = to_chars(begin(to_chars_buffer), end(to_chars_buffer),
 170                               testcase, chars_format::hex, precision);
 171             VERIFY( result.ec == errc{} );
 172             *result.ptr = '\0';
 173             verify_via_printf(to_chars_buffer, testcase, precision);
 174           }
 175       }
 176 }
 177
 178 // Test the rest of the formatting modes, which go through printf.
 179 void
 180 test02()
 181 {
 182   const long double growth_factor = 1.442695040888963407359924681001892137L;
 183   for (chars_format fmt : {chars_format::fixed, chars_format::scientific,
 184                            chars_format::general})
 185     for (long double __value = 1.0L, count = 0; !isinf(__value);
 186          ++count <= 100.0L ? __value *= growth_factor : __value *= __value)
 187       for (const long double value : {__value, 1.0L/__value})
 188         {
 189           for (const int precision : {-1, 0, 10, 100, 10000})
 190             {
 191               const char* const printf_specifier
 192                 = (fmt == chars_format::fixed ? "%.*Lf"
 193                    : fmt == chars_format::scientific ? "%.*Le"
 194                    : fmt == chars_format::general ? "%.*Lg"
 195                    : nullptr);
 196               unsigned output_length = snprintf(nullptr, 0, printf_specifier,
 197                                                 precision, value);
 198
 199               char printf_buffer[output_length+1];
 200               snprintf(printf_buffer, output_length+1, printf_specifier,
 201                        precision, value);
 202
 203               char to_chars_buffer[output_length];
 204               auto result = to_chars(to_chars_buffer,
 205                                      to_chars_buffer+output_length,
 206                                      value, fmt, precision);
 207               VERIFY( result.ec == errc{} );
 208               VERIFY( !memcmp(printf_buffer, to_chars_buffer, output_length) );
 209
 210               result = to_chars(to_chars_buffer,
 211                                 to_chars_buffer+output_length-1,
 212                                 value, fmt, precision);
 213               VERIFY( result.ec == errc::value_too_large );
 214             }
 215
 216           // Verify that the nearby values have a different shortest form.
 217           char to_chars_buffer[50000];
 218           auto result = to_chars(begin(to_chars_buffer), end(to_chars_buffer),
 219                                  value, fmt);
 220           VERIFY( result.ec == errc{} );
 221           *result.ptr = '\0';
 222           char nearby_buffer[50000];
 223             {
 224               const long double smaller = detail::nextdownl(value);
 225               result = to_chars(begin(nearby_buffer), end(nearby_buffer),
 226                                 smaller, fmt);
 227               VERIFY( result.ec == errc{} );
 228               *result.ptr = '\0';
 229               VERIFY( strcmp(to_chars_buffer, nearby_buffer) != 0 );
 230             }
 231
 232             {
 233               long double larger = detail::nextupl(value);
 234               result = to_chars(begin(nearby_buffer), end(nearby_buffer),
 235                                 larger, fmt);
 236               VERIFY( result.ec == errc{} );
 237               *result.ptr = '\0';
 238               VERIFY( strcmp(to_chars_buffer, nearby_buffer) != 0 );
 239             }
 240         }
 241 }
 242
 243 int
 244 main()
 245 {
 246   test01();
 247   test02();
 248 }