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Merge pull request #270 from boostorg/266

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Fix fixed precision case where we are short zero to the right of the decimal point
This commit is contained in:
Matt Borland
2025-06-16 17:14:24 -04:00
committed by GitHub
parent 3bf1d2268e 4d9d950178
commit 993c2fc349
3 changed files with 48 additions and 1 deletions
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13
include/boost/charconv/detail/dragonbox/floff.hpp
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@@ -1333,6 +1333,7 @@ BOOST_CHARCONV_SAFEBUFFERS to_chars_result floff(const double x, int precision,
auto buffer_size = static_cast<std::size_t>(last - first);
auto buffer = first;
bool trailing_zeros_removed = false;
BOOST_CHARCONV_ASSERT(precision >= 0);
using namespace detail;
@@ -3849,6 +3850,7 @@ insert_decimal_dot:
}
// Remove trailing zeros.
trailing_zeros_removed = true;
while (true)
{
auto prev = buffer - 1;
@@ -3903,7 +3905,16 @@ insert_decimal_dot:
print_2_digits(static_cast<std::uint32_t>(decimal_exponent_normalized), buffer);
buffer += 2;
}
}
}
else if (!trailing_zeros_removed && buffer - (decimal_dot_pos + 1) < precision)
{
// If we have fixed precision, and we don't have enough digits after the decimal yet
// insert a sufficient amount of zeros
const auto remaining_zeros = precision - (buffer - (decimal_dot_pos + 1));
BOOST_CHARCONV_ASSERT(remaining_zeros > 0);
std::memset(buffer, '0', static_cast<std::size_t>(remaining_zeros));
buffer += remaining_zeros;
}
return {buffer, std::errc()};

1
test/Jamfile
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@@ -70,4 +70,5 @@ run github_issue_166.cpp ;
run github_issue_166_float128.cpp ;
run github_issue_186.cpp ;
run github_issue_212.cpp ;
run github_issue_266.cpp ;
run github_issue_267.cpp ;

35
test/github_issue_266.cpp Normal file
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@@ -0,0 +1,35 @@
// Copyright 2025 Matt Borland
// Distributed under the Boost Software License, Version 1.0.
// https://www.boost.org/LICENSE_1_0.txt
//
// See: https://github.com/boostorg/charconv/issues/266
#include <boost/charconv.hpp>
#include <boost/core/lightweight_test.hpp>
template <typename T>
void test(T value, int precision, const char* correct_result)
{
char buffer[64] {};
const auto r = boost::charconv::to_chars(buffer, buffer + sizeof(buffer), value, boost::charconv::chars_format::fixed, precision);
BOOST_TEST_CSTR_EQ(buffer, correct_result);
BOOST_TEST(r);
}
int main()
{
test(123456789012345.6789012345678901, 5, "123456789012345.67188");
test(1234567890123456.789012345678901, 5, "1234567890123456.75000");
test(12345678901234567.89012345678901, 5, "12345678901234568.00000");
test(123456789012345678.9012345678901, 5, "123456789012345680.00000");
test(1234567890123456789.012345678901, 5, "1234567890123456768.00000");
test(123456789012345678901234567.8901, 5, "123456789012345678152597504.00000");
test(12345678901234567890123456.78901, 5, "12345678901234568244756480.00000");
test(1234567890123456789012345.678901, 5, "1234567890123456824475648.00000");
test(123456789012345678901234.5678901, 5, "123456789012345685803008.00000");
test(12345678901234567890123.45678901, 5, "12345678901234567741440.00000");
test(123456789012345678901.2345678901, 5, "123456789012345683968.00000");
return boost::report_errors();
}