Merge pull request #795 from cppalliance/develop

Merge to Master for 3.0.1

doc/decimal.adoc

@@ -18,6 +18,7 @@ https://www.boost.org/LICENSE_1_0.txt
 Matt Borland and Chris Kormanyos
 
 include::decimal/overview.adoc[]
+include::decimal/basics.adoc[]
 include::decimal/api_reference.adoc[]
 include::decimal/generic_decimal.adoc[]
 include::decimal/decimal32.adoc[]

doc/decimal/basics.adoc

@@ -0,0 +1,85 @@
+////
+Copyright 2025 Matt Borland
+Distributed under the Boost Software License, Version 1.0.
+https://www.boost.org/LICENSE_1_0.txt
+////
+
+[#basics]
+= Basic Usage
+:idprefix: basics_
+
+== Construction of Decimal Types
+
+Every decimal type can be constructed in a few ways:
+
+1) The parameters to the constructor are like so:
+
+[source, c++]
+----
+template <typename T, typename T2>
+constexpr decimal32(T coeff, T2 exp, bool sign = false) noexcept;
+----
+
+Where types `T` and `T2` are integral types (signed and unsigned are both allowed).
+Lastly the sign follows the convention of `signbit` where `false` is positive and `true` is negative.
+If both a negative coefficient and a sign are passed then the resulting decimal number will be negative.
+The final number constructed is in the form (sign || coeff < 0 ? -1 : 1) x abs(coeff) x 10^exp.
+
+[souce, c++]
+----
+boost::decimal::decimal32 a {1, 0};         // constructs 1
+boost::decimal::decimal32 b {-2, 0};        // constructs -2
+boost::decimal::decimal32 c {2, 0, true};   // Also constructs -2
+boost::decimal::decimal32 d {-2, 0, true};  // Also constructs -2
+boost::decimal::decimal32 e {5, 5};         // constructs 5x10^5
+boost::decimal::decimal32 f {1234, -3}      // constructs 1.234 or 1234x10^-3
+----
+
+2) A decimal number can be explicitly or implicitly constructed from an integer.
+For example:
+
+[source, c++]
+----
+boost::decimal::decimal64 g = 1;
+boost::decimal::decimal32 h {-4};
+----
+
+3) A decimal number can only be explicitly constructed from a floating point type.
+For example:
+
+[source, c++]
+----
+boost::decimal::decimal128 pi {3.14};
+----
+
+NOTE: Due to the differences in decimal and binary floating point numbers there may be a difference in the resulting representation in decimal format, and thus it is not recommended to construct from binary floating point numbers
+
+== Using the Library
+
+The entire library should be accessed using the convenience header `<boost/decimal.hpp>`.
+A short example of the basic usage:
+
+[source, c++]
+----
+#include <boost/decimal.hpp>
+#include <iostream>
+#include <iomanip>
+
+int main()
+{
+    using namespace boost::decimal;
+
+    // Outputs 0.30000000000000004
+    std::cout << std::setprecision(17) << 0.1 + 0.2 << std::endl;
+
+    // Construct the two decimal values
+    constexpr decimal64 a {1, -1}; // 1e-1 or 0.1
+    constexpr decimal64 b {2, -1}; // 2e-1 or 0.2
+
+    // Outputs 0.30000000000000000
+    std::cout << a + b << std::endl;
+
+    return 0;
+}
+
+----

doc/decimal/charconv.adoc

@@ -143,6 +143,8 @@ BOOST_DECIMAL_CONSTEXPR std::to_chars_result to_chars(char* first, char* last, D
 } //namespace boost
 ----
 
+All `to_chars` functions ignore the effects of cohorts, and instead output normalized values.
+
 NOTE: `BOOST_DECIMAL_CONSTEXPR` is defined if:
 
  - `_MSC_FULL_VER` >= 192528326

doc/decimal/cmath.adoc

@@ -413,7 +413,7 @@ constexpr int quantexp128(decimal128 x) noexcept;
 
 Effects: if x is finite, returns its quantum exponent.
 
-Otherwise, a domain error occurs and `INT_MIN` is returned.
+Otherwise, `INT_MIN` is returned.
 
 === quantized
 

doc/decimal/decimal128.adoc

@@ -28,6 +28,8 @@ The encoding of Decimal128 is in the <<conversions, BID format>>.
 namespace boost {
 namespace decimal {
 
+class decimal128 {
+
 // Paragraph numbers are from ISO/IEC DTR 24733
 
 // 3.2.4.1 construct/copy/destroy
@@ -85,6 +87,8 @@ explicit constexpr operator std::bfloat16_t() const noexcept;
 explicit constexpr operator decimal32() const noexcept;
 explicit constexpr operator decimal64() const noexcept;
 
+}; // class decimal128
+
 } //namespace decimal
 } //namespace boost
 

doc/decimal/decimal128_fast.adoc

@@ -28,6 +28,8 @@ As is often the case this trades space for time by having greater storage width
 namespace boost {
 namespace decimal {
 
+class decimal128_fast {
+
 // Paragraph numbers are from ISO/IEC DTR 24733
 
 // 3.2.4.1 construct/copy/destroy
@@ -85,6 +87,8 @@ explicit constexpr operator std::bfloat16_t() const noexcept;
 explicit constexpr operator decimal32() const noexcept;
 explicit constexpr operator decimal64() const noexcept;
 
+}; // class decimal128_fast
+
 } //namespace decimal
 } //namespace boost
 

doc/decimal/decimal32.adoc

@@ -28,6 +28,8 @@ The encoding of Decimal32 is in the <<conversions, BID format>>.
 namespace boost {
 namespace decimal {
 
+class decimal32 {
+
 // Paragraph numbers are from ISO/IEC DTR 24733
 
 // 3.2.2.1 construct/copy/destroy
@@ -85,6 +87,8 @@ explicit constexpr operator std::bfloat16_t() const noexcept;
 explicit constexpr operator decimal64() const noexcept;
 explicit constexpr operator decimal128() const noexcept;
 
+}; // class decimal32
+
 } //namespace decimal
 } //namespace boost
 

doc/decimal/decimal32_fast.adoc

@@ -28,6 +28,8 @@ As is often the case this trades space for time by having greater storage width
 namespace boost {
 namespace decimal {
 
+class decimal32_fast {
+
 // Paragraph numbers are from ISO/IEC DTR 24733
 
 // 3.2.2.1 construct/copy/destroy
@@ -85,6 +87,8 @@ explicit constexpr operator std::bfloat16_t() const noexcept;
 explicit constexpr operator decimal64() const noexcept;
 explicit constexpr operator decimal128() const noexcept;
 
+}; // class decimal32_fast
+
 } //namespace decimal
 } //namespace boost
 

doc/decimal/decimal64.adoc

@@ -28,6 +28,8 @@ The encoding of Decimal64 is in the <<conversions, BID format>>.
 namespace boost {
 namespace decimal {
 
+class decimal64 {
+
 // Paragraph numbers are from ISO/IEC DTR 24733
 
 // 3.2.3.1 construct/copy/destroy
@@ -85,6 +87,8 @@ explicit constexpr operator std::bfloat16_t() const noexcept;
 explicit constexpr operator decimal32() const noexcept;
 explicit constexpr operator decimal128() const noexcept;
 
+}; // class decimal64
+
 } //namespace decimal
 } //namespace boost
 

doc/decimal/decimal64_fast.adoc

@@ -28,6 +28,8 @@ As is often the case this trades space for time by having greater storage width
 namespace boost {
 namespace decimal {
 
+class decimal64_fast {
+
 // Paragraph numbers are from ISO/IEC DTR 24733
 
 // 3.2.3.1 construct/copy/destroy
@@ -85,6 +87,8 @@ explicit constexpr operator std::bfloat16_t() const noexcept;
 explicit constexpr operator decimal32() const noexcept;
 explicit constexpr operator decimal128() const noexcept;
 
+}; // class decimal64_fast
+
 } //namespace decimal
 } //namespace boost
 

doc/decimal/overview.adoc

@@ -40,34 +40,3 @@ as well as emulated PPC64LE and STM32 using QEMU with the following compilers:
 
 Tested on https://github.com/cppalliance/decimal/actions[Github Actions] and https://drone.cpp.al/cppalliance/decimal[Drone].
 Coverage can be found on https://app.codecov.io/gh/cppalliance/decimal[Codecov].
-
-== Basic Usage
-
-The entire library should be accessed using the convince header `<boost/decimal.hpp>`.
-A short example of the basic usage:
-
-[source, c++]
-----
-#include <boost/decimal.hpp>
-#include <iostream>
-#include <iomanip>
-
-int main()
-{
-    using namespace boost::decimal;
-
-    // Outputs 0.30000000000000004
-    std::cout << std::setprecision(17) << 0.1 + 0.2;
-
-    // Construct the two decimal values
-    constexpr decimal64 a {1, -1}; // 1e-1 or 0.1
-    constexpr decimal64 b {2, -1}; // 2e-1 or 0.2
-
-    // Outputs 0.30000000000000000
-    std::cout << a + b << std::endl;
-
-    return 0;
-}
-
-----
-

include/boost/decimal/charconv.hpp

@@ -542,16 +542,16 @@ BOOST_DECIMAL_CONSTEXPR auto to_chars_fixed_impl(char* first, char* last, const
         {
             append_trailing_zeros = true;
         }
+    }
 
-        // In general formatting we remove trailing 0s
-        if (fmt == chars_format::general)
-        {
-
-            const auto zeros_removal {remove_trailing_zeros(significand)};
-            significand = zeros_removal.trimmed_number;
-            exponent += static_cast<int>(zeros_removal.number_of_removed_zeros);
-            num_dig -= static_cast<int>(zeros_removal.number_of_removed_zeros);
-        }
+    // In general formatting we remove trailing 0s
+    // Same with unspecified precision fixed formatting
+    if ((precision == -1 && fmt == chars_format::fixed) || fmt == chars_format::general)
+    {
+        const auto zeros_removal {remove_trailing_zeros(significand)};
+        significand = zeros_removal.trimmed_number;
+        exponent += static_cast<int>(zeros_removal.number_of_removed_zeros);
+        num_dig -= static_cast<int>(zeros_removal.number_of_removed_zeros);
     }
 
     // Make sure the result will fit in the buffer
@@ -569,25 +569,32 @@ BOOST_DECIMAL_CONSTEXPR auto to_chars_fixed_impl(char* first, char* last, const
             *first++ = '0';
             return {first, std::errc()};
         }
-        else if (num_leading_zeros > precision)
+        else if (precision != -1 && num_leading_zeros > precision)
         {
             *first++ = '0';
             *first++ = '.';
-            std::memset(first, '0', static_cast<std::size_t>(precision));
+            boost::decimal::detail::memset(first, '0', static_cast<std::size_t>(precision));
             return {first + precision, std::errc()};
         }
         else
         {
             *first++ = '0';
             *first++ = '.';
-            std::memset(first, '0', static_cast<std::size_t>(num_leading_zeros));
+            boost::decimal::detail::memset(first, '0', static_cast<std::size_t>(num_leading_zeros));
             first += num_leading_zeros;
 
             // We can skip the rest if there's nothing more to do for the required precision
             if (significand == 0)
             {
-                std::memset(first, '0', static_cast<std::size_t>(precision - num_leading_zeros));
-                return {first + precision, std::errc()};
+                if (precision - num_leading_zeros > 0)
+                {
+                    boost::decimal::detail::memset(first, '0', static_cast<std::size_t>(precision - num_leading_zeros));
+                    return {first + precision, std::errc()};
+                }
+                else
+                {
+                    return {first, std::errc()};
+                }
             }
         }
     }

include/boost/decimal/detail/memcpy.hpp

@@ -23,6 +23,7 @@
 #if defined(__GNUC__) && __GNUC__ >= 10
 #  pragma GCC diagnostic push
 #  pragma GCC diagnostic ignored "-Wstringop-overflow"
+#  pragma GCC diagnostic ignored "-Warray-bounds"
 #  define BOOST_DECIMAL_STRINGOP_OVERFLOW_DISABLED
 #endif
 

test/Jamfile

@@ -45,6 +45,7 @@ project : requirements
 run-fail benchmarks.cpp ;
 run compare_dec128_and_fast.cpp ;
 compile-fail concepts_test.cpp ;
+run crash_report_1.cpp ;
 run github_issue_426.cpp ;
 run github_issue_448.cpp ;
 run-fail github_issue_519.cpp ;

test/crash_report_1.cpp

@@ -0,0 +1,27 @@
+// Copyright 2025 Matt Borland
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/decimal.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <iostream>
+
+using namespace boost::decimal;
+
+int main()
+{
+    char buffer[64]{};
+    const auto print_val {0.000001_df};
+
+    const auto r = boost::decimal::to_chars(
+            buffer,
+            buffer + sizeof(buffer),
+            print_val,
+            boost::decimal::chars_format::fixed
+    );
+    *r.ptr = '\0';
+
+    BOOST_TEST_CSTR_EQ(buffer, "0.000001");
+
+    return boost::report_errors();
+}