Add user and automatic configuration macro to disable exceptions

.github/workflows/ci.yml

@@ -119,6 +119,14 @@ jobs:
             container: ubuntu:24.04
             install:
               - g++-14-multilib
+          - toolset: gcc-14
+            cxxstd: "03,11,14,17,20,23,2c"
+            cxxflags: -fno-exceptions
+            address_model: "64"
+            os: ubuntu-latest
+            container: ubuntu:24.04
+            install:
+              - g++-14-multilib
           - toolset: gcc-14
             cxxstd: "03,11,14,17,20,23,2c"
             address_model: "32"

doc/modules/ROOT/nav.adoc

@@ -45,6 +45,8 @@
 * xref:functional.adoc[]
 * xref:limits.adoc[]
 * xref:config.adoc[]
+** xref:config.adoc#configuration_user[User Configuration]
+** xref:config.adoc#configuration_automatic[Automatic Configuration]
 * xref:benchmarks.adoc[]
 ** xref:benchmarks.adoc#x64_linux_benchmarks[x64 Linux]
 ** xref:benchmarks.adoc#x64_windows_benchmarks[x64 Windows]

doc/modules/ROOT/pages/api_reference.adoc

@@ -46,4 +46,20 @@ enums, constants and macros that are provided in this library.
 [#api_ref_macros]
 == Macros
 
-See: xref:config.adoc[configuration]
+=== User Configuration
+
+- xref:config.adoc#configuration_user[`BOOST_DECIMAL_DISABLE_CASSERT`]
+- xref:config.adoc#configuration_user[`BOOST_DECIMAL_DISABLE_IOSTREAM`]
+- xref:config.adoc#configuration_user[`BOOST_DECIMAL_DISABLE_CLIB`]
+- xref:config.adoc#configuration_user[`BOOST_DECIMAL_DISABLE_EXCEPTIONS`]
+- xref:config.adoc#configuration_user[`BOOST_DECIMAL_ALLOW_IMPLICIT_CONVERSIONS`]
+- xref:config.adoc#configuration_user[`BOOST_DECIMAL_FAST_MATH`]
+- xref:config.adoc#configuration_user[`BOOST_DECIMAL_DEC_EVAL_METHOD`]
+
+=== Automatic Configuration
+
+- xref:config.adoc#configuration_automatic[`BOOST_DECIMAL_CXX20_CONSTEXPR`]
+- xref:config.adoc#configuration_automatic[`BOOST_DECIMAL_CONSTEXPR`]
+- xref:config.adoc#configuration_automatic[`BOOST_DECIMAL_HAS_STD_CHARCONV`]
+- xref:config.adoc#configuration_automatic[`BOOST_DECIMAL_HAS_STD_STRING_VIEW`]
+

doc/modules/ROOT/pages/config.adoc

@@ -8,6 +8,7 @@ https://www.boost.org/LICENSE_1_0.txt
 = Configuration Macros
 :idprefix: config_
 
+[#configuration_user]
 == User Configurable Macros
 
 The following configuration macros are available:
@@ -18,6 +19,9 @@ The following configuration macros are available:
 
 - `BOOST_DECIMAL_DISABLE_CLIB`: Defines both of the above macros. In testing this reduces ROM usage by ~50% and can be useful if running on embedded platforms.
 
+- `BOOST_DECIMAL_DISABLE_EXCEPTIONS`: This allows the user to disable any calls to `throw`.
+This macro will also be set automatically in the presence of `-fno-exceptions` or various `/EH` flags on MSVC.
+
 - `BOOST_DECIMAL_ALLOW_IMPLICIT_CONVERSIONS`: Allows a binary floating-point type (e.g. `double`) to be implicitly converted to a decimal floating point type.
 This option is not recommended, but can be useful if you want to use specific functionality from the standard library with internal conversions such as:
 
@@ -44,6 +48,7 @@ Again, it must be defined before inclusion of decimal headers like so:
 
 - `BOOST_DECIMAL_DEC_EVAL_METHOD`: See <cfloat> section for explanation
 
+[#configuration_automatic]
 == Automatic Configuration Macros
 
 - `BOOST_DECIMAL_CXX20_CONSTEXPR`: This is defined to `constexpr` when compiling with C++20 or greater, otherwise it expands to nothing.

include/boost/decimal/detail/config.hpp

@@ -354,4 +354,32 @@ typedef unsigned __int128 builtin_uint128_t;
 #  endif
 #endif
 
+// Detect if we can throw or not
+// First check if the user said no explicitly
+// Then check if it's been disabled elsewhere
+
+#ifdef BOOST_DECIMAL_DISABLE_EXCEPTIONS
+
+#  define BOOST_DECIMAL_THROW_EXCEPTION(expr)
+
+#else
+
+#  ifdef _MSC_VER
+#    ifdef _CPPUNWIND
+#      define BOOST_DECIMAL_THROW_EXCEPTION(expr) throw expr;
+#    else
+#      define BOOST_DECIMAL_THROW_EXCEPTION(expr)
+#      define BOOST_DECIMAL_DISABLE_EXCEPTIONS
+#    endif
+#  else
+#    ifdef __EXCEPTIONS
+#      define BOOST_DECIMAL_THROW_EXCEPTION(expr) throw expr;
+#    else
+#      define BOOST_DECIMAL_THROW_EXCEPTION(expr)
+#      define BOOST_DECIMAL_DISABLE_EXCEPTIONS
+#    endif
+#endif
+
+#endif // Exceptions
+
 #endif // BOOST_DECIMAL_DETAIL_CONFIG_HPP

include/boost/decimal/fmt_format.hpp

@@ -11,6 +11,7 @@
 
 #include <fmt/format.h>
 #include <fmt/base.h>
+#include <boost/decimal/detail/config.hpp>
 #include <boost/decimal/charconv.hpp>
 #include <algorithm>
 #include <format>
@@ -93,10 +94,10 @@ constexpr auto parse_impl(ParseContext &ctx)
             case 'a':
                 fmt = chars_format::hex;
                 break;
-                // LCOV_EXCL_START
+            // LCOV_EXCL_START
             default:
-                throw std::logic_error("Invalid format specifier");
-                // LCOV_EXCL_STOP
+                BOOST_DECIMAL_THROW_EXCEPTION(std::logic_error("Invalid format specifier"));
+            // LCOV_EXCL_STOP
         }
     }
 

include/boost/decimal/format.hpp

@@ -5,12 +5,13 @@
 #ifndef BOOST_DECIMAL_FORMAT_HPP
 #define BOOST_DECIMAL_FORMAT_HPP
 
-// Many compilers seem to have <format> with completly broken support so narrow down our support range
+// Many compilers seem to have <format> with completely broken support so narrow down our support range
 #if (__cplusplus >= 202002L || (defined(_MSVC_LANG) && _MSVC_LANG >= 202002L)) && !defined(BOOST_DECIMAL_DISABLE_CLIB) && \
     ((defined(__GNUC__) && __GNUC__ >= 13) || (defined(__clang__) && __clang_major__ >= 18) || (defined(_MSC_VER) && _MSC_VER >= 1940))
 
 #define BOOST_DECIMAL_HAS_FORMAT_SUPPORT
 
+#include <boost/decimal/detail/config.hpp>
 #include <boost/decimal/charconv.hpp>
 #include <algorithm>
 #include <format>
@@ -91,7 +92,7 @@ constexpr auto parse_impl(ParseContext &ctx)
                 break;
             // LCOV_EXCL_START
             default:
-                throw std::format_error("Invalid format specifier");
+                BOOST_DECIMAL_THROW_EXCEPTION(std::format_error("Invalid format specifier"));
             // LCOV_EXCL_STOP
         }
     }

test/test_big_uints.cpp

@@ -2,7 +2,9 @@
 // Distributed under the Boost Software License, Version 1.0.
 // https://www.boost.org/LICENSE_1_0.txt
 
-#if defined(__MINGW32__)
+#include <boost/decimal.hpp>
+
+#if defined(__MINGW32__) || defined(BOOST_DECIMAL_DISABLE_EXCEPTIONS)
 
 // TODO(ckormanyos) disable -Werror in BJAM specifically for this file, as it gets
 // a hard-coded, non-removable warning (-Werror) propagated up from Multiprecision.
@@ -20,7 +22,6 @@ int main()
 // Propagates up from boost.math
 #define _SILENCE_CXX23_DENORM_DEPRECATION_WARNING
 
-#include <boost/decimal.hpp>
 #include <boost/decimal/detail/u256.hpp>
 
 #if defined(__clang__)

test/test_decimal32_fast_stream.cpp

@@ -111,6 +111,8 @@ void test_ostream()
     BOOST_TEST_CSTR_EQ(neg_snan.str().c_str(), "-nan(snan)");
 }
 
+#ifndef BOOST_DECIMAL_DISABLE_EXCEPTIONS
+
 void test_locales()
 {
     const char buffer[] = "1,1897e+02";
@@ -142,13 +144,15 @@ void test_locales()
     BOOST_TEST_CSTR_EQ(out.str().c_str(), buffer);
 }
 
+#endif
+
 int main()
 {
     test_istream();
     test_ostream();
 
     // Homebrew GCC does not support locales
-    #if !(defined(__GNUC__) && __GNUC__ >= 5 && defined(__APPLE__)) && !defined(BOOST_DECIMAL_QEMU_TEST)
+    #if !(defined(__GNUC__) && __GNUC__ >= 5 && defined(__APPLE__)) && !defined(BOOST_DECIMAL_QEMU_TEST) && !defined(BOOST_DECIMAL_DISABLE_EXCEPTIONS)
     test_locales();
     #endif
 

test/test_decimal32_stream.cpp

@@ -111,6 +111,8 @@ void test_ostream()
     BOOST_TEST_CSTR_EQ(neg_snan.str().c_str(), "-nan(snan)");
 }
 
+#ifndef BOOST_DECIMAL_DISABLE_EXCEPTIONS
+
 void test_locales()
 {
     const char buffer[] = "1,1897e+02";
@@ -142,13 +144,15 @@ void test_locales()
     BOOST_TEST_CSTR_EQ(out.str().c_str(), buffer);
 }
 
+#endif
+
 int main()
 {
     test_istream();
     test_ostream();
 
     // Homebrew GCC does not support locales
-    #if !(defined(__GNUC__) && __GNUC__ >= 5 && defined(__APPLE__)) && !defined(BOOST_DECIMAL_QEMU_TEST)
+    #if !(defined(__GNUC__) && __GNUC__ >= 5 && defined(__APPLE__)) && !defined(BOOST_DECIMAL_QEMU_TEST) && !defined(BOOST_DECIMAL_DISABLE_EXCEPTIONS)
     test_locales();
     #endif
 

test/test_snprintf.cpp

@@ -80,7 +80,7 @@ void test_uppercase(T value, const char* format_sprintf, chars_format fmt = char
     BOOST_TEST_EQ(num_bytes, r.ptr - charconv_buffer);
 }
 
-#if !(defined(__APPLE__) && defined(__GNUC__) && !defined(__clang__))
+#if !(defined(__APPLE__) && defined(__GNUC__) && !defined(__clang__)) && !defined(BOOST_DECIMAL_DISABLE_EXCEPTIONS)
 void test_locales()
 {
     const char buffer[] = "1,1897e+02";
@@ -227,7 +227,7 @@ int main()
     test_bootstrap<decimal128_t>();
 
     // Homebrew gcc on mac does not support locales
-    #if !(defined(__APPLE__) && defined(__GNUC__) && !defined(__clang__)) && !defined(BOOST_DECIMAL_QEMU_TEST)
+    #if !(defined(__APPLE__) && defined(__GNUC__) && !defined(__clang__)) && !defined(BOOST_DECIMAL_QEMU_TEST) && !defined(BOOST_DECIMAL_DISABLE_EXCEPTIONS)
     test_locales();
     #endif
 

test/test_strtod.cpp

@@ -137,6 +137,8 @@ void test_strtod_edges()
     BOOST_TEST(isnan(boost::decimal::strtod<T>(junk_str, nullptr))) && BOOST_TEST_EQ(errno, EINVAL);
 }
 
+#ifndef BOOST_DECIMAL_DISABLE_EXCEPTIONS
+
 template <typename T>
 void test_locales()
 {
@@ -164,6 +166,8 @@ void test_locales()
     BOOST_TEST_EQ(valdiation_value, val);
 }
 
+#endif
+
 template <typename T>
 void test_spot(const char* str, T val)
 {
@@ -278,7 +282,7 @@ int main()
     test_alloc<decimal64_t>();
 
     // Homebrew GCC does not support locales
-    #if !(defined(__GNUC__) && __GNUC__ >= 5 && defined(__APPLE__)) && !defined(BOOST_DECIMAL_QEMU_TEST)
+    #if !(defined(__GNUC__) && __GNUC__ >= 5 && defined(__APPLE__)) && !defined(BOOST_DECIMAL_QEMU_TEST) && !defined(BOOST_DECIMAL_DISABLE_EXCEPTIONS)
     test_locales<decimal32_t>();
     test_locales<decimal64_t>();
     test_locales<decimal128_t>();