Try runs with older compilers

.github/workflows/ci.yml

@@ -38,8 +38,8 @@ jobs:
     uses: boostorg/boost-ci/.github/workflows/reusable.yml@master
     with:
       exclude_compiler: 'clang-3.5,clang-3.6,clang-3.7,clang-3.8,clang-3.9,clang-4.0,clang-5.0,clang-6.0,clang-7,
-                         clang-8,clang-9,clang-10,clang-11,clang-12,clang-13,clang-14,clang-15,clang-16,
-                         gcc-4.7,gcc-4.8,gcc-4.9,gcc-5,gcc-6,gcc-7,gcc-8,gcc-9,gcc-10,gcc-11,gcc-12'
+                         clang-8,clang-9,clang-10,
+                         gcc-4.7,gcc-4.8,gcc-4.9,gcc-5,gcc-6,gcc-7,gcc-8'
     # Example of customization:
     # with:
     #   enable_reflection: true

README.md

@@ -6,7 +6,7 @@ A safe and fully featured replacement for C++ builtin numeric types.
 
 This library requires C++20 and is tested on the following platforms:
 
-* GCC 13 and later
-* Clang 17 and later
+* GCC 9 and later
+* Clang 11 and later
 * Visual Studio 2022 and later
 * Intel OneAPI DPC++

doc/modules/ROOT/pages/overview.adoc

@@ -30,8 +30,8 @@ Safety critical applications
 Boost.safe_numbers is tested natively on Ubuntu (x86_64, x86_32, s390x, aarch64, ARM32v7), macOS (x86_64, and Apple Silicon), and Windows (x86_64, x86_32, and ARM64);
 as well as emulated PPC64LE using QEMU with the following compilers:
 
-* GCC 13 and later
-* Clang 17 and later
+* GCC 9 and later
+* Clang 11 and later
 * Visual Studio 2022 (14.3) and later
 * Intel OneAPI DPC++ 2024.2 and later
 

include/boost/safe_numbers/detail/config.hpp

@@ -56,4 +56,15 @@
 #  define BOOST_SAFE_NUMBERS_UNREACHABLE std::abort()
 #endif
 
+namespace boost::safe_numbers::detail {
+
+// Workaround for static_assert(false, ...) in if constexpr branches.
+// Before C++23 (P2593R1), static_assert(false) is ill-formed even in
+// discarded branches. Making the condition depend on a template parameter
+// defers evaluation until instantiation.
+template <typename...>
+inline constexpr auto dependent_false {false};
+
+} // namespace boost::safe_numbers::detail
+
 #endif // BOOST_SAFENUMBERS_CONFIG_HPP

include/boost/safe_numbers/detail/type_traits.hpp

@@ -53,7 +53,7 @@ struct underlying<unsigned_integer_basis<T>>
 } // namespace impl
 
 template <typename T>
-using underlying_type_t = impl::underlying<T>::type;
+using underlying_type_t = typename impl::underlying<T>::type;
 
 } // namespace boost::safe_numbers::detail
 

include/boost/safe_numbers/format.hpp

@@ -9,6 +9,8 @@
 #include <boost/safe_numbers/detail/int128/format.hpp>
 #include <boost/safe_numbers/detail/concepts.hpp>
 
+#ifdef BOOST_SAFE_NUMBERS_DETAIL_INT128_HAS_FORMAT
+
 #ifndef BOOST_SAFE_NUMBERS_BUILD_MODULE
 
 #include <format>
@@ -27,4 +29,6 @@ struct std::formatter<boost::safe_numbers::detail::unsigned_integer_basis<BasisT
     }
 };
 
+#endif // Has format
+
 #endif // BOOST_SAFE_NUMBERS_FORMAT_HPP

test/Jamfile

@@ -44,7 +44,7 @@ project : requirements
     <toolset>clang:<warnings-as-errors>on
     <toolset>gcc:<warnings-as-errors>on
 
-  [ requires cxx17_hdr_charconv cxx20_hdr_bit cxx20_hdr_compare cxx20_hdr_concepts cxx20_hdr_format ]
+  [ requires cxx20_hdr_bit cxx20_hdr_compare cxx20_hdr_concepts ]
   ;
 
 run quick.cpp ;

test/test_unsigned_std_format.cpp

@@ -9,10 +9,17 @@ import boost.safe_numbers;
 #else
 
 #include <boost/safe_numbers.hpp>
+
+#ifdef BOOST_SAFE_NUMBERS_DETAIL_INT128_HAS_FORMAT
+
 #include <format>
 
 #endif
 
+#endif
+
+#ifdef BOOST_SAFE_NUMBERS_DETAIL_INT128_HAS_FORMAT
+
 #include <boost/core/lightweight_test.hpp>
 
 using namespace boost::safe_numbers;
@@ -37,3 +44,12 @@ int main()
 
     return boost::report_errors();
 }
+
+#else
+
+int main()
+{
+    return 0;
+}
+
+#endif