Update single header

Author: tcbrindle

single_include/flux.hpp

@@ -91,10 +91,12 @@
 
 #define FLUX_DECLVAL(...)  ((static_cast<__VA_ARGS__(*)()noexcept>(nullptr))())
 
-#ifdef __GNUC__
-#define FLUX_ALWAYS_INLINE [[gnu::always_inline]]
+#if defined(__GNUC__)
+#  define FLUX_ALWAYS_INLINE [[gnu::always_inline]] inline
+#elif defined(_MSC_VER)
+#  define FLUX_ALWAYS_INLINE __forceinline
 #else
-#define FLUX_ALWAYS_INLINE
+#  define FLUX_ALWAYS_INLINE inline
 #endif
 
 #define FLUX_NO_UNIQUE_ADDRESS [[no_unique_address]]
@@ -124,7 +126,8 @@
 #include <type_traits>
 
 #define FLUX_ERROR_POLICY_TERMINATE 1
-#define FLUX_ERROR_POLICY_UNWIND     2
+#define FLUX_ERROR_POLICY_UNWIND    2
+#define FLUX_ERROR_POLICY_FAIL_FAST 3
 
 #define FLUX_OVERFLOW_POLICY_ERROR   10
 #define FLUX_OVERFLOW_POLICY_WRAP    11
@@ -158,6 +161,8 @@
 #  define FLUX_ERROR_POLICY FLUX_ERROR_POLICY_TERMINATE
 #elif defined(FLUX_UNWIND_ON_ERROR)
 #  define FLUX_ERROR_POLICY FLUX_ERROR_POLICY_UNWIND
+#elif defined(FLUX_FAIL_FAST_ON_ERROR)
+#  define FLUX_ERROR_POLICY FLUX_ERROR_POLICY_FAIL_FAST
 #else
 #  define FLUX_ERROR_POLICY FLUX_DEFAULT_ERROR_POLICY
 #endif // FLUX_TERMINATE_ON_ERROR
@@ -234,7 +239,8 @@ namespace flux {
 FLUX_EXPORT
 enum class error_policy {
     terminate = FLUX_ERROR_POLICY_TERMINATE,
-    unwind = FLUX_ERROR_POLICY_UNWIND
+    unwind = FLUX_ERROR_POLICY_UNWIND,
+    fail_fast = FLUX_ERROR_POLICY_FAIL_FAST
 };
 
 FLUX_EXPORT
@@ -294,6 +300,15 @@ inline constexpr bool enable_debug_asserts = FLUX_ENABLE_DEBUG_ASSERTS;
 #include <stdexcept>
 #include <type_traits>
 
+#if defined(__has_builtin)
+#  if __has_builtin(__builtin_trap)
+#    define FLUX_HAS_BUILTIN_TRAP 1
+#  endif
+#elif defined(_MSC_VER)
+#  include <intrin.h>
+#  define FLUX_HAS_FASTFAIL 1
+#endif
+
 namespace flux {
 
 FLUX_EXPORT
@@ -304,21 +319,51 @@ struct unrecoverable_error : std::logic_error {
 namespace detail {
 
 struct runtime_error_fn {
+private:
+    [[noreturn]]
+    FLUX_ALWAYS_INLINE
+    static void fail_fast()
+    {
+#if FLUX_HAS_BUILTIN_TRAP
+        __builtin_trap();
+#elif FLUX_HAS_FASTFAIL
+        __fastfail(7); // FAST_FAIL_FATAL_APP_EXIT
+#else
+        std::abort();
+#endif
+    }
+
     [[noreturn]]
+    static void unwind(const char* msg, std::source_location loc)
+    {
+        char buf[1024];
+        std::snprintf(buf, 1024, "%s:%u: Fatal error: %s",
+                      loc.file_name(), loc.line(), msg);
+        throw unrecoverable_error(buf);
+    }
+
+    [[noreturn]]
+    static void terminate(const char* msg, std::source_location loc)
+    {
+        if constexpr (config::print_error_on_terminate) {
+            std::fprintf(stderr, "%s:%u: Fatal error: %s\n",
+                         loc.file_name(), loc.line(), msg);
+        }
+        std::terminate();
+    }
+
+public:
+    [[noreturn]]
+    FLUX_ALWAYS_INLINE
     void operator()(char const* msg,
                     std::source_location loc = std::source_location::current()) const
     {
-        if constexpr (config::on_error == error_policy::unwind) {
-            char buf[1024];
-            std::snprintf(buf, 1024, "%s:%u: Fatal error: %s",
-                          loc.file_name(), loc.line(), msg);
-            throw unrecoverable_error(buf);
+        if constexpr (config::on_error == error_policy::fail_fast) {
+            fail_fast();
+        } else if constexpr (config::on_error == error_policy::unwind) {
+            unwind(msg, loc);
         } else {
-            if constexpr (config::print_error_on_terminate) {
-                std::fprintf(stderr, "%s:%u: Fatal error: %s\n",
-                             loc.file_name(), loc.line(), msg);
-            }
-            std::terminate();
+            terminate(msg, loc);
         }
     }
 };
@@ -368,8 +413,7 @@ struct indexed_bounds_check_fn {
                 }
             }
 #endif
-            assert_fn{}(idx >= T{0}, "index cannot be negative", loc);
-            assert_fn{}(idx < limit, "out-of-bounds sequence access", loc);
+            assert_fn{}(idx >= T{0} && idx < limit, "out-of-bounds sequence access", loc);
         }
     }
 };