diff --git a/include/mimalloc/internal.h b/include/mimalloc/internal.h
index e3e702fb..2188ac1f 100644
--- a/include/mimalloc/internal.h
+++ b/include/mimalloc/internal.h
@@ -8,7 +8,6 @@ terms of the MIT license. A copy of the license can be found in the file
 #ifndef MI_INTERNAL_H
 #define MI_INTERNAL_H
 
-
 // --------------------------------------------------------------------------
 // This file contains the internal API's of mimalloc and various utility
 // functions and macros.
@@ -18,6 +17,17 @@ terms of the MIT license. A copy of the license can be found in the file
 #include "track.h"
 #include "bits.h"
 
+
+// --------------------------------------------------------------------------
+// Compiler defines
+// --------------------------------------------------------------------------
+
+#if (MI_DEBUG>0)
+#define mi_trace_message(...)  _mi_trace_message(__VA_ARGS__)
+#else
+#define mi_trace_message(...)
+#endif
+
 #define mi_decl_cache_align     mi_decl_align(64)
 
 #if defined(_MSC_VER)
@@ -26,26 +36,59 @@ terms of the MIT license. A copy of the license can be found in the file
 #define mi_decl_noinline        __declspec(noinline)
 #define mi_decl_thread          __declspec(thread)
 #define mi_decl_align(a)        __declspec(align(a))
+#define mi_decl_noreturn        __declspec(noreturn)
 #define mi_decl_weak
 #define mi_decl_hidden
+#define mi_decl_cold
 #elif (defined(__GNUC__) && (__GNUC__ >= 3)) || defined(__clang__) // includes clang and icc
 #define mi_decl_noinline        __attribute__((noinline))
 #define mi_decl_thread          __thread
 #define mi_decl_align(a)        __attribute__((aligned(a)))
+#define mi_decl_noreturn        __attribute__((noreturn))
 #define mi_decl_weak            __attribute__((weak))
 #define mi_decl_hidden          __attribute__((visibility("hidden")))
+#if (__GNUC__ >= 4) || defined(__clang__)
+#define mi_decl_cold            __attribute__((cold))
+#else
+#define mi_decl_cold
+#endif
 #elif __cplusplus >= 201103L    // c++11
 #define mi_decl_noinline
 #define mi_decl_thread          thread_local
-#define mi_decl_cache_align     alignas(MI_CACHE_LINE)
+#define mi_decl_align(a)        alignas(a)
+#define mi_decl_noreturn        [[noreturn]]
 #define mi_decl_weak
 #define mi_decl_hidden
+#define mi_decl_cold
 #else
 #define mi_decl_noinline
 #define mi_decl_thread          __thread        // hope for the best :-)
 #define mi_decl_align(a)
+#define mi_decl_noreturn        
 #define mi_decl_weak
 #define mi_decl_hidden
+#define mi_decl_cold
+#endif
+
+#if defined(__GNUC__) || defined(__clang__)
+#define mi_unlikely(x)     (__builtin_expect(!!(x),false))
+#define mi_likely(x)       (__builtin_expect(!!(x),true))
+#elif (defined(__cplusplus) && (__cplusplus >= 202002L)) || (defined(_MSVC_LANG) && _MSVC_LANG >= 202002L)
+#define mi_unlikely(x)     (x) [[unlikely]]
+#define mi_likely(x)       (x) [[likely]]
+#else
+#define mi_unlikely(x)     (x)
+#define mi_likely(x)       (x)
+#endif
+
+#ifndef __has_builtin
+#define __has_builtin(x)    0
+#endif
+
+#if defined(__cplusplus)
+#define mi_decl_externc     extern "C"
+#else
+#define mi_decl_externc
 #endif
 
 #if (defined(__GNUC__) && (__GNUC__ >= 7)) || defined(__clang__) // includes clang and icc
@@ -67,11 +110,10 @@ terms of the MIT license. A copy of the license can be found in the file
 #define __wasi__
 #endif
 
-#if (MI_DEBUG>0)
-#define mi_trace_message(...)  _mi_trace_message(__VA_ARGS__)
-#else
-#define mi_trace_message(...)
-#endif
+
+// --------------------------------------------------------------------------
+// Internal functions
+// --------------------------------------------------------------------------
 
 
 // "libc.c"
@@ -261,7 +303,6 @@ bool          _mi_page_is_valid(mi_page_t* page);
 #endif
 
 
-
 /* -----------------------------------------------------------
    Assertions
 ----------------------------------------------------------- */
@@ -344,6 +385,32 @@ typedef struct mi_option_desc_s {
   const char*       legacy_name; // potential legacy option name
 } mi_option_desc_t;
 
+// ------------------------------------------------------
+// Assertions
+// ------------------------------------------------------
+
+#if (MI_DEBUG)
+// use our own assertion to print without memory allocation
+mi_decl_noreturn mi_decl_cold void _mi_assert_fail(const char* assertion, const char* fname, unsigned int line, const char* func) mi_attr_noexcept;
+#define mi_assert(expr)     ((expr) ? (void)0 : _mi_assert_fail(#expr,__FILE__,__LINE__,__func__))
+#else
+#define mi_assert(x)
+#endif
+
+#if (MI_DEBUG>1)
+#define mi_assert_internal    mi_assert
+#else
+#define mi_assert_internal(x)
+#endif
+
+#if (MI_DEBUG>2)
+#define mi_assert_expensive   mi_assert
+#else
+#define mi_assert_expensive(x)
+#endif
+
+
+
 /* -----------------------------------------------------------
   Inlined definitions
 ----------------------------------------------------------- */
diff --git a/src/options.c b/src/options.c
index 78aaedc4..7fa90f83 100644
--- a/src/options.c
+++ b/src/options.c
@@ -546,7 +546,7 @@ void _mi_warning_message(const char* fmt, ...) {
 
 
 #if MI_DEBUG
-void _mi_assert_fail(const char* assertion, const char* fname, unsigned line, const char* func ) {
+mi_decl_noreturn mi_decl_cold void _mi_assert_fail(const char* assertion, const char* fname, unsigned line, const char* func ) mi_attr_noexcept {
   _mi_fprintf(NULL, NULL, "mimalloc: assertion failed: at \"%s\":%u, %s\n  assertion: \"%s\"\n", fname, line, (func==NULL?"":func), assertion);
   abort();
 }