diff --git a/qjs.c b/qjs.c
index fe500d5..6cbbd6c 100644
--- a/qjs.c
+++ b/qjs.c
@@ -165,12 +165,6 @@ static JSContext *JS_NewCustomContext(JSRuntime *rt)
     return ctx;
 }
 
-#if defined(__APPLE__)
-#define MALLOC_OVERHEAD  0
-#else
-#define MALLOC_OVERHEAD  8
-#endif
-
 struct trace_malloc_data {
     uint8_t *base;
 };
@@ -188,7 +182,7 @@ __attribute__((format(gnu_printf, 2, 3)))
 #else
 __attribute__((format(printf, 2, 3)))
 #endif
-    js_trace_malloc_printf(JSMallocState *s, const char *fmt, ...)
+    js_trace_malloc_printf(void *opaque, const char *fmt, ...)
 {
     va_list ap;
     int c;
@@ -203,7 +197,7 @@ __attribute__((format(printf, 2, 3)))
                     printf("NULL");
                 } else {
                     printf("H%+06lld.%zd",
-                           js_trace_malloc_ptr_offset(ptr, s->opaque),
+                           js_trace_malloc_ptr_offset(ptr, opaque),
                            js__malloc_usable_size(ptr));
                 }
                 fmt++;
@@ -226,87 +220,36 @@ static void js_trace_malloc_init(struct trace_malloc_data *s)
     free(s->base = malloc(8));
 }
 
-static void *js_trace_calloc(JSMallocState *s, size_t count, size_t size)
+static void *js_trace_calloc(void *opaque, size_t count, size_t size)
 {
     void *ptr;
-
-    /* Do not allocate zero bytes: behavior is platform dependent */
-    assert(count != 0 && size != 0);
-
-    if (size > 0)
-        if (unlikely(count != (count * size) / size))
-            return NULL;
-
-    /* When malloc_limit is 0 (unlimited), malloc_limit - 1 will be SIZE_MAX. */
-    if (unlikely(s->malloc_size + (count * size) > s->malloc_limit - 1))
-        return NULL;
     ptr = calloc(count, size);
-    js_trace_malloc_printf(s, "C %zd %zd -> %p\n", count, size, ptr);
-    if (ptr) {
-        s->malloc_count++;
-        s->malloc_size += js__malloc_usable_size(ptr) + MALLOC_OVERHEAD;
-    }
+    js_trace_malloc_printf(opaque, "C %zd %zd -> %p\n", count, size, ptr);
     return ptr;
 }
 
-static void *js_trace_malloc(JSMallocState *s, size_t size)
+static void *js_trace_malloc(void *opaque, size_t size)
 {
+    (void) opaque;
     void *ptr;
-
-    /* Do not allocate zero bytes: behavior is platform dependent */
-    assert(size != 0);
-
-    /* When malloc_limit is 0 (unlimited), malloc_limit - 1 will be SIZE_MAX. */
-    if (unlikely(s->malloc_size + size > s->malloc_limit - 1))
-        return NULL;
     ptr = malloc(size);
-    js_trace_malloc_printf(s, "A %zd -> %p\n", size, ptr);
-    if (ptr) {
-        s->malloc_count++;
-        s->malloc_size += js__malloc_usable_size(ptr) + MALLOC_OVERHEAD;
-    }
+    js_trace_malloc_printf(opaque, "A %zd -> %p\n", size, ptr);
     return ptr;
 }
 
-static void js_trace_free(JSMallocState *s, void *ptr)
+static void js_trace_free(void *opaque, void *ptr)
 {
     if (!ptr)
         return;
-
-    js_trace_malloc_printf(s, "F %p\n", ptr);
-    s->malloc_count--;
-    s->malloc_size -= js__malloc_usable_size(ptr) + MALLOC_OVERHEAD;
+    js_trace_malloc_printf(opaque, "F %p\n", ptr);
     free(ptr);
 }
 
-static void *js_trace_realloc(JSMallocState *s, void *ptr, size_t size)
+static void *js_trace_realloc(void *opaque, void *ptr, size_t size)
 {
-    size_t old_size;
-
-    if (!ptr) {
-        if (size == 0)
-            return NULL;
-        return js_trace_malloc(s, size);
-    }
-
-    if (unlikely(size == 0)) {
-        js_trace_free(s, ptr);
-        return NULL;
-    }
-
-    old_size = js__malloc_usable_size(ptr);
-
-    /* When malloc_limit is 0 (unlimited), malloc_limit - 1 will be SIZE_MAX. */
-    if (s->malloc_size + size - old_size > s->malloc_limit - 1)
-        return NULL;
-
-    js_trace_malloc_printf(s, "R %zd %p", size, ptr);
-
+    js_trace_malloc_printf(opaque, "R %zd %p", size, ptr);
     ptr = realloc(ptr, size);
-    js_trace_malloc_printf(s, " -> %p\n", ptr);
-    if (ptr) {
-        s->malloc_size += js__malloc_usable_size(ptr) - old_size;
-    }
+    js_trace_malloc_printf(opaque, " -> %p\n", ptr);
     return ptr;
 }
 
diff --git a/quickjs.c b/quickjs.c
index ae87f22..c9ecba9 100644
--- a/quickjs.c
+++ b/quickjs.c
@@ -213,6 +213,13 @@ typedef enum {
     JS_GC_PHASE_REMOVE_CYCLES,
 } JSGCPhaseEnum;
 
+typedef struct JSMallocState {
+    size_t malloc_count;
+    size_t malloc_size;
+    size_t malloc_limit;
+    void *opaque; /* user opaque */
+} JSMallocState;
+
 struct JSRuntime {
     JSMallocFunctions mf;
     JSMallocState malloc_state;
@@ -1380,22 +1387,91 @@ static size_t js_malloc_usable_size_unknown(const void *ptr)
 
 void *js_calloc_rt(JSRuntime *rt, size_t count, size_t size)
 {
-    return rt->mf.js_calloc(&rt->malloc_state, count, size);
+    void *ptr;
+    JSMallocState *s;
+
+    /* Do not allocate zero bytes: behavior is platform dependent */
+    assert(count != 0 && size != 0);
+
+    if (size > 0)
+        if (unlikely(count != (count * size) / size))
+            return NULL;
+
+    s = &rt->malloc_state;
+    /* When malloc_limit is 0 (unlimited), malloc_limit - 1 will be SIZE_MAX. */
+    if (unlikely(s->malloc_size + (count * size) > s->malloc_limit - 1))
+        return NULL;
+
+    ptr = rt->mf.js_calloc(s->opaque, count, size);
+    if (!ptr)
+        return NULL;
+
+    s->malloc_count++;
+    s->malloc_size += js__malloc_usable_size(ptr) + MALLOC_OVERHEAD;
+    return ptr;
 }
 
 void *js_malloc_rt(JSRuntime *rt, size_t size)
 {
-    return rt->mf.js_malloc(&rt->malloc_state, size);
+    void *ptr;
+    JSMallocState *s;
+
+    /* Do not allocate zero bytes: behavior is platform dependent */
+    assert(size != 0);
+
+    s = &rt->malloc_state;
+    /* When malloc_limit is 0 (unlimited), malloc_limit - 1 will be SIZE_MAX. */
+    if (unlikely(s->malloc_size + size > s->malloc_limit - 1))
+        return NULL;
+
+    ptr = rt->mf.js_malloc(s->opaque, size);
+    if (!ptr)
+        return NULL;
+
+    s->malloc_count++;
+    s->malloc_size += js__malloc_usable_size(ptr) + MALLOC_OVERHEAD;
+    return ptr;
 }
 
 void js_free_rt(JSRuntime *rt, void *ptr)
 {
-    rt->mf.js_free(&rt->malloc_state, ptr);
+    JSMallocState *s;
+
+    if (!ptr)
+        return;
+
+    s = &rt->malloc_state;
+    s->malloc_count--;
+    s->malloc_size -= js__malloc_usable_size(ptr) + MALLOC_OVERHEAD;
+    rt->mf.js_free(s->opaque, ptr);
 }
 
 void *js_realloc_rt(JSRuntime *rt, void *ptr, size_t size)
 {
-    return rt->mf.js_realloc(&rt->malloc_state, ptr, size);
+    size_t old_size;
+    JSMallocState *s;
+
+    if (!ptr) {
+        if (size == 0)
+            return NULL;
+        return js_malloc_rt(rt, size);
+    }
+    if (unlikely(size == 0)) {
+        js_free_rt(rt, ptr);
+        return NULL;
+    }
+    old_size = js__malloc_usable_size(ptr);
+    s = &rt->malloc_state;
+    /* When malloc_limit is 0 (unlimited), malloc_limit - 1 will be SIZE_MAX. */
+    if (s->malloc_size + size - old_size > s->malloc_limit - 1)
+        return NULL;
+
+    ptr = rt->mf.js_realloc(s->opaque, ptr, size);
+    if (!ptr)
+        return NULL;
+
+    s->malloc_size += js__malloc_usable_size(ptr) - old_size;
+    return ptr;
 }
 
 static void *js_dbuf_realloc(void *opaque, void *ptr, size_t size)
@@ -1651,9 +1727,12 @@ JSRuntime *JS_NewRuntime2(const JSMallocFunctions *mf, void *opaque)
     ms.opaque = opaque;
     ms.malloc_limit = 0;
 
-    rt = mf->js_calloc(&ms, 1, sizeof(JSRuntime));
+    rt = mf->js_calloc(opaque, 1, sizeof(JSRuntime));
     if (!rt)
         return NULL;
+    /* Inline what js_malloc_rt does since we cannot use it here. */
+    ms.malloc_count++;
+    ms.malloc_size += js__malloc_usable_size(rt) + MALLOC_OVERHEAD;
     rt->mf = *mf;
     if (!rt->mf.js_malloc_usable_size) {
         /* use dummy function if none provided */
@@ -1718,84 +1797,24 @@ void JS_SetRuntimeOpaque(JSRuntime *rt, void *opaque)
     rt->user_opaque = opaque;
 }
 
-static void *js_def_calloc(JSMallocState *s, size_t count, size_t size)
+static void *js_def_calloc(void *opaque, size_t count, size_t size)
 {
-    void *ptr;
-
-    /* Do not allocate zero bytes: behavior is platform dependent */
-    assert(count != 0 && size != 0);
-
-    if (size > 0)
-        if (unlikely(count != (count * size) / size))
-            return NULL;
-
-    /* When malloc_limit is 0 (unlimited), malloc_limit - 1 will be SIZE_MAX. */
-    if (unlikely(s->malloc_size + (count * size) > s->malloc_limit - 1))
-        return NULL;
-
-    ptr = calloc(count, size);
-    if (!ptr)
-        return NULL;
-
-    s->malloc_count++;
-    s->malloc_size += js__malloc_usable_size(ptr) + MALLOC_OVERHEAD;
-    return ptr;
+    return calloc(count, size);
 }
 
-static void *js_def_malloc(JSMallocState *s, size_t size)
+static void *js_def_malloc(void *opaque, size_t size)
 {
-    void *ptr;
-
-    /* Do not allocate zero bytes: behavior is platform dependent */
-    assert(size != 0);
-
-    /* When malloc_limit is 0 (unlimited), malloc_limit - 1 will be SIZE_MAX. */
-    if (unlikely(s->malloc_size + size > s->malloc_limit - 1))
-        return NULL;
-
-    ptr = malloc(size);
-    if (!ptr)
-        return NULL;
-
-    s->malloc_count++;
-    s->malloc_size += js__malloc_usable_size(ptr) + MALLOC_OVERHEAD;
-    return ptr;
+    return malloc(size);
 }
 
-static void js_def_free(JSMallocState *s, void *ptr)
+static void js_def_free(void *opaque, void *ptr)
 {
-    if (!ptr)
-        return;
-
-    s->malloc_count--;
-    s->malloc_size -= js__malloc_usable_size(ptr) + MALLOC_OVERHEAD;
     free(ptr);
 }
 
-static void *js_def_realloc(JSMallocState *s, void *ptr, size_t size)
+static void *js_def_realloc(void *opaque, void *ptr, size_t size)
 {
-    size_t old_size;
-
-    if (!ptr) {
-        if (size == 0)
-            return NULL;
-        return js_def_malloc(s, size);
-    }
-    if (unlikely(size == 0)) {
-        js_def_free(s, ptr);
-        return NULL;
-    }
-    old_size = js__malloc_usable_size(ptr);
-    /* When malloc_limit is 0 (unlimited), malloc_limit - 1 will be SIZE_MAX. */
-    if (s->malloc_size + size - old_size > s->malloc_limit - 1)
-        return NULL;
-
-    ptr = realloc(ptr, size);
-    if (!ptr)
-        return NULL;
-
-    s->malloc_size += js__malloc_usable_size(ptr) - old_size;
-    return ptr;
+    return realloc(ptr, size);
 }
 
 static const JSMallocFunctions def_malloc_funcs = {
@@ -2159,8 +2178,8 @@ void JS_FreeRuntime(JSRuntime *rt)
 #endif
 
     {
-        JSMallocState ms = rt->malloc_state;
-        rt->mf.js_free(&ms, rt);
+        JSMallocState *ms = &rt->malloc_state;
+        rt->mf.js_free(ms->opaque, rt);
     }
 }
 
diff --git a/quickjs.h b/quickjs.h
index 40be553..449b0a7 100644
--- a/quickjs.h
+++ b/quickjs.h
@@ -283,18 +283,11 @@ typedef JSValue JSCFunction(JSContext *ctx, JSValue this_val, int argc, JSValue
 typedef JSValue JSCFunctionMagic(JSContext *ctx, JSValue this_val, int argc, JSValue *argv, int magic);
 typedef JSValue JSCFunctionData(JSContext *ctx, JSValue this_val, int argc, JSValue *argv, int magic, JSValue *func_data);
 
-typedef struct JSMallocState {
-    size_t malloc_count;
-    size_t malloc_size;
-    size_t malloc_limit;
-    void *opaque; /* user opaque */
-} JSMallocState;
-
 typedef struct JSMallocFunctions {
-    void *(*js_calloc)(JSMallocState *s, size_t count, size_t size);
-    void *(*js_malloc)(JSMallocState *s, size_t size);
-    void (*js_free)(JSMallocState *s, void *ptr);
-    void *(*js_realloc)(JSMallocState *s, void *ptr, size_t size);
+    void *(*js_calloc)(void *opaque, size_t count, size_t size);
+    void *(*js_malloc)(void *opaque, size_t size);
+    void (*js_free)(void *opaque, void *ptr);
+    void *(*js_realloc)(void *opaque, void *ptr, size_t size);
     size_t (*js_malloc_usable_size)(const void *ptr);
 } JSMallocFunctions;