QJS hooks and GC hooks

quickjs.c

@@ -305,6 +305,9 @@ struct JSRuntime {
     void *user_opaque;
     void *libc_opaque;
     JSRuntimeFinalizerState *finalizers;
+
+    /* Unified handler for all the engine hooks */
+    JS_BOOL (*hooks)(JSRuntimeHooks type, void* opaque);
 };
 
 struct JSClass {
@@ -1440,7 +1443,17 @@ static void js_trigger_gc(JSRuntime *rt, size_t size)
                    (uint64_t)rt->malloc_state.malloc_size);
         }
 #endif
-        JS_RunGC(rt);
+        //To ensure JS_RunGC cannot be executed again within callbacks, disable and restore it after.
+        size_t tmp_threshold = rt->malloc_gc_threshold;
+        rt->malloc_gc_threshold=-1;
+
+        if((rt->hooks == NULL) || rt->hooks(JS_HOOK_GC_BEFORE,NULL)){
+            JS_RunGC(rt);
+            if(rt->hooks != NULL)rt->hooks(JS_HOOK_GC_AFTER,NULL);
+        }
+
+        rt->malloc_gc_threshold=tmp_threshold;
+
         rt->malloc_gc_threshold = rt->malloc_state.malloc_size +
             (rt->malloc_state.malloc_size >> 1);
     }
@@ -1810,6 +1823,8 @@ JSRuntime *JS_NewRuntime2(const JSMallocFunctions *mf, void *opaque)
     rt->malloc_state = ms;
     rt->malloc_gc_threshold = 256 * 1024;
 
+    rt->hooks = NULL;
+
     bf_context_init(&rt->bf_ctx, js_bf_realloc, rt);
 
     init_list_head(&rt->context_list);
@@ -1922,7 +1937,8 @@ void JS_SetDumpFlags(JSRuntime *rt, uint64_t flags)
     rt->dump_flags = flags;
 }
 
-size_t JS_GetGCThreshold(JSRuntime *rt) {
+size_t JS_GetGCThreshold(JSRuntime *rt)
+{
     return rt->malloc_gc_threshold;
 }
 
@@ -1932,6 +1948,11 @@ void JS_SetGCThreshold(JSRuntime *rt, size_t gc_threshold)
     rt->malloc_gc_threshold = gc_threshold;
 }
 
+void JS_SetHooksHandler(JSRuntime *rt, JS_BOOL (*fn)(JSRuntimeHooks type, void* opaque))
+{
+    rt->hooks = fn;
+}
+
 #define malloc(s) malloc_is_forbidden(s)
 #define free(p) free_is_forbidden(p)
 #define realloc(p,s) realloc_is_forbidden(p,s)

quickjs.h

@@ -324,6 +324,13 @@ typedef void JSRuntimeFinalizer(JSRuntime *rt, void *arg);
 
 typedef struct JSGCObjectHeader JSGCObjectHeader;
 
+/* Engine hooks */
+typedef enum JSRuntimeHooks{
+    JS_HOOK_NONE,           //Don't use, just to catch potential bugs
+    JS_HOOK_GC_BEFORE,      //Run before a GC event takes place. No payload. Return false if the hooks opposes the GC event to take place.
+    JS_HOOK_GC_AFTER,       //Run after a GC event took place. No payload. Return value ignored.
+} JSRuntimeHooks;
+
 JS_EXTERN JSRuntime *JS_NewRuntime(void);
 /* info lifetime must exceed that of rt */
 JS_EXTERN void JS_SetRuntimeInfo(JSRuntime *rt, const char *info);
@@ -332,6 +339,8 @@ JS_EXTERN void JS_SetMemoryLimit(JSRuntime *rt, size_t limit);
 JS_EXTERN void JS_SetDumpFlags(JSRuntime *rt, uint64_t flags);
 JS_EXTERN size_t JS_GetGCThreshold(JSRuntime *rt);
 JS_EXTERN void JS_SetGCThreshold(JSRuntime *rt, size_t gc_threshold);
+/* register a hook dispatcher for this runtime. The handler should always return true for hooks which are not supported. */
+JS_EXTERN void JS_SetHooksHandler(JSRuntime *rt, JS_BOOL (*fn)(JSRuntimeHooks type, void* opaque));
 /* use 0 to disable maximum stack size check */
 JS_EXTERN void JS_SetMaxStackSize(JSRuntime *rt, size_t stack_size);
 /* should be called when changing thread to update the stack top value