🐛 fix issue #80

Signed-off-by: ValKmjolnir <lhk101lhk101@qq.com>

src/nasal_gc.cpp

@@ -33,8 +33,11 @@ void gc::mark() {
     while (!bfs.empty()) {
         var value = bfs.front();
         bfs.pop();
-        if (value.type <= vm_type::vm_num ||
-            value.val.gcobj->mark != nas_val::gc_status::uncollected) {
+        if (value.type <= vm_type::vm_num) {
+            continue;
+        }
+        if (value.val.gcobj->mark != nas_val::gc_status::uncollected &&
+            value.val.gcobj->mark != nas_val::gc_status::alloc_in_sweep_stage) {
             continue;
         }
         mark_var(bfs, value);
@@ -170,7 +173,8 @@ void gc::sweep() {
         if (i->mark == nas_val::gc_status::uncollected) {
             unused[static_cast<u32>(i->type) - static_cast<u32>(vm_type::vm_str)].push_back(i);
             i->mark = nas_val::gc_status::collected;
-        } else if (i->mark == nas_val::gc_status::found) {
+        } else if (i->mark == nas_val::gc_status::found ||
+                   i->mark == nas_val::gc_status::alloc_in_sweep_stage) {
             i->mark = nas_val::gc_status::uncollected;
         }
     }
@@ -297,10 +301,14 @@ var gc::alloc(const vm_type type) {
     var ret = var::gcobj(unused[index].back());
     ret.val.gcobj->clear();
 
-    // if incremental sweep stage, mark it as found
-    // but be aware that it may be collected in next gc cycle
+    // if incremental sweep stage, mark it with special state.
+    // to avoid miss-marking objects inside them, because mark stage
+    // will skip scanning objects with "found" mark
+    // if we mark it with "found" mark, objects inside it will not be marked
+    // so they may be treated as unreferenced, which is not expected.
+    // be aware that it will be collected in next gc cycle
     ret.val.gcobj->mark = in_incremental_sweep_stage
-        ? nas_val::gc_status::found
+        ? nas_val::gc_status::alloc_in_sweep_stage
         : nas_val::gc_status::uncollected;
     unused[index].pop_back();
     return ret;

src/nasal_gc.h

@@ -66,7 +66,7 @@ struct gc {
     const u64 max_incr[GC_TYPE_SIZE] = {
         8192, // vm_str
         8192, // vm_vec
-        4096, // vm_hash
+        8192, // vm_hash
         2048, // vm_func
         2048, // vm_upval
         256,  // vm_obj

src/nasal_type.h

@@ -51,9 +51,12 @@ struct nas_map;   // mapper
 // nas_val includes gc-managed types
 struct nas_val {
     enum class gc_status: u8 {
-        uncollected = 0,
-        collected,
-        found
+        uncollected = 0,     // will be collected by sweep
+        collected,           // already collected and put into unused list
+        found,               // marked as referenced
+        alloc_in_sweep_stage // mark it allocated in incremental sweep stage
+                             // still scan in mark stage
+                             // but do not sweep in this gc cycle
     };
 
     gc_status mark;

test/gc_test.nas

@@ -24,10 +24,7 @@ var test_func = func(test_processes...) {
     var end_info = runtime.gc.info();
     var gc_total_end = end_info.total;
     var duration = time_stamp.elapsedMSec();
-    if (duration == nil) {
-        println(time_stamp.elapsedMSec);
-        die("remaining issue: time_stamp.elapsedMSec() entry = 0x559.");
-    }
+
     print(" ", duration, " ms,\tgc ",
         int((gc_total_end-gc_total_begin)*100/duration), "%,\t",
         int(1000/(duration/size(test_processes))*10)/10, " test(s)/sec",
@@ -113,7 +110,8 @@ var append_tree = func {
         append(res, {
             a: {b: {c:[1, 2, 3, 4]}},
             d: {e: {}},
-            j: {k: {l:{m:[{a:{b:{c:[{}, {}]}}}]}}}
+            j: {k: {l:{m:[{a:{b:{c:[{}, {}]}}}]}}},
+            n: [[], []]
         });
     }
 }
@@ -122,12 +120,12 @@ var append_deep_tree = func {
     var res = {};
     var tmp = [];
     for (var i = 0; i < MAX_ITER_NUM; i += 1) {
-        tmp = [[[tmp]]];
+        tmp = [[[tmp, tmp]]];
     }
     res["vec"] = tmp;
     tmp = {};
     for (var i = 0; i < MAX_ITER_NUM; i += 1) {
-        tmp = {a : {a : {a : tmp}}};
+        tmp = {a : {a : {a : tmp, b : tmp}}};
     }
     res["hash"] = tmp;
     return res;