stack overflow, and realloc bug fixed

stack realloc wasn't update the next callframe's base pointer which
caused a crash which is fixed

infinit recursions are now handled properly. now it'll dump the stack
frames and exit properly

src/pk_debug.c

@@ -170,22 +170,19 @@ void reportCompileTimeError(PKVM* vm, const char* path, int line,
   pkByteBufferClear(&buff, vm);
 }
 
-void reportRuntimeError(PKVM* vm, Fiber* fiber) {
+static void _reportStackFrame(PKVM* vm, CallFrame* frame) {
-
   pkWriteFn writefn = vm->config.stderr_write;
-  if (writefn == NULL) return;
-
-  // Error message.
-  _printRed(vm, "Error: ");
-  writefn(vm, fiber->error->data);
-  writefn(vm, "\n");
-
-  // Stack trace.
-  for (int i = fiber->frame_count - 1; i >= 0; i--) {
-    CallFrame* frame = &fiber->frames[i];
   const Function* fn = frame->closure->fn;
   ASSERT(!fn->is_native, OOPS);
-    int line = fn->fn->oplines.data[frame->ip - fn->fn->opcodes.data - 1];
+
+  // After fetching the instruction the ip will be inceased so we're
+  // reducing it by 1. But stack overflows are occure before executing
+  // any instruction of that function, so the instruction_index possibly
+  // be -1 (set it to zero in that case).
+  int instruction_index = frame->ip - fn->fn->opcodes.data - 1;
+  if (instruction_index == -1) instruction_index++;
+
+  int line = fn->fn->oplines.data[instruction_index];
 
   if (fn->owner->path == NULL) {
 
@@ -208,8 +205,48 @@ void reportRuntimeError(PKVM* vm, Fiber* fiber) {
     writefn(vm, buff);
     writefn(vm, "]\n");
   }
-
 }
+
+void reportRuntimeError(PKVM* vm, Fiber* fiber) {
+
+  pkWriteFn writefn = vm->config.stderr_write;
+  if (writefn == NULL) return;
+
+  // Error message.
+  _printRed(vm, "Error: ");
+  writefn(vm, fiber->error->data);
+  writefn(vm, "\n");
+
+  // If the stack frames are greater than 2 * max_dump_frames + 1,
+  // we're only print the first [max_dump_frames] and last [max_dump_frames]
+  // lines.
+  int max_dump_frames = 10;
+
+  if (fiber->frame_count > 2 * max_dump_frames) {
+    for (int i =  0; i < max_dump_frames; i++) {
+      CallFrame* frame = &fiber->frames[fiber->frame_count - 1 - i];
+      _reportStackFrame(vm, frame);
+    }
+
+    int skipped_count = fiber->frame_count - max_dump_frames * 2;
+    writefn(vm, "  ...  skipping ");
+    char buff[STR_INT_BUFF_SIZE];
+    sprintf(buff, "%d", skipped_count);
+    writefn(vm, buff);
+    writefn(vm, " stack frames\n");
+
+    for (int i = max_dump_frames; i >= 0; i--) {
+      CallFrame* frame = &fiber->frames[i];
+      _reportStackFrame(vm, frame);
+    }
+
+  } else {
+    for (int i = fiber->frame_count - 1; i >= 0; i--) {
+      CallFrame* frame = &fiber->frames[i];
+      _reportStackFrame(vm, frame);
+    }
+  }
+
 }
 
 // Opcode names array.

src/pk_internal.h

@@ -54,6 +54,11 @@
 // header for more information on Nan-tagging.
 #define VAR_NAN_TAGGING 1
 
+// The maximum size of the pocketlang stack. This value is arbitrary. currently
+// it's 800 KB. Change this to any value upto 2147483647 (signed integer max)
+// if you want.
+#define MAX_STACK_SIZE 1024 * 800
+
 // The maximum number of argument a pocketlang function supported to call. This
 // value is arbitrary and feel free to change it. (Just used this limit for an
 // internal buffer to store values before calling a new fiber).

src/pk_vm.c

@@ -333,8 +333,13 @@ static inline Var importModule(PKVM* vm, String* key) {
 
 void vmEnsureStackSize(PKVM* vm, int size) {
 
+  if (size >= (MAX_STACK_SIZE / sizeof(Var))) {
+    VM_SET_ERROR(vm, newString(vm, "Maximum stack limit reached."));
+    return;
+  }
+
   Fiber* fiber = vm->fiber;
-  if (fiber->stack_size > size) return;
+  if (fiber->stack_size >= size) return;
 
   int new_size = utilPowerOf2Ceil(size);
 
@@ -378,8 +383,11 @@ void vmEnsureStackSize(PKVM* vm, int size) {
   }
 }
 
-static inline void pushCallFrame(PKVM* vm, const Closure* closure, Var* rbp) {
+// The return address for the next call frame (rbp) has to be set to the
+// fiber's ret (fiber->ret == next rbp).
+static inline void pushCallFrame(PKVM* vm, const Closure* closure) {
   ASSERT(!closure->fn->is_native, OOPS);
+  ASSERT(vm->fiber->ret != NULL, OOPS);
 
   // Grow the stack frame if needed.
   if (vm->fiber->frame_count + 1 > vm->fiber->frame_capacity) {
@@ -391,12 +399,12 @@ static inline void pushCallFrame(PKVM* vm, const Closure* closure, Var* rbp) {
   }
 
   // Grow the stack if needed.
-  int needed = (closure->fn->fn->stack_size +
+  int current_stack_slots = (int)(vm->fiber->sp - vm->fiber->stack) + 1;
-                (int)(vm->fiber->sp - vm->fiber->stack));
+  int needed = closure->fn->fn->stack_size + current_stack_slots;
   vmEnsureStackSize(vm, needed);
 
   CallFrame* frame = vm->fiber->frames + vm->fiber->frame_count++;
-  frame->rbp = rbp;
+  frame->rbp = vm->fiber->ret;
   frame->closure = closure;
   frame->ip = closure->fn->fn->opcodes.data;
 
@@ -927,6 +935,8 @@ L_vm_main_loop:
 
         ASSERT(imported->body != NULL, OOPS);
 
+        UPDATE_FRAME(); //< Update the current frame's ip.
+
         // Note that we're setting the main function's return address to the
         // module itself (for every other function we'll push a null at the rbp
         // before calling them and it'll be returned without modified if the
@@ -934,11 +944,11 @@ L_vm_main_loop:
         // body of the module, so the main function will return what's at the
         // rbp without modifying it. So at the end of the main function the
         // stack top would be the module itself.
-        Var* module_ret = fiber->sp - 1;
+        fiber->ret = fiber->sp - 1;
+        pushCallFrame(vm, imported->body);
 
-        UPDATE_FRAME(); //< Update the current frame's ip.
-        pushCallFrame(vm, imported->body, module_ret);
         LOAD_FRAME();  //< Load the top frame to vm's execution variables.
+        CHECK_ERROR(); //< Stack overflow.
       }
 
       DISPATCH();
@@ -1076,8 +1086,9 @@ L_do_call:
                  (instruction == OP_SUPER_CALL), OOPS);
 
           UPDATE_FRAME(); //< Update the current frame's ip.
-          pushCallFrame(vm, closure, fiber->ret);
+          pushCallFrame(vm, closure);
           LOAD_FRAME();  //< Load the top frame to vm's execution variables.
+          CHECK_ERROR(); //< Stack overflow.
         }
       }