X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/f3718ac873cc4a8e6426f7fe1b0c88f004837c1a..0d7d86de4c0e32f716735817e799b90abd421402:/src/bindings/lua/simgrid_lua.c

diff --git a/src/bindings/lua/simgrid_lua.c b/src/bindings/lua/simgrid_lua.c
index 2002beac00..377773a16b 100644
--- a/src/bindings/lua/simgrid_lua.c
+++ b/src/bindings/lua/simgrid_lua.c
@@ -6,6 +6,7 @@
 /* This program is free software; you can redistribute it and/or modify it
  * under the terms of the license (GNU LGPL) which comes with this package. */
 #include "simgrid_lua.h"
+#include <string.h> // memcpy
 
 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(lua, bindings, "Lua Bindings");
 
@@ -19,7 +20,26 @@ static lua_State *lua_maestro_state;
 #define AS_MODULE_NAME "simgrid.AS"
 #define TRACE_MODULE_NAME "simgrid.Trace"
 
-static void stack_dump(const char *msg, lua_State *L);
+/**
+ * @brief A chunk of memory.
+ *
+ * TODO replace this by a dynar
+ */
+typedef struct s_buffer {
+  char* data;
+  size_t size;
+  size_t capacity;
+} s_buffer_t, *buffer_t;
+
+static const char* value_tostring(lua_State* L, int index);
+static const char* keyvalue_tostring(lua_State* L, int key_index, int value_index);
+static void stack_dump(const char *msg, lua_State* L);
+static int writer(lua_State* L, const void* source, size_t size, void* userdata);
+static lua_State* get_father(lua_State* L);
+static void move_value(lua_State* src, lua_State* dst);
+static void move_value_impl(lua_State* src, lua_State* dst, const char* name);
+static int l_get_from_father(lua_State* L);
+static lua_State *clone_lua_state(lua_State* L);
 static m_task_t check_task(lua_State *L, int index);
 static void register_c_functions(lua_State *L);
 
@@ -28,55 +48,639 @@ static void register_c_functions(lua_State *L);
 /* ********************************************************************************* */
 
 /**
- * @brief Dumps the Lua stack
+ * @brief Returns a string representation of a value in the Lua stack.
+ *
+ * This function is for debugging purposes.
+ * It always returns the same pointer.
+ *
+ * @param L the Lua state
+ * @param index index in the stack
+ * @return a string representation of the value at this index
+ */
+static const char* value_tostring(lua_State* L, int index) {
+
+  static char buff[64];
+
+  switch (lua_type(L, index)) {
+
+    case LUA_TNIL:
+      sprintf(buff, "nil");
+      break;
+
+    case LUA_TNUMBER:
+      sprintf(buff, "%.3f", lua_tonumber(L, index));
+      break;
+
+    case LUA_TBOOLEAN:
+      sprintf(buff, "%s", lua_toboolean(L, index) ? "true" : "false");
+      break;
+
+    case LUA_TSTRING:
+      snprintf(buff, 63, "'%s'", lua_tostring(L, index));
+      break;
+
+    case LUA_TFUNCTION:
+      if (lua_iscfunction(L, index)) {
+        sprintf(buff, "C-function");
+      }
+      else {
+        sprintf(buff, "function");
+      }
+      break;
+
+    case LUA_TTABLE:
+      sprintf(buff, "table(%p)", lua_topointer(L, index));
+      break;
+
+    case LUA_TLIGHTUSERDATA:
+    case LUA_TUSERDATA:
+      sprintf(buff, "userdata(%p)", lua_touserdata(L, index));
+      break;
+
+    case LUA_TTHREAD:
+      sprintf(buff, "thread");
+      break;
+  }
+  return buff;
+}
+
+/**
+ * @brief Returns a string representation of a key-value pair.
+ *
+ * This function is for debugging purposes.
+ * It always returns the same pointer.
+ *
+ * @param L the Lua state
+ * @param key_index index of the key
+ * @param value_index index of the value
+ * @return a string representation of the key-value pair
+ */
+static const char* keyvalue_tostring(lua_State* L, int key_index, int value_index) {
+
+  static char buff[64];
+  /* value_tostring also always returns the same pointer */
+  int len = snprintf(buff, 63, "[%s] -> ", value_tostring(L, key_index));
+  snprintf(buff + len, 63 - len, "%s", value_tostring(L, value_index));
+  return buff;
+}
+
+/**
+ * @brief Returns a string composed of the specified number of spaces.
+ *
+ * This function is for debugging purposes.
+ * It always returns the same pointer.
+ *
+ * @param length length of the string
+ * @return a string of this length with only spaces
+ */
+static const char* get_spaces(int length) {
+
+  static char spaces[128];
+
+  xbt_assert(length < 128);
+  memset(spaces, ' ', length);
+  spaces[length] = '\0';
+  return spaces;
+}
+
+/**
+ * @brief Dumps the Lua stack if debug logs are enabled.
  * @param msg a message to print
  * @param L a Lua state
  */
-static void stack_dump(const char *msg, lua_State *L)
+static void stack_dump(const char* msg, lua_State* L)
 {
-  char buff[2048];
-  char *p = buff;
-  int i;
-  int top = lua_gettop(L);
+  if (XBT_LOG_ISENABLED(lua, xbt_log_priority_debug)) {
+    char buff[2048];
+    char* p = buff;
+    int i;
+    int top = lua_gettop(L);
+
+    //if (1) return;
+
+    fflush(stdout);
+
+    p[0] = '\0';
+    for (i = 1; i <= top; i++) {  /* repeat for each level */
+
+      p += sprintf(p, "%s", value_tostring(L, i));
+      p += sprintf(p, " ");       /* put a separator */
+    }
+    XBT_DEBUG("%s%s", msg, buff);
+  }
+}
+
+/**
+ * @brief Writes the specified data into a memory buffer.
+ *
+ * This function is a valid lua_Writer that writes into a memory buffer passed
+ * as userdata.
+ *
+ * @param L a lua state
+ * @param source some data
+ * @param sz number of bytes of data
+ * @param user_data the memory buffer to write
+ */
+static int writer(lua_State* L, const void* source, size_t size, void* userdata) {
+
+  buffer_t buffer = (buffer_t) userdata;
+  while (buffer->capacity < buffer->size + size) {
+    buffer->capacity *= 2;
+    buffer->data = xbt_realloc(buffer->data, buffer->capacity);
+  }
+  memcpy(buffer->data + buffer->size, source, size);
+  buffer->size += size;
+
+  return 0;
+}
+
+/**
+ * @brief Returns the father of a state.
+ * @param L a Lua state
+ * @return its father
+ */
+static lua_State* get_father(lua_State* L) {
+
+                                  /* ... */
+  lua_pushstring(L, "simgrid.father");
+                                  /* ... "simgrid.father" */
+  lua_rawget(L, LUA_REGISTRYINDEX);
+                                  /* ... father */
+  lua_State* father = lua_touserdata(L, -1);
+  lua_pop(L, 1);
+                                  /* ... */
+  return father;
+}
+
+/**
+ * @brief Pops a value from a state and pushes it onto the stack of another
+ * state.
+ *
+ * @param src the source state
+ * @param dst the destination state
+ */
+static void move_value(lua_State* src, lua_State* dst) {
+
+  if (src != dst) {
+
+    /* get the list of visited tables from father at index 1 of dst */
+                                  /* src: ... value
+                                     dst: ... */
+    lua_getfield(dst, LUA_REGISTRYINDEX, "simgrid.father_visited_tables");
+                                  /* dst: ... visited */
+    lua_insert(dst, 1);
+                                  /* dst: visited ... */
+
+    move_value_impl(src, dst, value_tostring(src, -1));
+                                  /* src: ...
+                                     dst: visited ... value */
+    lua_remove(dst, 1);
+                                  /* dst: ... value */
+    stack_dump("src after xmove: ", src);
+    stack_dump("dst after xmove: ", dst);
+  }
+}
+
+/**
+ * @brief Pops a value from the stack of a source state and pushes it on the
+ * stack of another state.
+ *
+ * If the value is a table, its content is copied recursively. To avoid cycles,
+ * a table of previously visited tables must be present at index 1 of dst.
+ * Its keys are pointers to visited tables in src and its values are the tables
+ * already built.
+ *
+ * TODO: add support of closures
+ *
+ * @param src the source state
+ * @param dst the destination state, with a list of visited tables at index 1
+ * @param name a name describing the value
+ */
+static void move_value_impl(lua_State* src, lua_State *dst, const char* name) {
+
+  luaL_checkany(src, -1);                  /* check the value to copy */
+  luaL_checktype(dst, 1, LUA_TTABLE);      /* check the presence of a table of
+                                              previously visited tables */
 
-  fflush(stdout);
-  p += sprintf(p, "STACK(top=%d): ", top);
+  int indent = (lua_gettop(dst) - 1) * 6;
+  XBT_DEBUG("%sCopying data %s", get_spaces(indent), name);
+  indent += 2;
+
+  stack_dump("src before copying a value (should be ... value): ", src);
+  stack_dump("dst before copying a value (should be visited ...): ", dst);
+
+  switch (lua_type(src, -1)) {
+
+    case LUA_TNIL:
+      lua_pushnil(dst);
+      break;
 
-  for (i = 1; i <= top; i++) {  /* repeat for each level */
-    int t = lua_type(L, i);
-    switch (t) {
+    case LUA_TNUMBER:
+      lua_pushnumber(dst, lua_tonumber(src, -1));
+      break;
 
-    case LUA_TSTRING:          /* strings */
-      p += sprintf(p, "`%s'", lua_tostring(L, i));
+    case LUA_TBOOLEAN:
+      lua_pushboolean(dst, lua_toboolean(src, -1));
       break;
 
-    case LUA_TBOOLEAN:         /* booleans */
-      p += sprintf(p, lua_toboolean(L, i) ? "true" : "false");
+    case LUA_TSTRING:
+      /* no worries about memory: lua_pushstring makes a copy */
+      lua_pushstring(dst, lua_tostring(src, -1));
       break;
 
-    case LUA_TNUMBER:          /* numbers */
-      p += sprintf(p, "%g", lua_tonumber(L, i));
+    case LUA_TFUNCTION:
+      /* it's a function that does not exist yet in L2 */
+
+      if (lua_iscfunction(src, -1)) {
+        /* it's a C function: just copy the pointer */
+        lua_CFunction f = lua_tocfunction(src, -1);
+        lua_pushcfunction(dst, f);
+      }
+      else {
+        /* it's a Lua function: dump it from src */
+        XBT_DEBUG("%sDumping Lua function '%s'", get_spaces(indent), name);
+
+        s_buffer_t buffer;
+        buffer.capacity = 64;
+        buffer.size = 0;
+        buffer.data = xbt_new(char, buffer.capacity);
+
+        /* copy the binary chunk from src into a buffer */
+        int error = lua_dump(src, writer, &buffer);
+        xbt_assert(!error, "Failed to dump function '%s' from the source state: error %d",
+              name, error);
+
+        /* load the chunk into dst */
+        error = luaL_loadbuffer(dst, buffer.data, buffer.size, name);
+        xbt_assert(!error, "Failed to load function '%s' into the destination state: %s",
+            name, lua_tostring(dst, -1));
+        XBT_DEBUG("%sFunction '%s' successfully loaded", get_spaces(indent), name);
+      }
       break;
 
     case LUA_TTABLE:
-      p += sprintf(p, "Table");
+
+      /* first register the table in the source state itself */
+      lua_getfield(src, LUA_REGISTRYINDEX, "simgrid.visited_tables");
+                                  /* src: ... table visited */
+      lua_pushlightuserdata(src, (void*) lua_topointer(src, -1));
+                                  /* src: ... table visited psrctable */
+      lua_pushvalue(src, -3);
+                                  /* src: ... table visited psrctable table */
+      lua_settable(src, -3);
+                                  /* src: ... table visited */
+      lua_pop(src, 1);
+                                  /* src: ... table */
+
+      /* see if this table was already known by dst */
+      lua_pushlightuserdata(dst, (void*) lua_topointer(src, -1));
+                                  /* dst: visited ... psrctable */
+      lua_gettable(dst, 1);
+                                  /* dst: visited ... table/nil */
+      if (lua_istable(dst, -1)) {
+        XBT_DEBUG("%sNothing to do: table already visited (%p)",
+            get_spaces(indent), lua_topointer(src, -1));
+                                  /* dst: visited ... table */
+      }
+      else {
+        XBT_DEBUG("%sFirst visit of this table (%p)", get_spaces(indent),
+            lua_topointer(src, -1));
+                                  /* dst: visited ... nil */
+        lua_pop(dst, 1);
+                                  /* dst: visited ... */
+
+        /* first visit: create the new table in dst */
+        lua_newtable(dst);
+                                  /* dst: visited ... table */
+
+        /* mark the table as visited to avoid infinite recursion */
+        lua_pushlightuserdata(dst, (void*) lua_topointer(src, -1));
+                                  /* dst: visited ... table psrctable */
+        lua_pushvalue(dst, -2);
+                                  /* dst: visited ... table psrctable table */
+        lua_settable(dst, 1);
+                                  /* dst: visited ... table */
+        XBT_DEBUG("%sTable marked as visited", get_spaces(indent));
+
+        stack_dump("dst after marking the table as visited (should be visited ... table): ", dst);
+
+        /* copy the metatable if any */
+        int has_meta_table = lua_getmetatable(src, -1);
+                                  /* src: ... table mt? */
+        if (has_meta_table) {
+          XBT_DEBUG("%sCopying metatable", get_spaces(indent));
+                                  /* src: ... table mt */
+          move_value_impl(src, dst, "metatable");
+                                  /* src: ... table
+                                     dst: visited ... table mt */
+          lua_setmetatable(dst, -2);
+                                  /* dst: visited ... table */
+        }
+        else {
+          XBT_DEBUG("%sNo metatable", get_spaces(indent));
+        }
+
+        stack_dump("src before traversing the table (should be ... table): ", src);
+        stack_dump("dst before traversing the table (should be visited ... table): ", dst);
+
+        /* traverse the table of src and copy each element */
+        lua_pushnil(src);
+                                  /* src: ... table nil */
+        while (lua_next(src, -2) != 0) {
+                                  /* src: ... table key value */
+
+          XBT_DEBUG("%sCopying table element %s", get_spaces(indent), keyvalue_tostring(src, -2, -1));
+
+          stack_dump("src before copying table element (should be ... table key value): ", src);
+          stack_dump("dst before copying table element (should be visited ... table): ", dst);
+
+          /* copy the key */
+          lua_pushvalue(src, -2);
+                                  /* src: ... table key value key */
+          indent += 2;
+          XBT_DEBUG("%sCopying the key part of the table element", get_spaces(indent));
+          move_value_impl(src, dst, value_tostring(src, -1));
+                                  /* src: ... table key value
+                                     dst: visited ... table key */
+          XBT_DEBUG("%sCopied the key part of the table element", get_spaces(indent));
+
+          /* copy the value */
+          XBT_DEBUG("%sCopying the value part of the table element", get_spaces(indent));
+          move_value_impl(src, dst, value_tostring(src, -1));
+                                  /* src: ... table key
+                                     dst: visited ... table key value */
+          XBT_DEBUG("%sCopied the value part of the table element", get_spaces(indent));
+          indent -= 2;
+
+          /* set the table element */
+          lua_settable(dst, -3);
+                                  /* dst: visited ... table */
+
+          /* the key stays on top of src for next iteration */
+          stack_dump("src before next iteration (should be ... table key): ", src);
+          stack_dump("dst before next iteration (should be visited ... table): ", dst);
+
+          XBT_DEBUG("%sTable element copied", get_spaces(indent));
+        }
+        XBT_DEBUG("%sFinished traversing the table", get_spaces(indent));
+      }
       break;
 
-    default:                   /* other values */
-      p += sprintf(p, "???");
-/*      if ((ptr = luaL_checkudata(L,i,TASK_MODULE_NAME))) {
-        p+=sprintf(p,"task");
-      } else {
-        p+=printf(p,"%s", lua_typename(L, t));
-      }*/
+    case LUA_TLIGHTUSERDATA:
+      lua_pushlightuserdata(dst, lua_touserdata(src, -1));
       break;
 
+    case LUA_TUSERDATA:
+    {
+      /* copy the data */
+                                  /* src: ... udata
+                                     dst: visited ... */
+      size_t size = lua_objlen(src, -1);
+      void* src_block = lua_touserdata(src, -1);
+      void* dst_block = lua_newuserdata(dst, size);
+                                  /* dst: visited ... udata */
+      memcpy(dst_block, src_block, size);
+
+      /* copy the metatable if any */
+      int has_meta_table = lua_getmetatable(src, -1);
+                                  /* src: ... udata mt? */
+      if (has_meta_table) {
+        XBT_DEBUG("%sCopying metatable of userdata (%p)", get_spaces(indent),
+            lua_topointer(src, -1));
+                                  /* src: ... udata mt */
+        lua_State* father = get_father(dst);
+
+        if (father != NULL) {
+          XBT_DEBUG("%sGet the metatable from my father", get_spaces(indent));
+          /* find the same metatable in the father state */
+          /* TODO find in visited_tables of src the pointer to the same
+           * metatable in the father world, then copy the metatable from the
+           * father world into dst
+           */
+          lua_pushstring(father, "simgrid.visited_tables");
+                                  /* father: ... "simgrid.visited_tables" */
+          lua_rawget(father, LUA_REGISTRYINDEX);
+                                  /* father: ... visited */
+          lua_pushlightuserdata(father, (void*) lua_topointer(src, -1));
+                                  /* father: ... visited pfathermt */
+          lua_gettable(father, -2);
+                                  /* father: ... visited mt */
+          move_value_impl(father, dst, "(father metatable)");
+                                  /* father: ... visited
+                                     dst: visited ... udata mt */
+          lua_pop(father, 1);
+                                  /* father: ... */
+        }
+        else {
+          XBT_DEBUG("%sI have no father", get_spaces(indent));
+          move_value_impl(src, dst, "metatable");
+                                  /* src: ... udata
+                                     dst: visited ... udata mt */
+        }
+        lua_setmetatable(dst, -2);
+                                  /* dst: visited ... udata */
+
+        XBT_DEBUG("%sMetatable of userdata copied", get_spaces(indent));
+      }
+      else {
+        XBT_DEBUG("%sNo metatable for this userdata", get_spaces(indent));
+                                  /* src: ... udata */
+      }
     }
-    p += sprintf(p, "  ");      /* put a separator */
+    break;
+
+    case LUA_TTHREAD:
+      XBT_WARN("Cannot copy a thread from the source state.");
+      lua_pushnil(dst);
+      break;
   }
-  XBT_INFO("%s%s", msg, buff);
+
+  /* pop the value from src */
+  lua_pop(src, 1);
+
+  indent -= 2;
+  XBT_DEBUG("%sData copied", get_spaces(indent));
+
+  stack_dump("src after copying a value (should be ...): ", src);
+  stack_dump("dst after copying a value (should be visited ... value): ", dst);
 }
 
+/**
+ * @brief Copies a global value or a registry value from the father state.
+ *
+ * The state L must have a father, i.e. it should have been created by
+ * clone_lua_state().
+ * This function is meant to be an __index metamethod.
+ * Consequently, it assumes that the stack has two elements:
+ * a table (either the environment or the registry of L) and the string key of
+ * a value that does not exist yet in this table. It copies the corresponding
+ * value from the father state and pushes it on the stack of L.
+ * If the value does not exist in the father state either, nil is pushed.
+ *
+ * TODO: make this function thread safe. If the simulation runs in parallel,
+ * several simulated processes may trigger this __index metamethod at the same
+ * time and get globals from maestro.
+ *
+ * @param L the current state
+ * @return number of return values pushed (always 1)
+ */
+static int l_get_from_father(lua_State *L) {
+
+  /* check the arguments */
+  luaL_checktype(L, 1, LUA_TTABLE);
+  const char* key = luaL_checkstring(L, 2);
+                                               /* L:      table key */
+  XBT_DEBUG("__index of '%s' begins", key);
+
+  /* want a global or a registry value? */
+  int pseudo_index;
+  if (lua_equal(L, 1, LUA_REGISTRYINDEX)) {
+    /* registry */
+    pseudo_index = LUA_REGISTRYINDEX;
+    XBT_DEBUG("Will get the value from the registry of the father");
+  }
+  else {
+    /* global */
+    pseudo_index = LUA_GLOBALSINDEX;
+    XBT_DEBUG("Will get the value from the globals of the father");
+  }
+
+  /* get the father */
+  lua_State* father = get_father(L);
+
+  if (father == NULL) {
+    XBT_WARN("This state has no father");
+    lua_pop(L, 3);
+    lua_pushnil(L);
+    return 1;
+  }
+                                               /* L:      table key */
+
+  /* get the list of visited tables */
+  lua_pushstring(L, "simgrid.father_visited_tables");
+                                               /* L:      table key "simgrid.father_visited_tables" */
+  lua_rawget(L, LUA_REGISTRYINDEX);
+                                               /* L:      table key visited */
+  lua_insert(L, 1);
+                                               /* L:      visited table key */
+
+  /* get the value from the father */
+  lua_getfield(father, pseudo_index, key);
+                                               /* father: ... value */
+
+  /* push the value onto the stack of L */
+  move_value_impl(father, L, key);
+                                               /* father: ...
+                                                  L:      visited table key value */
+  lua_remove(L, 1);
+                                               /* L:      table key value */
+
+  /* prepare the return value of __index */
+  lua_pushvalue(L, -1);
+                                               /* L:      table key value value */
+  lua_insert(L, 1);
+                                               /* L:      value table key value */
+
+  /* save the copied value in the table for subsequent accesses */
+  lua_settable(L, -3);
+                                               /* L:      value table */
+  lua_settop(L, 1);
+                                               /* L:      value */
+
+  XBT_DEBUG("__index of '%s' returns %s", key, value_tostring(L, -1));
+
+  return 1;
+}
+
+/**
+ * @brief Creates a new Lua state and get its environment from an existing state.
+ *
+ * The state created is independent from the existing one and has its own
+ * copies of global variables and functions.
+ * However, the global variables and functions are not copied right now from
+ * the original state; they are copied only the first time they are accessed.
+ * This behavior saves time and memory, and is okay for Simgrid's needs.
+ *
+ * @param father an existing state
+ * @return the state created
+ */
+static lua_State* clone_lua_state(lua_State *father) {
+
+  /* create the new state */
+  lua_State *L = luaL_newstate();
+
+  /* set its environment and its registry:
+   * - create a table newenv
+   * - create a metatable mt
+   * - set mt.__index = a function that copies the global from the father state
+   * - set mt as the metatable of the registry
+   * - set mt as the metatable of newenv
+   * - set newenv as the environment of the new state
+   */
+  lua_pushthread(L);                        /* thread */
+  lua_newtable(L);                          /* thread newenv */
+  lua_newtable(L);                          /* thread newenv mt */
+  lua_pushvalue(L, LUA_REGISTRYINDEX);      /* thread newenv mt reg */
+  lua_pushcfunction(L, l_get_from_father);  /* thread newenv mt reg f */
+  lua_setfield(L, -3, "__index");           /* thread newenv mt reg */
+  lua_pushvalue(L, -2);                     /* thread newenv mt reg mt */
+  lua_setmetatable(L, -2);                  /* thread newenv mt reg */
+  lua_pop(L, 1);                            /* thread newenv mt */
+  lua_setmetatable(L, -2);                  /* thread newenv */
+  lua_setfenv(L, -2);                       /* thread */
+  lua_pop(L, 1);                            /* -- */
+
+  /* set a pointer to the father */
+  lua_pushstring(L, "simgrid.father");      /* "simgrid.father" */
+  lua_pushlightuserdata(L, father);         /* "simgrid.father" father */
+  lua_rawset(L, LUA_REGISTRYINDEX);
+                                            /* -- */
+
+  /* create the table of visited tables from the father */
+  lua_pushstring(L, "simgrid.father_visited_tables");
+                                            /* "simgrid.father_visited_tables" */
+  lua_newtable(L);                          /* "simgrid.father_visited_tables" visited */
+  lua_rawset(L, LUA_REGISTRYINDEX);
+                                            /* -- */
+
+  /* create the table of my own visited tables */
+  /* TODO simgrid.father_visited_tables probably becomes useless */
+  lua_pushstring(L, "simgrid.visited_tables");
+                                            /* "simgrid.visited_tables" */
+  lua_newtable(L);                          /* "simgrid.visited_tables" visited */
+  lua_rawset(L, LUA_REGISTRYINDEX);
+                                            /* -- */
+
+  /* open the standard libs (theoretically, this is not necessary as they can
+   * be inherited like any global values, but without a proper support of
+   * closures, iterators like ipairs don't work). */
+  XBT_DEBUG("Metatable of globals and registry set, opening standard libraries now");
+  luaL_openlibs(L);
+
+  XBT_DEBUG("New state created");
+
+  return L;
+}
+
+/*
+static void *my_checkudata (lua_State *L, int ud, const char *tname) {
+  void *p = lua_touserdata(L, ud);
+  lua_getfield(L, LUA_REGISTRYINDEX, tname);
+  const void* correct_mt = lua_topointer(L, -1);
+
+  int has_mt = lua_getmetatable(L, ud);
+  const void* actual_mt = NULL;
+  if (has_mt) { actual_mt = lua_topointer(L, -1); lua_pop(L, 1); }
+  XBT_DEBUG("Checking the task's metatable: expected %p, found %p", correct_mt, actual_mt);
+  stack_dump("my_checkudata: ", L);
+
+  if (p == NULL || !lua_getmetatable(L, ud) || !lua_rawequal(L, -1, -2))
+    luaL_typerror(L, ud, tname);
+  lua_pop(L, 2);
+  return p;
+}
+*/
+
 /**
  * @brief Ensures that a userdata on the stack is a task
  * and returns the pointer inside the userdata.
@@ -89,7 +693,9 @@ static m_task_t checkTask(lua_State * L, int index)
   m_task_t *pi, tk;
   luaL_checktype(L, index, LUA_TTABLE);
   lua_getfield(L, index, "__simgrid_task");
-  pi = (m_task_t *) luaL_checkudata(L, -1, TASK_MODULE_NAME);
+
+  pi = (m_task_t *) luaL_checkudata(L, lua_gettop(L), TASK_MODULE_NAME);
+
   if (pi == NULL)
     luaL_typerror(L, index, TASK_MODULE_NAME);
   tk = *pi;
@@ -179,7 +785,7 @@ static int Task_destroy(lua_State * L)
 
 static int Task_send(lua_State * L)
 {
-  //stackDump("send ",L);
+  //stack_dump("send ", L);
   m_task_t tk = checkTask(L, 1);
   const char *mailbox = luaL_checkstring(L, 2);
   lua_pop(L, 1);                // remove the string so that the task is on top of it
@@ -216,7 +822,15 @@ static int Task_recv_with_timeout(lua_State *L)
 
   if (res == MSG_OK) {
     lua_State *sender_stack = MSG_task_get_data(tk);
-    lua_xmove(sender_stack, L, 1);        // copy the data directly from sender's stack
+
+    stack_dump("sender before moving data: ", sender_stack);
+    stack_dump("receiver before moving data: ", L);
+
+    move_value(sender_stack, L);        // copy the data directly from sender's stack
+
+    stack_dump("sender after moving data: ", sender_stack);
+    stack_dump("receiver after moving data: ", L);
+
     MSG_task_set_data(tk, NULL);
   }
   else {
@@ -285,7 +899,7 @@ static m_host_t checkHost(lua_State * L, int index)
   m_host_t *pi, ht;
   luaL_checktype(L, index, LUA_TTABLE);
   lua_getfield(L, index, "__simgrid_host");
-  pi = (m_host_t *) luaL_checkudata(L, -1, HOST_MODULE_NAME);
+  pi = (m_host_t *) luaL_checkudata(L, lua_gettop(L), HOST_MODULE_NAME);
   if (pi == NULL)
     luaL_typerror(L, index, HOST_MODULE_NAME);
   ht = *pi;
@@ -555,11 +1169,10 @@ static int run_lua_code(int argc, char **argv)
 {
   XBT_DEBUG("Run lua code %s", argv[0]);
 
-  lua_State *L = lua_newthread(lua_maestro_state);
-  int ref = luaL_ref(lua_maestro_state, LUA_REGISTRYINDEX);     /* protect the thread from being garbage collected */
+  lua_State *L = clone_lua_state(lua_maestro_state);
   int res = 1;
 
-  /* start the co-routine */
+  /* start the function */
   lua_getglobal(L, argv[0]);
   xbt_assert(lua_isfunction(L, -1),
               "The lua function %s does not seem to exist", argv[0]);
@@ -581,8 +1194,6 @@ static int run_lua_code(int argc, char **argv)
     lua_pop(L, 1);              /* pop returned value */
   }
 
-  /* cleanups */
-  luaL_unref(lua_maestro_state, LUA_REGISTRYINDEX, ref);
   XBT_DEBUG("Execution of Lua code %s is over", (argv ? argv[0] : "(null)"));
 
   return res;
@@ -772,6 +1383,10 @@ int luaopen_simgrid(lua_State *L)
   /* Keep the context mechanism informed of our lua world today */
   lua_maestro_state = L;
 
+  /* initialize access to my tables by children Lua states */
+  lua_newtable(L);
+  lua_setfield(L, LUA_REGISTRYINDEX, "simgrid.visited_tables");
+
   register_c_functions(L);
 
   return 1;