issue #163 First attempt to implement a Go like defer statement

include/ldo.h

@@ -54,6 +54,7 @@ LUAI_FUNC void luaD_inctop (lua_State *L);
 
 LUAI_FUNC l_noret luaD_throw (lua_State *L, int errcode);
 LUAI_FUNC int luaD_rawrunprotected (lua_State *L, Pfunc f, void *ud);
+LUAI_FUNC void luaD_seterrorobj (lua_State *L, int errcode, StkId oldtop);
 
 #endif
 

include/lfunc.h

@@ -35,7 +35,8 @@
 */
 struct UpVal {
   TValue *v;  /* points to stack or to its own value */
-  lu_mem refcount;  /* reference counter */
+  unsigned int refcount;  /* reference counter */
+  unsigned int flags; /* Used to mark deferred values */
   union {
     struct {  /* (when open) */
       UpVal *next;  /* linked list */
@@ -53,7 +54,7 @@ LUAI_FUNC CClosure *luaF_newCclosure (lua_State *L, int nelems);
 LUAI_FUNC LClosure *luaF_newLclosure (lua_State *L, int nelems);
 LUAI_FUNC void luaF_initupvals (lua_State *L, LClosure *cl);
 LUAI_FUNC UpVal *luaF_findupval (lua_State *L, StkId level);
-LUAI_FUNC void luaF_close (lua_State *L, StkId level);
+LUAI_FUNC int luaF_close (lua_State *L, StkId level, int status);
 LUAI_FUNC void luaF_freeproto (lua_State *L, Proto *f);
 /* The additional type argument is a Ravi extension */
 LUAI_FUNC const char *luaF_getlocalname (const Proto *func, int local_number,

include/llex.h

@@ -27,7 +27,7 @@ enum RESERVED {
   /* terminal symbols denoted by reserved words */
   TK_AND = FIRST_RESERVED, TK_BREAK,
   TK_DO, TK_ELSE, TK_ELSEIF, TK_END, TK_FALSE, TK_FOR, TK_FUNCTION,
-  TK_GOTO, TK_IF, TK_IN, TK_LOCAL, TK_NIL, TK_NOT, TK_OR, TK_REPEAT,
+  TK_GOTO, TK_IF, TK_IN, TK_LOCAL, TK_DEFER, TK_NIL, TK_NOT, TK_OR, TK_REPEAT,
   TK_RETURN, TK_THEN, TK_TRUE, TK_UNTIL, TK_WHILE,
   /* other terminal symbols */
   TK_IDIV, TK_CONCAT, TK_DOTS, TK_EQ, TK_GE, TK_LE, TK_NE,

include/lopcodes.h

@@ -281,10 +281,12 @@ OP_RAVI_SELF_SK,      /*	A B C	R(A+1) := R(B); R(A) := R(B)[RK(C)], string key *
 OP_RAVI_SETFIELD,     /*	A B C	R(A)[RK(B)] := RK(C), string key */
 OP_RAVI_GETTABUP_SK,  /*	A B C	R(A) := UpValue[B][RK(C)], string key */
 
+OP_RAVI_DEFER,        /*        A	mark variable A "deferred"	  */
+
 } OpCode;
 
 
-#define NUM_OPCODES	(cast(int, OP_RAVI_GETTABUP_SK) + 1)
+#define NUM_OPCODES	(cast(int, OP_RAVI_DEFER) + 1)
 
 /*===========================================================================
   Notes:

src/ldo.c

@@ -90,7 +90,7 @@ struct lua_longjmp {
 };
 
 
-static void seterrorobj (lua_State *L, int errcode, StkId oldtop) {
+void luaD_seterrorobj (lua_State *L, int errcode, StkId oldtop) {
   switch (errcode) {
     case LUA_ERRMEM: {  /* memory error? */
       setsvalue2s(L, oldtop, G(L)->memerrmsg); /* reuse preregistered msg. */
@@ -123,7 +123,7 @@ l_noret luaD_throw (lua_State *L, int errcode) {
     }
     else {  /* no handler at all; abort */
       if (g->panic) {  /* panic function? */
-        seterrorobj(L, errcode, L->top);  /* assume EXTRA_STACK */
+        luaD_seterrorobj(L, errcode, L->top);  /* assume EXTRA_STACK */
         if (L->ci->top < L->top)
           L->ci->top = L->top;  /* pushing msg. can break this invariant */
         lua_unlock(L);
@@ -713,8 +713,8 @@ static int recover (lua_State *L, int status) {
   if (ci == NULL) return 0;  /* no recovery point */
   /* "finish" luaD_pcall */
   oldtop = restorestack(L, ci->extra);
-  luaF_close(L, oldtop);
-  seterrorobj(L, status, oldtop);
+  luaF_close(L, oldtop, status);
+  luaD_seterrorobj(L, status, oldtop);
   L->ci = ci;
   L->allowhook = getoah(ci->callstatus);  /* restore original 'allowhook' */
   L->nny = 0;  /* should be zero to be yieldable */
@@ -800,7 +800,7 @@ LUA_API int lua_resume (lua_State *L, lua_State *from, int nargs) {
     }
     if (errorstatus(status)) {  /* unrecoverable error? */
       L->status = cast_byte(status);  /* mark thread as 'dead' */
-      seterrorobj(L, status, L->top);  /* push error message */
+      luaD_seterrorobj(L, status, L->top);  /* push error message */
       L->ci->top = L->top;
     }
     else lua_assert(status == L->status);  /* normal end or yield */
@@ -858,11 +858,12 @@ int luaD_pcall (lua_State *L, Pfunc func, void *u,
   status = luaD_rawrunprotected(L, func, u);
   if (status != LUA_OK) {  /* an error occurred? */
     StkId oldtop = restorestack(L, old_top);
-    luaF_close(L, oldtop);  /* close possible pending closures */
-    seterrorobj(L, status, oldtop);
     L->ci = old_ci;
     L->allowhook = old_allowhooks;
     L->nny = old_nny;
+    status = luaF_close(L, oldtop, status);  /* close possible pending closures */
+    oldtop = restorestack(L, old_top);
+    luaD_seterrorobj(L, status, oldtop);
     luaD_shrinkstack(L);
   }
   L->errfunc = old_errfunc;

src/lfunc.c

@@ -19,6 +19,7 @@
 
 #include "lua.h"
 
+#include "ldo.h"
 #include "lfunc.h"
 #include "lgc.h"
 #include "lmem.h"
@@ -66,13 +67,15 @@ UpVal *luaF_findupval (lua_State *L, StkId level) {
   lua_assert(isintwups(L) || L->openupval == NULL);
   while (*pp != NULL && (p = *pp)->v >= level) {
     lua_assert(upisopen(p));
-    if (p->v == level)  /* found a corresponding upvalue? */
-      return p;  /* return it */
+    if (p->v == level && !p->flags)  /* found a corresponding upvalue that is not a deferred value? */ {
+      return p; /* return it */
+    }
     pp = &p->u.open.next;
   }
   /* not found: create a new upvalue */
   uv = luaM_new(L, UpVal);
   uv->refcount = 0;
+  uv->flags = 0;
   uv->u.open.next = *pp;  /* link it to list of open upvalues */
   uv->u.open.touched = 1;
   *pp = uv;
@@ -84,20 +87,49 @@ UpVal *luaF_findupval (lua_State *L, StkId level) {
   return uv;
 }
 
+static void callclose (lua_State *L, void *ud) {
+  luaD_callnoyield(L, cast(StkId, ud), 0);
+}
 
-void luaF_close (lua_State *L, StkId level) {
+static int calldeferredfunction (lua_State *L, UpVal *uv, StkId level, int status) {
+  StkId func = level + 1;  /* save slot for old error message */
+  setobj2s(L, func, uv->v);  /* will call it */
+  if (status != LUA_OK)  /* was there an error? */
+    luaD_seterrorobj(L, status, level);  /* save error message */
+  else
+    setnilvalue(level);
+  setobjs2s(L, func + 1, level);  /* error msg. as argument */
+  L->top = func + 2;  /* add function and argument */
+  if (status == LUA_OK)  /* not in "error mode"? */
+    callclose(L, func);  /* call closing method */
+  else {  /* already inside error handler; cannot raise another error */
+    int newstatus = luaD_pcall(L, callclose, func, savestack(L, level), 0);
+    if (newstatus != LUA_OK)  /* error when closing? */
+      status = newstatus;  /* this will be the new error */
+  }
+  return status;
+}
+
+int luaF_close (lua_State *L, StkId level, int status) {
   UpVal *uv;
   while (L->openupval != NULL && (uv = L->openupval)->v >= level) {
     lua_assert(upisopen(uv));
     L->openupval = uv->u.open.next;  /* remove from 'open' list */
-    if (uv->refcount == 0)  /* no references? */
-      luaM_free(L, uv);  /* free upvalue */
+    if (uv->refcount == 0) {         /* no references? */
+      if (uv->flags && ttisfunction(uv->v)) {
+        ptrdiff_t levelrel = savestack(L, level);
+        status = calldeferredfunction(L, uv, uv->v, status);
+        level = restorestack(L, levelrel);
+      }
+      luaM_free(L, uv);              /* free upvalue */
+    }
     else {
       setobj(L, &uv->u.value, uv->v);  /* move value to upvalue slot */
       uv->v = &uv->u.value;  /* now current value lives here */
       luaC_upvalbarrier(L, uv);
     }
   }
+  return status;
 }
 
 

src/llex.c

@@ -40,7 +40,7 @@
 static const char *const luaX_tokens [] = {
     "and", "break", "do", "else", "elseif",
     "end", "false", "for", "function", "goto", "if",
-    "in", "local", "nil", "not", "or", "repeat",
+    "in", "local", "defer", "nil", "not", "or", "repeat",
     "return", "then", "true", "until", "while",
     "//", "..", "...", "==", ">=", "<=", "~=",
     "<<", ">>", "::", "<eof>",

src/lopcodes.c

@@ -163,6 +163,7 @@ LUAI_DDEF const char *const luaP_opnames[NUM_OPCODES+1] = {
   "SELF_SK",    /* _SK*/ /* A B C	R(A+1) := R(B); R(A) := R(B)[RK(C)]		*/
   "SETFIELD", /*_SK */ /*	A B C	R(A)[RK(B)] := RK(C), string key  */
   "GETTABUP_SK",
+  "DEFER",
    NULL
 };
 
@@ -304,6 +305,9 @@ LUAI_DDEF const lu_byte luaP_opmodes[NUM_OPCODES] = {
  ,opmode(0, 1, OpArgR, OpArgK, iABC)		/* OP_RAVI_SELF_SK */
  ,opmode(0, 0, OpArgK, OpArgK, iABC)		/* OP_RAVI_SETFIELD */
  ,opmode(0, 1, OpArgU, OpArgK, iABC)		/* OP_RAVI_GETTABUP_SK */
+
+ ,opmode(0, 1, OpArgN, OpArgN, iABC)		/* OP_RAVI_DEFER */
+
 };
 
 

src/lparser.c

@@ -2177,11 +2177,18 @@ static void ifstat (LexState *ls, int line) {
 }
 
 /* parse a local function statement - called from statement() */
-static void localfunc (LexState *ls) {
+static void localfunc (LexState *ls, int defer) {
   expdesc b = {.ravi_type = RAVI_TANY, .pc = -1};
   FuncState *fs = ls->fs;
-  /* RAVI change - add type */
-  new_localvar(ls, str_checkname(ls), RAVI_TFUNCTION, NULL);  /* new local variable */
+  if (defer) {
+    static const char funcname[] = "(deferred function)";
+    new_localvar(ls, luaX_newstring(ls, funcname, sizeof funcname-1), RAVI_TFUNCTION, NULL);  /* new local variable */
+    luaK_codeABC(fs, OP_RAVI_DEFER, fs->nactvar, 0, 0);
+    markupval(fs, fs->nactvar);
+  } else {
+    /* RAVI change - add type */
+    new_localvar(ls, str_checkname(ls), RAVI_TFUNCTION, NULL);  /* new local variable */
+  }
   adjustlocalvars(ls, 1);  /* enter its scope */
   body(ls, &b, 0, ls->linenumber);  /* function created in next register */
   /* debug information will only see the variable after this point! */
@@ -2339,11 +2346,17 @@ static void statement (LexState *ls) {
     case TK_LOCAL: {  /* stat -> localstat */
       luaX_next(ls);  /* skip LOCAL */
       if (testnext(ls, TK_FUNCTION))  /* local function? */
-        localfunc(ls);
+        localfunc(ls, 0);
       else
         localstat(ls);
       break;
     }
+    case TK_DEFER: {  /* stat -> deferstat */
+      luaX_next(ls);  /* skip LOCAL */
+      checknext(ls, TK_FUNCTION);
+      localfunc(ls, 1);
+      break;
+    }
     case TK_DBCOLON: {  /* stat -> label */
       luaX_next(ls);  /* skip double colon */
       labelstat(ls, str_checkname(ls), line);

src/lstate.c

@@ -270,7 +270,7 @@ void *ravi_alloc_f(void *msp, void *ptr, size_t osize, size_t nsize)
 
 static void close_state (lua_State *L) {
   global_State *g = G(L);
-  luaF_close(L, L->stack);  /* close all upvalues for this thread */
+  luaF_close(L, L->stack, -1);  /* close all upvalues for this thread */
   luaC_freeallobjects(L);  /* collect all objects */
   if (g->version)  /* closing a fully built state? */
     luai_userstateclose(L);
@@ -317,7 +317,7 @@ LUA_API lua_State *lua_newthread (lua_State *L) {
 
 void luaE_freethread (lua_State *L, lua_State *L1) {
   LX *l = fromstate(L1);
-  luaF_close(L1, L1->stack);  /* close all upvalues for this thread */
+  luaF_close(L1, L1->stack, -1);  /* close all upvalues for this thread */
   lua_assert(L1->openupval == NULL);
   luai_userstatefree(L, L1);
   freestack(L1);

src/lvm.c

@@ -1027,7 +1027,7 @@ void luaV_finishOp (lua_State *L) {
 */
 #define dojump(ci,i,e) \
   { int a = GETARG_A(i); \
-    if (a != 0) luaF_close(L, ci->u.l.base + a - 1); \
+    if (a != 0) luaF_close(L, ci->u.l.base + a - 1, LUA_OK); \
     pc += GETARG_sBx(i) + e; updatemask(L); }
 
 /* for test instructions, execute the jump instruction that follows it */
@@ -1269,7 +1269,8 @@ int luaV_execute (lua_State *L) {
     &&vmlabel(OP_RAVI_GETFIELD),
     &&vmlabel(OP_RAVI_SELF_SK),
     &&vmlabel(OP_RAVI_SETFIELD),
-    &&vmlabel(OP_RAVI_GETTABUP_SK)
+    &&vmlabel(OP_RAVI_GETTABUP_SK),
+    &&vmlabel(OP_RAVI_DEFER),
   };
 #endif
 
@@ -1720,7 +1721,7 @@ int luaV_execute (lua_State *L) {
           StkId lim = nci->u.l.base + getproto(nfunc)->numparams;
           int aux;
           /* close all upvalues from previous call */
-          if (cl->p->sizep > 0) luaF_close(L, oci->u.l.base);
+          if (cl->p->sizep > 0) luaF_close(L, oci->u.l.base, LUA_OK);
           /* move new frame into old one */
           for (aux = 0; nfunc + aux < lim; aux++)
             setobjs2s(L, ofunc + aux, nfunc + aux);
@@ -1737,7 +1738,7 @@ int luaV_execute (lua_State *L) {
       }
       vmcase(OP_RETURN) {
         int b = GETARG_B(i);
-        if (cl->p->sizep > 0) luaF_close(L, base);
+        if (cl->p->sizep > 0) luaF_close(L, base, LUA_OK);
         savepc(L);
         int nres = (b != 0 ? b - 1 : cast_int(L->top - ra));
         b = luaD_poscall(L, ci, ra, nres);
@@ -2462,6 +2463,12 @@ int luaV_execute (lua_State *L) {
         }
         vmbreak;
       }
+      vmcase(OP_RAVI_DEFER) {
+        UpVal *up = luaF_findupval(L, ra); /* create new upvalue */
+        up->flags = 1;  /* mark it as deferred */
+        setnilvalue(ra);  /* initialize it with nil */
+        vmbreak;
+      }
     }
   }
 }

src/ravi_jitshared.c

@@ -65,6 +65,7 @@ static const char Lua_header[] = ""
 "#define LUA_TFUNCTION		6\n"
 "#define LUA_TUSERDATA		7\n"
 "#define LUA_TTHREAD		8\n"
+"#define LUA_OK  0\n"
 "typedef enum {TM_INDEX,TM_NEWINDEX,TM_GC,\n"
 "	TM_MODE,TM_LEN,TM_EQ,TM_ADD,TM_SUB,TM_MUL,\n"
 "	TM_MOD,TM_POW,TM_DIV,TM_IDIV,TM_BAND,TM_BOR,\n"
@@ -515,7 +516,8 @@ static const char Lua_header[] = ""
 "};\n"
 "struct UpVal {\n"
 "	TValue *v;\n"
-"	lu_mem refcount;\n"
+"       unsigned int refcount;\n"
+"       unsigned int flags;\n"
 "	union {\n"
 "		struct {\n"
 "			UpVal *next;\n"
@@ -544,7 +546,7 @@ static const char Lua_header[] = ""
 "  (ttisinteger(o) ? (*(i) = ivalue(o), 1) : luaV_tointeger(o,i,LUA_FLOORN2I))\n"
 "extern int luaV_tonumber_(const TValue *obj, lua_Number *n);\n"
 "extern int luaV_tointeger(const TValue *obj, lua_Integer *p, int mode);\n"
-"extern void luaF_close (lua_State *L, StkId level);\n"
+"extern int luaF_close (lua_State *L, StkId level, int status);\n"
 "extern int luaD_poscall (lua_State *L, CallInfo *ci, StkId firstResult, int nres);\n"
 "extern int luaV_equalobj(lua_State *L, const TValue *t1, const TValue *t2);\n"
 "extern int luaV_lessthan(lua_State *L, const TValue *l, const TValue *r);\n"
@@ -1010,7 +1012,7 @@ static void emit_comparison(struct function *fn, int A, int B, int C, int j, int
   membuff_add_fstring(&fn->body, "if (result == %d) {\n", A);
   if (jA > 0) {
     membuff_add_fstring(&fn->body, " ra = R(%d);\n", jA - 1);
-    membuff_add_string(&fn->body, " luaF_close(L, ra);\n");
+    membuff_add_string(&fn->body, " luaF_close(L, ra, LUA_OK);\n");
   }
   membuff_add_fstring(&fn->body, "  goto Lbc_%d;\n", j);
   membuff_add_string(&fn->body, "}\n");
@@ -1043,7 +1045,7 @@ static void emit_op_loadk(struct function *fn, int A, int Bx, int pc) {
 static void emit_op_return(struct function *fn, int A, int B, int pc) {
   (void)pc;
   emit_reg(fn, "ra", A);
-  membuff_add_string(&fn->body, "if (cl->p->sizep > 0) luaF_close(L, base);\n");
+  membuff_add_string(&fn->body, "if (cl->p->sizep > 0) luaF_close(L, base, LUA_OK);\n");
   membuff_add_fstring(&fn->body, "result = (%d != 0 ? %d - 1 : cast_int(L->top - ra));\n", B, B);
   membuff_add_string(&fn->body, "return luaD_poscall(L, ci, ra, result);\n");
 }
@@ -1066,7 +1068,7 @@ static void emit_op_jmp(struct function *fn, int A, int sBx, int pc) {
   (void)pc;
   if (A > 0) {
     membuff_add_fstring(&fn->body, "ra = R(%d);\n", A - 1);
-    membuff_add_string(&fn->body, "luaF_close(L, ra);\n");
+    membuff_add_string(&fn->body, "luaF_close(L, ra, LUA_OK);\n");
   }
   membuff_add_fstring(&fn->body, "goto Lbc_%d;\n", sBx);
 }
@@ -1090,7 +1092,7 @@ static void emit_op_test(struct function *fn, int A, int B, int C, int j, int jA
   membuff_add_fstring(&fn->body, "if (!result) {\n", A);
   if (jA > 0) {
     membuff_add_fstring(&fn->body, " ra = R(%d);\n", jA - 1);
-    membuff_add_string(&fn->body, " luaF_close(L, ra);\n");
+    membuff_add_string(&fn->body, " luaF_close(L, ra, LUA_OK);\n");
   }
   membuff_add_fstring(&fn->body, "  goto Lbc_%d;\n", j);
   membuff_add_string(&fn->body, " }\n");
@@ -1108,7 +1110,7 @@ static void emit_op_testset(struct function *fn, int A, int B, int C, int j, int
   membuff_add_string(&fn->body, "  setobjs2s(L, ra, rb);");
   if (jA > 0) {
     membuff_add_fstring(&fn->body, " ra = R(%d);\n", jA - 1);
-    membuff_add_string(&fn->body, " luaF_close(L, ra);\n");
+    membuff_add_string(&fn->body, " luaF_close(L, ra, LUA_OK);\n");
   }
   membuff_add_fstring(&fn->body, "  goto Lbc_%d;\n", j);
   membuff_add_string(&fn->body, " }\n");

src/ravi_llvmcall.cpp

@@ -52,7 +52,7 @@ void RaviCodeGenerator::emit_JMP(RaviFunctionDef *def, int A, int sBx, int pc) {
     // base + a - 1
     llvm::Value *val = emit_gep_register(def, A - 1);
     // Call luaF_close
-    CreateCall2(def->builder, def->luaF_closeF, def->L, val);
+    CreateCall3(def->builder, def->luaF_closeF, def->L, val, def->types->kInt[LUA_OK]);
   }
 
   // Do the actual jump