1/*
2** Metamethod handling.
3** Copyright (C) 2005-2014 Mike Pall. See Copyright Notice in luajit.h
4**
5** Portions taken verbatim or adapted from the Lua interpreter.
6** Copyright (C) 1994-2008 Lua.org, PUC-Rio. See Copyright Notice in lua.h
7*/
8
9#define lj_meta_c
10#define LUA_CORE
11
12#include "lj_obj.h"
13#include "lj_gc.h"
14#include "lj_err.h"
15#include "lj_str.h"
16#include "lj_tab.h"
17#include "lj_meta.h"
18#include "lj_frame.h"
19#include "lj_bc.h"
20#include "lj_vm.h"
21#include "lj_strscan.h"
22
23/* -- Metamethod handling ------------------------------------------------- */
24
25/* String interning of metamethod names for fast indexing. */
26void lj_meta_init(lua_State *L)
27{
28#define MMNAME(name) "__" #name
29 const char *metanames = MMDEF(MMNAME);
30#undef MMNAME
31 global_State *g = G(L);
32 const char *p, *q;
33 uint32_t mm;
34 for (mm = 0, p = metanames; *p; mm++, p = q) {
35 GCstr *s;
36 for (q = p+2; *q && *q != '_'; q++) ;
37 s = lj_str_new(L, p, (size_t)(q-p));
38 /* NOBARRIER: g->gcroot[] is a GC root. */
39 setgcref(g->gcroot[GCROOT_MMNAME+mm], obj2gco(s));
40 }
41}
42
43/* Negative caching of a few fast metamethods. See the lj_meta_fast() macro. */
44cTValue *lj_meta_cache(GCtab *mt, MMS mm, GCstr *name)
45{
46 cTValue *mo = lj_tab_getstr(mt, name);
47 lua_assert(mm <= MM_FAST);
48 if (!mo || tvisnil(mo)) { /* No metamethod? */
49 mt->nomm |= (uint8_t)(1u<<mm); /* Set negative cache flag. */
50 return NULL;
51 }
52 return mo;
53}
54
55/* Lookup metamethod for object. */
56cTValue *lj_meta_lookup(lua_State *L, cTValue *o, MMS mm)
57{
58 GCtab *mt;
59 if (tvistab(o))
60 mt = tabref(tabV(o)->metatable);
61 else if (tvisudata(o))
62 mt = tabref(udataV(o)->metatable);
63 else
64 mt = tabref(basemt_obj(G(L), o));
65 if (mt) {
66 cTValue *mo = lj_tab_getstr(mt, mmname_str(G(L), mm));
67 if (mo)
68 return mo;
69 }
70 return niltv(L);
71}
72
73#if LJ_HASFFI
74/* Tailcall from C function. */
75int lj_meta_tailcall(lua_State *L, cTValue *tv)
76{
77 TValue *base = L->base;
78 TValue *top = L->top;
79 const BCIns *pc = frame_pc(base-1); /* Preserve old PC from frame. */
80 copyTV(L, base-1, tv); /* Replace frame with new object. */
81 top->u32.lo = LJ_CONT_TAILCALL;
82 setframe_pc(top, pc);
83 setframe_gc(top+1, obj2gco(L)); /* Dummy frame object. */
84 setframe_ftsz(top+1, (int)((char *)(top+2) - (char *)base) + FRAME_CONT);
85 L->base = L->top = top+2;
86 /*
87 ** before: [old_mo|PC] [... ...]
88 ** ^base ^top
89 ** after: [new_mo|itype] [... ...] [NULL|PC] [dummy|delta]
90 ** ^base/top
91 ** tailcall: [new_mo|PC] [... ...]
92 ** ^base ^top
93 */
94 return 0;
95}
96#endif
97
98/* Setup call to metamethod to be run by Assembler VM. */
99static TValue *mmcall(lua_State *L, ASMFunction cont, cTValue *mo,
100 cTValue *a, cTValue *b)
101{
102 /*
103 ** |-- framesize -> top top+1 top+2 top+3
104 ** before: [func slots ...]
105 ** mm setup: [func slots ...] [cont|?] [mo|tmtype] [a] [b]
106 ** in asm: [func slots ...] [cont|PC] [mo|delta] [a] [b]
107 ** ^-- func base ^-- mm base
108 ** after mm: [func slots ...] [result]
109 ** ^-- copy to base[PC_RA] --/ for lj_cont_ra
110 ** istruecond + branch for lj_cont_cond*
111 ** ignore for lj_cont_nop
112 ** next PC: [func slots ...]
113 */
114 TValue *top = L->top;
115 if (curr_funcisL(L)) top = curr_topL(L);
116 setcont(top, cont); /* Assembler VM stores PC in upper word. */
117 copyTV(L, top+1, mo); /* Store metamethod and two arguments. */
118 copyTV(L, top+2, a);
119 copyTV(L, top+3, b);
120 return top+2; /* Return new base. */
121}
122
123/* -- C helpers for some instructions, called from assembler VM ----------- */
124
125/* Helper for TGET*. __index chain and metamethod. */
126cTValue *lj_meta_tget(lua_State *L, cTValue *o, cTValue *k)
127{
128 int loop;
129 for (loop = 0; loop < LJ_MAX_IDXCHAIN; loop++) {
130 cTValue *mo;
131 if (LJ_LIKELY(tvistab(o))) {
132 GCtab *t = tabV(o);
133 cTValue *tv = lj_tab_get(L, t, k);
134 if (!tvisnil(tv) ||
135 !(mo = lj_meta_fast(L, tabref(t->metatable), MM_index)))
136 return tv;
137 } else if (tvisnil(mo = lj_meta_lookup(L, o, MM_index))) {
138 lj_err_optype(L, o, LJ_ERR_OPINDEX);
139 return NULL; /* unreachable */
140 }
141 if (tvisfunc(mo)) {
142 L->top = mmcall(L, lj_cont_ra, mo, o, k);
143 return NULL; /* Trigger metamethod call. */
144 }
145 o = mo;
146 }
147 lj_err_msg(L, LJ_ERR_GETLOOP);
148 return NULL; /* unreachable */
149}
150
151/* Helper for TSET*. __newindex chain and metamethod. */
152TValue *lj_meta_tset(lua_State *L, cTValue *o, cTValue *k)
153{
154 TValue tmp;
155 int loop;
156 for (loop = 0; loop < LJ_MAX_IDXCHAIN; loop++) {
157 cTValue *mo;
158 if (LJ_LIKELY(tvistab(o))) {
159 GCtab *t = tabV(o);
160 cTValue *tv = lj_tab_get(L, t, k);
161 if (LJ_LIKELY(!tvisnil(tv))) {
162 t->nomm = 0; /* Invalidate negative metamethod cache. */
163 lj_gc_anybarriert(L, t);
164 return (TValue *)tv;
165 } else if (!(mo = lj_meta_fast(L, tabref(t->metatable), MM_newindex))) {
166 t->nomm = 0; /* Invalidate negative metamethod cache. */
167 lj_gc_anybarriert(L, t);
168 if (tv != niltv(L))
169 return (TValue *)tv;
170 if (tvisnil(k)) lj_err_msg(L, LJ_ERR_NILIDX);
171 else if (tvisint(k)) { setnumV(&tmp, (lua_Number)intV(k)); k = &tmp; }
172 else if (tvisnum(k) && tvisnan(k)) lj_err_msg(L, LJ_ERR_NANIDX);
173 return lj_tab_newkey(L, t, k);
174 }
175 } else if (tvisnil(mo = lj_meta_lookup(L, o, MM_newindex))) {
176 lj_err_optype(L, o, LJ_ERR_OPINDEX);
177 return NULL; /* unreachable */
178 }
179 if (tvisfunc(mo)) {
180 L->top = mmcall(L, lj_cont_nop, mo, o, k);
181 /* L->top+2 = v filled in by caller. */
182 return NULL; /* Trigger metamethod call. */
183 }
184 copyTV(L, &tmp, mo);
185 o = &tmp;
186 }
187 lj_err_msg(L, LJ_ERR_SETLOOP);
188 return NULL; /* unreachable */
189}
190
191static cTValue *str2num(cTValue *o, TValue *n)
192{
193 if (tvisnum(o))
194 return o;
195 else if (tvisint(o))
196 return (setnumV(n, (lua_Number)intV(o)), n);
197 else if (tvisstr(o) && lj_strscan_num(strV(o), n))
198 return n;
199 else
200 return NULL;
201}
202
203/* Helper for arithmetic instructions. Coercion, metamethod. */
204TValue *lj_meta_arith(lua_State *L, TValue *ra, cTValue *rb, cTValue *rc,
205 BCReg op)
206{
207 MMS mm = bcmode_mm(op);
208 TValue tempb, tempc;
209 cTValue *b, *c;
210 if ((b = str2num(rb, &tempb)) != NULL &&
211 (c = str2num(rc, &tempc)) != NULL) { /* Try coercion first. */
212 setnumV(ra, lj_vm_foldarith(numV(b), numV(c), (int)mm-MM_add));
213 return NULL;
214 } else {
215 cTValue *mo = lj_meta_lookup(L, rb, mm);
216 if (tvisnil(mo)) {
217 mo = lj_meta_lookup(L, rc, mm);
218 if (tvisnil(mo)) {
219 if (str2num(rb, &tempb) == NULL) rc = rb;
220 lj_err_optype(L, rc, LJ_ERR_OPARITH);
221 return NULL; /* unreachable */
222 }
223 }
224 return mmcall(L, lj_cont_ra, mo, rb, rc);
225 }
226}
227
228/* In-place coercion of a number to a string. */
229static LJ_AINLINE int tostring(lua_State *L, TValue *o)
230{
231 if (tvisstr(o)) {
232 return 1;
233 } else if (tvisnumber(o)) {
234 setstrV(L, o, lj_str_fromnumber(L, o));
235 return 1;
236 } else {
237 return 0;
238 }
239}
240
241/* Helper for CAT. Coercion, iterative concat, __concat metamethod. */
242TValue *lj_meta_cat(lua_State *L, TValue *top, int left)
243{
244 int fromc = 0;
245 if (left < 0) { left = -left; fromc = 1; }
246 do {
247 int n = 1;
248 if (!(tvisstr(top-1) || tvisnumber(top-1)) || !tostring(L, top)) {
249 cTValue *mo = lj_meta_lookup(L, top-1, MM_concat);
250 if (tvisnil(mo)) {
251 mo = lj_meta_lookup(L, top, MM_concat);
252 if (tvisnil(mo)) {
253 if (tvisstr(top-1) || tvisnumber(top-1)) top++;
254 lj_err_optype(L, top-1, LJ_ERR_OPCAT);
255 return NULL; /* unreachable */
256 }
257 }
258 /* One of the top two elements is not a string, call __cat metamethod:
259 **
260 ** before: [...][CAT stack .........................]
261 ** top-1 top top+1 top+2
262 ** pick two: [...][CAT stack ...] [o1] [o2]
263 ** setup mm: [...][CAT stack ...] [cont|?] [mo|tmtype] [o1] [o2]
264 ** in asm: [...][CAT stack ...] [cont|PC] [mo|delta] [o1] [o2]
265 ** ^-- func base ^-- mm base
266 ** after mm: [...][CAT stack ...] <--push-- [result]
267 ** next step: [...][CAT stack .............]
268 */
269 copyTV(L, top+2, top); /* Careful with the order of stack copies! */
270 copyTV(L, top+1, top-1);
271 copyTV(L, top, mo);
272 setcont(top-1, lj_cont_cat);
273 return top+1; /* Trigger metamethod call. */
274 } else if (strV(top)->len == 0) { /* Shortcut. */
275 (void)tostring(L, top-1);
276 } else {
277 /* Pick as many strings as possible from the top and concatenate them:
278 **
279 ** before: [...][CAT stack ...........................]
280 ** pick str: [...][CAT stack ...] [...... strings ......]
281 ** concat: [...][CAT stack ...] [result]
282 ** next step: [...][CAT stack ............]
283 */
284 MSize tlen = strV(top)->len;
285 char *buffer;
286 int i;
287 for (n = 1; n <= left && tostring(L, top-n); n++) {
288 MSize len = strV(top-n)->len;
289 if (len >= LJ_MAX_STR - tlen)
290 lj_err_msg(L, LJ_ERR_STROV);
291 tlen += len;
292 }
293 buffer = lj_str_needbuf(L, &G(L)->tmpbuf, tlen);
294 n--;
295 tlen = 0;
296 for (i = n; i >= 0; i--) {
297 MSize len = strV(top-i)->len;
298 memcpy(buffer + tlen, strVdata(top-i), len);
299 tlen += len;
300 }
301 setstrV(L, top-n, lj_str_new(L, buffer, tlen));
302 }
303 left -= n;
304 top -= n;
305 } while (left >= 1);
306 if (LJ_UNLIKELY(G(L)->gc.total >= G(L)->gc.threshold)) {
307 if (!fromc) L->top = curr_topL(L);
308 lj_gc_step(L);
309 }
310 return NULL;
311}
312
313/* Helper for LEN. __len metamethod. */
314TValue * LJ_FASTCALL lj_meta_len(lua_State *L, cTValue *o)
315{
316 cTValue *mo = lj_meta_lookup(L, o, MM_len);
317 if (tvisnil(mo)) {
318 if (LJ_52 && tvistab(o))
319 tabref(tabV(o)->metatable)->nomm |= (uint8_t)(1u<<MM_len);
320 else
321 lj_err_optype(L, o, LJ_ERR_OPLEN);
322 return NULL;
323 }
324 return mmcall(L, lj_cont_ra, mo, o, LJ_52 ? o : niltv(L));
325}
326
327/* Helper for equality comparisons. __eq metamethod. */
328TValue *lj_meta_equal(lua_State *L, GCobj *o1, GCobj *o2, int ne)
329{
330 /* Field metatable must be at same offset for GCtab and GCudata! */
331 cTValue *mo = lj_meta_fast(L, tabref(o1->gch.metatable), MM_eq);
332 if (mo) {
333 TValue *top;
334 uint32_t it;
335 if (tabref(o1->gch.metatable) != tabref(o2->gch.metatable)) {
336 cTValue *mo2 = lj_meta_fast(L, tabref(o2->gch.metatable), MM_eq);
337 if (mo2 == NULL || !lj_obj_equal(mo, mo2))
338 return (TValue *)(intptr_t)ne;
339 }
340 top = curr_top(L);
341 setcont(top, ne ? lj_cont_condf : lj_cont_condt);
342 copyTV(L, top+1, mo);
343 it = ~(uint32_t)o1->gch.gct;
344 setgcV(L, top+2, o1, it);
345 setgcV(L, top+3, o2, it);
346 return top+2; /* Trigger metamethod call. */
347 }
348 return (TValue *)(intptr_t)ne;
349}
350
351#if LJ_HASFFI
352TValue * LJ_FASTCALL lj_meta_equal_cd(lua_State *L, BCIns ins)
353{
354 ASMFunction cont = (bc_op(ins) & 1) ? lj_cont_condf : lj_cont_condt;
355 int op = (int)bc_op(ins) & ~1;
356 TValue tv;
357 cTValue *mo, *o2, *o1 = &L->base[bc_a(ins)];
358 cTValue *o1mm = o1;
359 if (op == BC_ISEQV) {
360 o2 = &L->base[bc_d(ins)];
361 if (!tviscdata(o1mm)) o1mm = o2;
362 } else if (op == BC_ISEQS) {
363 setstrV(L, &tv, gco2str(proto_kgc(curr_proto(L), ~(ptrdiff_t)bc_d(ins))));
364 o2 = &tv;
365 } else if (op == BC_ISEQN) {
366 o2 = &mref(curr_proto(L)->k, cTValue)[bc_d(ins)];
367 } else {
368 lua_assert(op == BC_ISEQP);
369 setitype(&tv, ~bc_d(ins));
370 o2 = &tv;
371 }
372 mo = lj_meta_lookup(L, o1mm, MM_eq);
373 if (LJ_LIKELY(!tvisnil(mo)))
374 return mmcall(L, cont, mo, o1, o2);
375 else
376 return (TValue *)(intptr_t)(bc_op(ins) & 1);
377}
378#endif
379
380/* Helper for ordered comparisons. String compare, __lt/__le metamethods. */
381TValue *lj_meta_comp(lua_State *L, cTValue *o1, cTValue *o2, int op)
382{
383 if (LJ_HASFFI && (tviscdata(o1) || tviscdata(o2))) {
384 ASMFunction cont = (op & 1) ? lj_cont_condf : lj_cont_condt;
385 MMS mm = (op & 2) ? MM_le : MM_lt;
386 cTValue *mo = lj_meta_lookup(L, tviscdata(o1) ? o1 : o2, mm);
387 if (LJ_UNLIKELY(tvisnil(mo))) goto err;
388 return mmcall(L, cont, mo, o1, o2);
389 } else if (LJ_52 || itype(o1) == itype(o2)) {
390 /* Never called with two numbers. */
391 if (tvisstr(o1) && tvisstr(o2)) {
392 int32_t res = lj_str_cmp(strV(o1), strV(o2));
393 return (TValue *)(intptr_t)(((op&2) ? res <= 0 : res < 0) ^ (op&1));
394 } else {
395 trymt:
396 while (1) {
397 ASMFunction cont = (op & 1) ? lj_cont_condf : lj_cont_condt;
398 MMS mm = (op & 2) ? MM_le : MM_lt;
399 cTValue *mo = lj_meta_lookup(L, o1, mm);
400#if LJ_52
401 if (tvisnil(mo) && tvisnil((mo = lj_meta_lookup(L, o2, mm))))
402#else
403 cTValue *mo2 = lj_meta_lookup(L, o2, mm);
404 if (tvisnil(mo) || !lj_obj_equal(mo, mo2))
405#endif
406 {
407 if (op & 2) { /* MM_le not found: retry with MM_lt. */
408 cTValue *ot = o1; o1 = o2; o2 = ot; /* Swap operands. */
409 op ^= 3; /* Use LT and flip condition. */
410 continue;
411 }
412 goto err;
413 }
414 return mmcall(L, cont, mo, o1, o2);
415 }
416 }
417 } else if (tvisbool(o1) && tvisbool(o2)) {
418 goto trymt;
419 } else {
420 err:
421 lj_err_comp(L, o1, o2);
422 return NULL;
423 }
424}
425
426/* Helper for calls. __call metamethod. */
427void lj_meta_call(lua_State *L, TValue *func, TValue *top)
428{
429 cTValue *mo = lj_meta_lookup(L, func, MM_call);
430 TValue *p;
431 if (!tvisfunc(mo))
432 lj_err_optype_call(L, func);
433 for (p = top; p > func; p--) copyTV(L, p, p-1);
434 copyTV(L, func, mo);
435}
436
437/* Helper for FORI. Coercion. */
438void LJ_FASTCALL lj_meta_for(lua_State *L, TValue *o)
439{
440 if (!lj_strscan_numberobj(o)) lj_err_msg(L, LJ_ERR_FORINIT);
441 if (!lj_strscan_numberobj(o+1)) lj_err_msg(L, LJ_ERR_FORLIM);
442 if (!lj_strscan_numberobj(o+2)) lj_err_msg(L, LJ_ERR_FORSTEP);
443 if (LJ_DUALNUM) {
444 /* Ensure all slots are integers or all slots are numbers. */
445 int32_t k[3];
446 int nint = 0;
447 ptrdiff_t i;
448 for (i = 0; i <= 2; i++) {
449 if (tvisint(o+i)) {
450 k[i] = intV(o+i); nint++;
451 } else {
452 k[i] = lj_num2int(numV(o+i)); nint += ((lua_Number)k[i] == numV(o+i));
453 }
454 }
455 if (nint == 3) { /* Narrow to integers. */
456 setintV(o, k[0]);
457 setintV(o+1, k[1]);
458 setintV(o+2, k[2]);
459 } else if (nint != 0) { /* Widen to numbers. */
460 if (tvisint(o)) setnumV(o, (lua_Number)intV(o));
461 if (tvisint(o+1)) setnumV(o+1, (lua_Number)intV(o+1));
462 if (tvisint(o+2)) setnumV(o+2, (lua_Number)intV(o+2));
463 }
464 }
465}
466
467