1/*
2** Metamethod handling.
3** Copyright (C) 2005-2021 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_buf.h"
16#include "lj_str.h"
17#include "lj_tab.h"
18#include "lj_meta.h"
19#include "lj_frame.h"
20#include "lj_bc.h"
21#include "lj_vm.h"
22#include "lj_strscan.h"
23#include "lj_strfmt.h"
24#include "lj_lib.h"
25
26/* -- Metamethod handling ------------------------------------------------- */
27
28/* String interning of metamethod names for fast indexing. */
29void lj_meta_init(lua_State *L)
30{
31#define MMNAME(name) "__" #name
32 const char *metanames = MMDEF(MMNAME);
33#undef MMNAME
34 global_State *g = G(L);
35 const char *p, *q;
36 uint32_t mm;
37 for (mm = 0, p = metanames; *p; mm++, p = q) {
38 GCstr *s;
39 for (q = p+2; *q && *q != '_'; q++) ;
40 s = lj_str_new(L, p, (size_t)(q-p));
41 /* NOBARRIER: g->gcroot[] is a GC root. */
42 setgcref(g->gcroot[GCROOT_MMNAME+mm], obj2gco(s));
43 }
44}
45
46/* Negative caching of a few fast metamethods. See the lj_meta_fast() macro. */
47cTValue *lj_meta_cache(GCtab *mt, MMS mm, GCstr *name)
48{
49 cTValue *mo = lj_tab_getstr(mt, name);
50 lj_assertX(mm <= MM_FAST, "bad metamethod %d", mm);
51 if (!mo || tvisnil(mo)) { /* No metamethod? */
52 mt->nomm |= (uint8_t)(1u<<mm); /* Set negative cache flag. */
53 return NULL;
54 }
55 return mo;
56}
57
58/* Lookup metamethod for object. */
59cTValue *lj_meta_lookup(lua_State *L, cTValue *o, MMS mm)
60{
61 GCtab *mt;
62 if (tvistab(o))
63 mt = tabref(tabV(o)->metatable);
64 else if (tvisudata(o))
65 mt = tabref(udataV(o)->metatable);
66 else
67 mt = tabref(basemt_obj(G(L), o));
68 if (mt) {
69 cTValue *mo = lj_tab_getstr(mt, mmname_str(G(L), mm));
70 if (mo)
71 return mo;
72 }
73 return niltv(L);
74}
75
76#if LJ_HASFFI
77/* Tailcall from C function. */
78int lj_meta_tailcall(lua_State *L, cTValue *tv)
79{
80 TValue *base = L->base;
81 TValue *top = L->top;
82 const BCIns *pc = frame_pc(base-1); /* Preserve old PC from frame. */
83 copyTV(L, base-1-LJ_FR2, tv); /* Replace frame with new object. */
84 if (LJ_FR2)
85 (top++)->u64 = LJ_CONT_TAILCALL;
86 else
87 top->u32.lo = LJ_CONT_TAILCALL;
88 setframe_pc(top++, pc);
89 setframe_gc(top, obj2gco(L), LJ_TTHREAD); /* Dummy frame object. */
90 if (LJ_FR2) top++;
91 setframe_ftsz(top, ((char *)(top+1) - (char *)base) + FRAME_CONT);
92 L->base = L->top = top+1;
93 /*
94 ** before: [old_mo|PC] [... ...]
95 ** ^base ^top
96 ** after: [new_mo|itype] [... ...] [NULL|PC] [dummy|delta]
97 ** ^base/top
98 ** tailcall: [new_mo|PC] [... ...]
99 ** ^base ^top
100 */
101 return 0;
102}
103#endif
104
105/* Setup call to metamethod to be run by Assembler VM. */
106static TValue *mmcall(lua_State *L, ASMFunction cont, cTValue *mo,
107 cTValue *a, cTValue *b)
108{
109 /*
110 ** |-- framesize -> top top+1 top+2 top+3
111 ** before: [func slots ...]
112 ** mm setup: [func slots ...] [cont|?] [mo|tmtype] [a] [b]
113 ** in asm: [func slots ...] [cont|PC] [mo|delta] [a] [b]
114 ** ^-- func base ^-- mm base
115 ** after mm: [func slots ...] [result]
116 ** ^-- copy to base[PC_RA] --/ for lj_cont_ra
117 ** istruecond + branch for lj_cont_cond*
118 ** ignore for lj_cont_nop
119 ** next PC: [func slots ...]
120 */
121 TValue *top = L->top;
122 if (curr_funcisL(L)) top = curr_topL(L);
123 setcont(top++, cont); /* Assembler VM stores PC in upper word or FR2. */
124 if (LJ_FR2) setnilV(top++);
125 copyTV(L, top++, mo); /* Store metamethod and two arguments. */
126 if (LJ_FR2) setnilV(top++);
127 copyTV(L, top, a);
128 copyTV(L, top+1, b);
129 return top; /* Return new base. */
130}
131
132/* -- C helpers for some instructions, called from assembler VM ----------- */
133
134/* Helper for TGET*. __index chain and metamethod. */
135cTValue *lj_meta_tget(lua_State *L, cTValue *o, cTValue *k)
136{
137 int loop;
138 for (loop = 0; loop < LJ_MAX_IDXCHAIN; loop++) {
139 cTValue *mo;
140 if (LJ_LIKELY(tvistab(o))) {
141 GCtab *t = tabV(o);
142 cTValue *tv = lj_tab_get(L, t, k);
143 if (!tvisnil(tv) ||
144 !(mo = lj_meta_fast(L, tabref(t->metatable), MM_index)))
145 return tv;
146 } else if (tvisnil(mo = lj_meta_lookup(L, o, MM_index))) {
147 lj_err_optype(L, o, LJ_ERR_OPINDEX);
148 return NULL; /* unreachable */
149 }
150 if (tvisfunc(mo)) {
151 L->top = mmcall(L, lj_cont_ra, mo, o, k);
152 return NULL; /* Trigger metamethod call. */
153 }
154 o = mo;
155 }
156 lj_err_msg(L, LJ_ERR_GETLOOP);
157 return NULL; /* unreachable */
158}
159
160/* Helper for TSET*. __newindex chain and metamethod. */
161TValue *lj_meta_tset(lua_State *L, cTValue *o, cTValue *k)
162{
163 TValue tmp;
164 int loop;
165 for (loop = 0; loop < LJ_MAX_IDXCHAIN; loop++) {
166 cTValue *mo;
167 if (LJ_LIKELY(tvistab(o))) {
168 GCtab *t = tabV(o);
169 cTValue *tv = lj_tab_get(L, t, k);
170 if (LJ_LIKELY(!tvisnil(tv))) {
171 t->nomm = 0; /* Invalidate negative metamethod cache. */
172 lj_gc_anybarriert(L, t);
173 return (TValue *)tv;
174 } else if (!(mo = lj_meta_fast(L, tabref(t->metatable), MM_newindex))) {
175 t->nomm = 0; /* Invalidate negative metamethod cache. */
176 lj_gc_anybarriert(L, t);
177 if (tv != niltv(L))
178 return (TValue *)tv;
179 if (tvisnil(k)) lj_err_msg(L, LJ_ERR_NILIDX);
180 else if (tvisint(k)) { setnumV(&tmp, (lua_Number)intV(k)); k = &tmp; }
181 else if (tvisnum(k) && tvisnan(k)) lj_err_msg(L, LJ_ERR_NANIDX);
182 return lj_tab_newkey(L, t, k);
183 }
184 } else if (tvisnil(mo = lj_meta_lookup(L, o, MM_newindex))) {
185 lj_err_optype(L, o, LJ_ERR_OPINDEX);
186 return NULL; /* unreachable */
187 }
188 if (tvisfunc(mo)) {
189 L->top = mmcall(L, lj_cont_nop, mo, o, k);
190 /* L->top+2 = v filled in by caller. */
191 return NULL; /* Trigger metamethod call. */
192 }
193 copyTV(L, &tmp, mo);
194 o = &tmp;
195 }
196 lj_err_msg(L, LJ_ERR_SETLOOP);
197 return NULL; /* unreachable */
198}
199
200static cTValue *str2num(cTValue *o, TValue *n)
201{
202 if (tvisnum(o))
203 return o;
204 else if (tvisint(o))
205 return (setnumV(n, (lua_Number)intV(o)), n);
206 else if (tvisstr(o) && lj_strscan_num(strV(o), n))
207 return n;
208 else
209 return NULL;
210}
211
212/* Helper for arithmetic instructions. Coercion, metamethod. */
213TValue *lj_meta_arith(lua_State *L, TValue *ra, cTValue *rb, cTValue *rc,
214 BCReg op)
215{
216 MMS mm = bcmode_mm(op);
217 TValue tempb, tempc;
218 cTValue *b, *c;
219 if ((b = str2num(rb, &tempb)) != NULL &&
220 (c = str2num(rc, &tempc)) != NULL) { /* Try coercion first. */
221 setnumV(ra, lj_vm_foldarith(numV(b), numV(c), (int)mm-MM_add));
222 return NULL;
223 } else {
224 cTValue *mo = lj_meta_lookup(L, rb, mm);
225 if (tvisnil(mo)) {
226 mo = lj_meta_lookup(L, rc, mm);
227 if (tvisnil(mo)) {
228 if (str2num(rb, &tempb) == NULL) rc = rb;
229 lj_err_optype(L, rc, LJ_ERR_OPARITH);
230 return NULL; /* unreachable */
231 }
232 }
233 return mmcall(L, lj_cont_ra, mo, rb, rc);
234 }
235}
236
237/* Helper for CAT. Coercion, iterative concat, __concat metamethod. */
238TValue *lj_meta_cat(lua_State *L, TValue *top, int left)
239{
240 int fromc = 0;
241 if (left < 0) { left = -left; fromc = 1; }
242 do {
243 if (!(tvisstr(top) || tvisnumber(top)) ||
244 !(tvisstr(top-1) || tvisnumber(top-1))) {
245 cTValue *mo = lj_meta_lookup(L, top-1, MM_concat);
246 if (tvisnil(mo)) {
247 mo = lj_meta_lookup(L, top, MM_concat);
248 if (tvisnil(mo)) {
249 if (tvisstr(top-1) || tvisnumber(top-1)) top++;
250 lj_err_optype(L, top-1, LJ_ERR_OPCAT);
251 return NULL; /* unreachable */
252 }
253 }
254 /* One of the top two elements is not a string, call __cat metamethod:
255 **
256 ** before: [...][CAT stack .........................]
257 ** top-1 top top+1 top+2
258 ** pick two: [...][CAT stack ...] [o1] [o2]
259 ** setup mm: [...][CAT stack ...] [cont|?] [mo|tmtype] [o1] [o2]
260 ** in asm: [...][CAT stack ...] [cont|PC] [mo|delta] [o1] [o2]
261 ** ^-- func base ^-- mm base
262 ** after mm: [...][CAT stack ...] <--push-- [result]
263 ** next step: [...][CAT stack .............]
264 */
265 copyTV(L, top+2*LJ_FR2+2, top); /* Carefully ordered stack copies! */
266 copyTV(L, top+2*LJ_FR2+1, top-1);
267 copyTV(L, top+LJ_FR2, mo);
268 setcont(top-1, lj_cont_cat);
269 if (LJ_FR2) { setnilV(top); setnilV(top+2); top += 2; }
270 return top+1; /* Trigger metamethod call. */
271 } else {
272 /* Pick as many strings as possible from the top and concatenate them:
273 **
274 ** before: [...][CAT stack ...........................]
275 ** pick str: [...][CAT stack ...] [...... strings ......]
276 ** concat: [...][CAT stack ...] [result]
277 ** next step: [...][CAT stack ............]
278 */
279 TValue *e, *o = top;
280 uint64_t tlen = tvisstr(o) ? strV(o)->len : STRFMT_MAXBUF_NUM;
281 SBuf *sb;
282 do {
283 o--; tlen += tvisstr(o) ? strV(o)->len : STRFMT_MAXBUF_NUM;
284 } while (--left > 0 && (tvisstr(o-1) || tvisnumber(o-1)));
285 if (tlen >= LJ_MAX_STR) lj_err_msg(L, LJ_ERR_STROV);
286 sb = lj_buf_tmp_(L);
287 lj_buf_more(sb, (MSize)tlen);
288 for (e = top, top = o; o <= e; o++) {
289 if (tvisstr(o)) {
290 GCstr *s = strV(o);
291 MSize len = s->len;
292 lj_buf_putmem(sb, strdata(s), len);
293 } else if (tvisint(o)) {
294 lj_strfmt_putint(sb, intV(o));
295 } else {
296 lj_strfmt_putfnum(sb, STRFMT_G14, numV(o));
297 }
298 }
299 setstrV(L, top, lj_buf_str(L, sb));
300 }
301 } while (left >= 1);
302 if (LJ_UNLIKELY(G(L)->gc.total >= G(L)->gc.threshold)) {
303 if (!fromc) L->top = curr_topL(L);
304 lj_gc_step(L);
305 }
306 return NULL;
307}
308
309/* Helper for LEN. __len metamethod. */
310TValue * LJ_FASTCALL lj_meta_len(lua_State *L, cTValue *o)
311{
312 cTValue *mo = lj_meta_lookup(L, o, MM_len);
313 if (tvisnil(mo)) {
314 if (LJ_52 && tvistab(o))
315 tabref(tabV(o)->metatable)->nomm |= (uint8_t)(1u<<MM_len);
316 else
317 lj_err_optype(L, o, LJ_ERR_OPLEN);
318 return NULL;
319 }
320 return mmcall(L, lj_cont_ra, mo, o, LJ_52 ? o : niltv(L));
321}
322
323/* Helper for equality comparisons. __eq metamethod. */
324TValue *lj_meta_equal(lua_State *L, GCobj *o1, GCobj *o2, int ne)
325{
326 /* Field metatable must be at same offset for GCtab and GCudata! */
327 cTValue *mo = lj_meta_fast(L, tabref(o1->gch.metatable), MM_eq);
328 if (mo) {
329 TValue *top;
330 uint32_t it;
331 if (tabref(o1->gch.metatable) != tabref(o2->gch.metatable)) {
332 cTValue *mo2 = lj_meta_fast(L, tabref(o2->gch.metatable), MM_eq);
333 if (mo2 == NULL || !lj_obj_equal(mo, mo2))
334 return (TValue *)(intptr_t)ne;
335 }
336 top = curr_top(L);
337 setcont(top++, ne ? lj_cont_condf : lj_cont_condt);
338 if (LJ_FR2) setnilV(top++);
339 copyTV(L, top++, mo);
340 if (LJ_FR2) setnilV(top++);
341 it = ~(uint32_t)o1->gch.gct;
342 setgcV(L, top, o1, it);
343 setgcV(L, top+1, o2, it);
344 return top; /* Trigger metamethod call. */
345 }
346 return (TValue *)(intptr_t)ne;
347}
348
349#if LJ_HASFFI
350TValue * LJ_FASTCALL lj_meta_equal_cd(lua_State *L, BCIns ins)
351{
352 ASMFunction cont = (bc_op(ins) & 1) ? lj_cont_condf : lj_cont_condt;
353 int op = (int)bc_op(ins) & ~1;
354 TValue tv;
355 cTValue *mo, *o2, *o1 = &L->base[bc_a(ins)];
356 cTValue *o1mm = o1;
357 if (op == BC_ISEQV) {
358 o2 = &L->base[bc_d(ins)];
359 if (!tviscdata(o1mm)) o1mm = o2;
360 } else if (op == BC_ISEQS) {
361 setstrV(L, &tv, gco2str(proto_kgc(curr_proto(L), ~(ptrdiff_t)bc_d(ins))));
362 o2 = &tv;
363 } else if (op == BC_ISEQN) {
364 o2 = &mref(curr_proto(L)->k, cTValue)[bc_d(ins)];
365 } else {
366 lj_assertL(op == BC_ISEQP, "bad bytecode op %d", op);
367 setpriV(&tv, ~bc_d(ins));
368 o2 = &tv;
369 }
370 mo = lj_meta_lookup(L, o1mm, MM_eq);
371 if (LJ_LIKELY(!tvisnil(mo)))
372 return mmcall(L, cont, mo, o1, o2);
373 else
374 return (TValue *)(intptr_t)(bc_op(ins) & 1);
375}
376#endif
377
378/* Helper for ordered comparisons. String compare, __lt/__le metamethods. */
379TValue *lj_meta_comp(lua_State *L, cTValue *o1, cTValue *o2, int op)
380{
381 if (LJ_HASFFI && (tviscdata(o1) || tviscdata(o2))) {
382 ASMFunction cont = (op & 1) ? lj_cont_condf : lj_cont_condt;
383 MMS mm = (op & 2) ? MM_le : MM_lt;
384 cTValue *mo = lj_meta_lookup(L, tviscdata(o1) ? o1 : o2, mm);
385 if (LJ_UNLIKELY(tvisnil(mo))) goto err;
386 return mmcall(L, cont, mo, o1, o2);
387 } else if (LJ_52 || itype(o1) == itype(o2)) {
388 /* Never called with two numbers. */
389 if (tvisstr(o1) && tvisstr(o2)) {
390 int32_t res = lj_str_cmp(strV(o1), strV(o2));
391 return (TValue *)(intptr_t)(((op&2) ? res <= 0 : res < 0) ^ (op&1));
392 } else {
393 trymt:
394 while (1) {
395 ASMFunction cont = (op & 1) ? lj_cont_condf : lj_cont_condt;
396 MMS mm = (op & 2) ? MM_le : MM_lt;
397 cTValue *mo = lj_meta_lookup(L, o1, mm);
398#if LJ_52
399 if (tvisnil(mo) && tvisnil((mo = lj_meta_lookup(L, o2, mm))))
400#else
401 cTValue *mo2 = lj_meta_lookup(L, o2, mm);
402 if (tvisnil(mo) || !lj_obj_equal(mo, mo2))
403#endif
404 {
405 if (op & 2) { /* MM_le not found: retry with MM_lt. */
406 cTValue *ot = o1; o1 = o2; o2 = ot; /* Swap operands. */
407 op ^= 3; /* Use LT and flip condition. */
408 continue;
409 }
410 goto err;
411 }
412 return mmcall(L, cont, mo, o1, o2);
413 }
414 }
415 } else if (tvisbool(o1) && tvisbool(o2)) {
416 goto trymt;
417 } else {
418 err:
419 lj_err_comp(L, o1, o2);
420 return NULL;
421 }
422}
423
424/* Helper for ISTYPE and ISNUM. Implicit coercion or error. */
425void lj_meta_istype(lua_State *L, BCReg ra, BCReg tp)
426{
427 L->top = curr_topL(L);
428 ra++; tp--;
429 lj_assertL(LJ_DUALNUM || tp != ~LJ_TNUMX, "bad type for ISTYPE");
430 if (LJ_DUALNUM && tp == ~LJ_TNUMX) lj_lib_checkint(L, ra);
431 else if (tp == ~LJ_TNUMX+1) lj_lib_checknum(L, ra);
432 else if (tp == ~LJ_TSTR) lj_lib_checkstr(L, ra);
433 else lj_err_argtype(L, ra, lj_obj_itypename[tp]);
434}
435
436/* Helper for calls. __call metamethod. */
437void lj_meta_call(lua_State *L, TValue *func, TValue *top)
438{
439 cTValue *mo = lj_meta_lookup(L, func, MM_call);
440 TValue *p;
441 if (!tvisfunc(mo))
442 lj_err_optype_call(L, func);
443 for (p = top; p > func+2*LJ_FR2; p--) copyTV(L, p, p-1);
444 if (LJ_FR2) copyTV(L, func+2, func);
445 copyTV(L, func, mo);
446}
447
448/* Helper for FORI. Coercion. */
449void LJ_FASTCALL lj_meta_for(lua_State *L, TValue *o)
450{
451 if (!lj_strscan_numberobj(o)) lj_err_msg(L, LJ_ERR_FORINIT);
452 if (!lj_strscan_numberobj(o+1)) lj_err_msg(L, LJ_ERR_FORLIM);
453 if (!lj_strscan_numberobj(o+2)) lj_err_msg(L, LJ_ERR_FORSTEP);
454 if (LJ_DUALNUM) {
455 /* Ensure all slots are integers or all slots are numbers. */
456 int32_t k[3];
457 int nint = 0;
458 ptrdiff_t i;
459 for (i = 0; i <= 2; i++) {
460 if (tvisint(o+i)) {
461 k[i] = intV(o+i); nint++;
462 } else {
463 k[i] = lj_num2int(numV(o+i)); nint += ((lua_Number)k[i] == numV(o+i));
464 }
465 }
466 if (nint == 3) { /* Narrow to integers. */
467 setintV(o, k[0]);
468 setintV(o+1, k[1]);
469 setintV(o+2, k[2]);
470 } else if (nint != 0) { /* Widen to numbers. */
471 if (tvisint(o)) setnumV(o, (lua_Number)intV(o));
472 if (tvisint(o+1)) setnumV(o+1, (lua_Number)intV(o+1));
473 if (tvisint(o+2)) setnumV(o+2, (lua_Number)intV(o+2));
474 }
475 }
476}
477
478