1 /*
2 *
3 * luamm: C++ binding for lua
4 *
5 * Copyright (C) 2010 Pavel Labath et al.
6 *
7 * This program is free software: you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation, either version 3 of the License, or
10 * (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program. If not, see <http://www.gnu.org/licenses/>.
18 *
19 */
20
21 #include <config.h>
22
23 #include "luamm.hh"
24
25 namespace lua {
26 namespace {
27
28 #if LUA_VERSION_NUM >= 502
29 // These two functions were deprecated in 5.2. Limited backwards compatibility
30 // is provided by macros. We want them as real functions, because we take their
31 // addresses.
32
33 #undef lua_equal
lua_equal(lua_State * L,int index1,int index2)34 int lua_equal(lua_State *L, int index1, int index2) {
35 return lua_compare(L, index1, index2, LUA_OPEQ);
36 }
37
38 #undef lua_lessthan
lua_lessthan(lua_State * L,int index1,int index2)39 int lua_lessthan(lua_State *L, int index1, int index2) {
40 return lua_compare(L, index1, index2, LUA_OPLT);
41 }
42 #endif
43
44 // keys for storing values in lua registry
45 const char cpp_exception_metatable[] = "lua::cpp_exception_metatable";
46 const char cpp_function_metatable[] = "lua::cpp_function_metatable";
47 const char lua_exception_namespace[] = "lua::lua_exception_namespace";
48 const char this_cpp_object[] = "lua::this_cpp_object";
49
50 // converts C++ exceptions to strings, so lua can do something with them
exception_to_string(lua_State * l)51 int exception_to_string(lua_State *l) {
52 auto *ptr = static_cast<std::exception_ptr *>(lua_touserdata(l, -1));
53 assert(ptr);
54 try {
55 std::rethrow_exception(*ptr);
56 } catch (std::exception &e) { lua_pushstring(l, e.what()); } catch (...) {
57 lua_pushstring(l, typeid(*ptr).name());
58 }
59 return 1;
60 }
61
absindex(lua_State * l,int index)62 int absindex(lua_State *l, int index) {
63 return index < 0 && -index <= lua_gettop(l) ? lua_gettop(l) + 1 + index
64 : index;
65 }
66
67 // Just like getfield(), only without calling metamethods (or throwing random
68 // exceptions)
rawgetfield(lua_State * l,int index,const char * k)69 inline void rawgetfield(lua_State *l, int index, const char *k) {
70 index = absindex(l, index);
71 if (lua_checkstack(l, 1) == 0) { throw std::bad_alloc(); }
72
73 lua_pushstring(l, k);
74 lua_rawget(l, index);
75 }
76
77 // Just like setfield(), only without calling metamethods (or throwing random
78 // exceptions)
rawsetfield(lua_State * l,int index,const char * k)79 inline void rawsetfield(lua_State *l, int index, const char *k) {
80 index = absindex(l, index);
81 if (lua_checkstack(l, 2) == 0) { throw std::bad_alloc(); }
82
83 lua_pushstring(l, k);
84 lua_insert(l, -2);
85 lua_rawset(l, index);
86 }
87
closure_trampoline(lua_State * l)88 int closure_trampoline(lua_State *l) {
89 lua_checkstack(l, 2);
90 rawgetfield(l, REGISTRYINDEX, this_cpp_object);
91 assert(lua_islightuserdata(l, -1));
92 auto *L = static_cast<state *>(lua_touserdata(l, -1));
93 lua_pop(l, 1);
94
95 try {
96 auto *fn = static_cast<cpp_function *>(L->touserdata(lua_upvalueindex(1)));
97 assert(fn);
98 return (*fn)(L);
99 } catch (lua::exception &e) {
100 // rethrow lua errors as such
101 e.push_lua_error(L);
102 } catch (...) {
103 // C++ exceptions (pointers to them, actually) are stored as lua userdata
104 // and then thrown
105 L->createuserdata<std::exception_ptr>(std::current_exception());
106 L->rawgetfield(REGISTRYINDEX, cpp_exception_metatable);
107 L->setmetatable(-2);
108 }
109
110 // lua_error does longjmp(), so destructors for objects in this function will
111 // not be called
112 return lua_error(l);
113 }
114
115 /*
116 * This function is called when lua encounters an error outside of any protected
117 * environment
118 * Throwing the exception through lua code appears to work, even if it was
119 * compiled without -fexceptions. If it turns out, it fails in some conditions,
120 * it could be replaced with some longjmp() magic. But that shouldn't be
121 * necessary, as this function will not be called under normal conditions (we
122 * execute everything in protected mode).
123 */
panic_throw(lua_State * l)124 int panic_throw(lua_State *l) {
125 if (lua_checkstack(l, 1) == 0) { throw std::bad_alloc(); }
126
127 rawgetfield(l, REGISTRYINDEX, this_cpp_object);
128 assert(lua_islightuserdata(l, -1));
129 auto *L = static_cast<state *>(lua_touserdata(l, -1));
130 lua_pop(l, 1);
131
132 throw lua::exception(L);
133 }
134
135 // protected mode wrappers for various lua functions
safe_concat_trampoline(lua_State * l)136 int safe_concat_trampoline(lua_State *l) {
137 lua_concat(l, lua_gettop(l));
138 return 1;
139 }
140
141 template <int (*compare)(lua_State *, int, int)>
safe_compare_trampoline(lua_State * l)142 int safe_compare_trampoline(lua_State *l) {
143 int r = compare(l, 1, 2);
144 lua_pop(l, 2);
145 lua_pushinteger(l, r);
146 return 1;
147 }
148
safe_gc_trampoline(lua_State * l)149 int safe_gc_trampoline(lua_State *l) {
150 int what = lua_tointeger(l, -2);
151 int data = lua_tointeger(l, -1);
152 lua_pop(l, 2);
153 lua_pushinteger(l, lua_gc(l, what, data));
154 return 1;
155 }
156
157 template <void (*misc)(lua_State *, int), int nresults>
safe_misc_trampoline(lua_State * l)158 int safe_misc_trampoline(lua_State *l) {
159 misc(l, 1);
160 return nresults;
161 }
162
163 // Overloaded for Lua 5.3+ as lua_gettable and others return an int
164 template <int (*misc)(lua_State *, int), int nresults>
safe_misc_trampoline(lua_State * l)165 int safe_misc_trampoline(lua_State *l) {
166 misc(l, 1);
167 return nresults;
168 }
169
safe_next_trampoline(lua_State * l)170 int safe_next_trampoline(lua_State *l) {
171 int r = lua_next(l, 1);
172 lua_checkstack(l, 1);
173 lua_pushinteger(l, r);
174 return r != 0 ? 3 : 1;
175 }
176
177 } // namespace
178
get_error_msg(state * L)179 std::string exception::get_error_msg(state *L) {
180 static const std::string default_msg("Unknown lua exception");
181
182 try {
183 return L->tostring(-1);
184 } catch (not_string_error &e) { return default_msg; }
185 }
186
exception(state * l)187 exception::exception(state *l) : std::runtime_error(get_error_msg(l)), L(l) {
188 L->checkstack(1);
189
190 L->rawgetfield(REGISTRYINDEX, lua_exception_namespace);
191 L->insert(-2);
192 key = L->ref(-2);
193 L->pop(1);
194 }
195
~exception()196 exception::~exception() {
197 if (L == nullptr) { return; }
198 L->checkstack(1);
199
200 L->rawgetfield(REGISTRYINDEX, lua_exception_namespace);
201 L->unref(-1, key);
202 L->pop();
203 }
204
push_lua_error(state * l)205 void exception::push_lua_error(state *l) {
206 if (l != L) {
207 throw std::runtime_error(
208 "Cannot transfer exceptions between different lua contexts");
209 }
210 l->checkstack(2);
211
212 l->rawgetfield(REGISTRYINDEX, lua_exception_namespace);
213 l->rawgeti(-1, key);
214 l->replace(-2);
215 }
216
state()217 state::state() {
218 if (lua_State *l = luaL_newstate()) {
219 cobj.reset(l, &lua_close);
220 } else {
221 // docs say this can happen only in case of a memory allocation error
222 throw std::bad_alloc();
223 }
224
225 // set our panic function
226 lua_atpanic(cobj.get(), panic_throw);
227
228 checkstack(2);
229
230 // store a pointer to ourselves
231 pushlightuserdata(this);
232 rawsetfield(REGISTRYINDEX, this_cpp_object);
233
234 // a metatable for C++ exceptions travelling through lua code
235 newmetatable(cpp_exception_metatable);
236 lua_pushcfunction(cobj.get(), &exception_to_string);
237 rawsetfield(-2, "__tostring");
238 pushboolean(false);
239 rawsetfield(-2, "__metatable");
240 pushdestructor<std::exception_ptr>();
241 rawsetfield(-2, "__gc");
242 pop();
243
244 // a metatable for C++ functions callable from lua code
245 newmetatable(cpp_function_metatable);
246 pushboolean(false);
247 rawsetfield(-2, "__metatable");
248 pushdestructor<cpp_function>();
249 rawsetfield(-2, "__gc");
250 pop();
251
252 // while they're travelling through C++ code, lua exceptions will reside here
253 newtable();
254 rawsetfield(REGISTRYINDEX, lua_exception_namespace);
255
256 luaL_openlibs(cobj.get());
257 }
258
call(int nargs,int nresults,int errfunc)259 void state::call(int nargs, int nresults, int errfunc) {
260 int r = lua_pcall(cobj.get(), nargs, nresults, errfunc);
261 if (r == 0) { return; }
262
263 if (r == LUA_ERRMEM) {
264 // memory allocation error, cross your fingers
265 throw std::bad_alloc();
266 }
267
268 checkstack(3);
269 rawgetfield(REGISTRYINDEX, cpp_exception_metatable);
270 if (getmetatable(-2)) {
271 if (rawequal(-1, -2)) {
272 // it's a C++ exception, rethrow it
273 auto *ptr = static_cast<std::exception_ptr *>(touserdata(-3));
274 assert(ptr);
275
276 /*
277 * we create a copy, so we can pop the object without fearing the
278 * exception will be collected by lua's GC
279 */
280 std::exception_ptr t(*ptr);
281 ptr = nullptr;
282 pop(3);
283 std::rethrow_exception(t);
284 }
285 pop(2);
286 }
287 // it's a lua exception, wrap it
288 if (r == LUA_ERRERR) { throw lua::errfunc_error(this); }
289 { throw lua::exception(this); }
290 }
291
checkstack(int extra)292 void state::checkstack(int extra) {
293 if (lua_checkstack(cobj.get(), extra) == 0) { throw std::bad_alloc(); }
294 }
295
concat(int n)296 void state::concat(int n) {
297 assert(n >= 0);
298 checkstack(1);
299 lua_pushcfunction(cobj.get(), safe_concat_trampoline);
300 insert(-n - 1);
301 call(n, 1, 0);
302 }
303
equal(int index1,int index2)304 bool state::equal(int index1, int index2) {
305 // avoid pcall overhead in trivial cases
306 if (rawequal(index1, index2)) { return true; }
307
308 return safe_compare(&safe_compare_trampoline<lua_equal>, index1, index2);
309 }
310
gc(int what,int data)311 int state::gc(int what, int data) {
312 checkstack(3);
313 lua_pushcfunction(cobj.get(), safe_gc_trampoline);
314 pushinteger(what);
315 pushinteger(data);
316 call(2, 1, 0);
317 assert(state::_isnumber(-1));
318 int r = tointeger(-1);
319 pop();
320 return r;
321 }
322
getfield(int index,const char * k)323 void state::getfield(int index, const char *k) {
324 checkstack(1);
325 index = absindex(index);
326 pushstring(k);
327 gettable(index);
328 }
329
getglobal(const char * name)330 void state::getglobal(const char *name) {
331 #if LUA_VERSION_NUM >= 502
332 checkstack(1);
333 pushinteger(LUA_RIDX_GLOBALS);
334 gettable(REGISTRYINDEX);
335 getfield(-1, name);
336 replace(-2);
337 #else
338 getfield(LUA_GLOBALSINDEX, name);
339 #endif
340 }
341
gettable(int index)342 void state::gettable(int index) {
343 checkstack(2);
344 pushvalue(index);
345 insert(-2);
346 lua_pushcfunction(cobj.get(), (&safe_misc_trampoline<&lua_gettable, 1>));
347 insert(-3);
348 call(2, 1, 0);
349 }
350
lessthan(int index1,int index2)351 bool state::lessthan(int index1, int index2) {
352 return safe_compare(&safe_compare_trampoline<&lua_lessthan>, index1, index2);
353 }
354
loadfile(const char * filename)355 void state::loadfile(const char *filename) {
356 switch (luaL_loadfile(cobj.get(), filename)) {
357 case 0:
358 return;
359 case LUA_ERRSYNTAX:
360 throw lua::syntax_error(this);
361 case LUA_ERRFILE:
362 throw lua::file_error(this);
363 case LUA_ERRMEM:
364 throw std::bad_alloc();
365 default:
366 assert(0);
367 }
368 }
369
loadstring(const char * s)370 void state::loadstring(const char *s) {
371 switch (luaL_loadstring(cobj.get(), s)) {
372 case 0:
373 return;
374 case LUA_ERRSYNTAX:
375 throw lua::syntax_error(this);
376 case LUA_ERRMEM:
377 throw std::bad_alloc();
378 default:
379 assert(0);
380 }
381 }
382
next(int index)383 bool state::next(int index) {
384 checkstack(2);
385 pushvalue(index);
386 insert(-2);
387 lua_pushcfunction(cobj.get(), &safe_next_trampoline);
388 insert(-3);
389
390 call(2, MULTRET, 0);
391
392 assert(state::_isnumber(-1));
393 int r = tointeger(-1);
394 pop();
395 return r != 0;
396 }
397
pushclosure(const cpp_function & fn,int n)398 void state::pushclosure(const cpp_function &fn, int n) {
399 checkstack(2);
400
401 createuserdata<cpp_function>(fn);
402 rawgetfield(REGISTRYINDEX, cpp_function_metatable);
403 setmetatable(-2);
404
405 insert(-n - 1);
406 lua_pushcclosure(cobj.get(), &closure_trampoline, n + 1);
407 }
408
rawgetfield(int index,const char * k)409 void state::rawgetfield(int index, const char *k) {
410 lua::rawgetfield(cobj.get(), index, k);
411 }
412
rawsetfield(int index,const char * k)413 void state::rawsetfield(int index, const char *k) {
414 lua::rawsetfield(cobj.get(), index, k);
415 }
416
safe_compare(lua_CFunction trampoline,int index1,int index2)417 bool state::safe_compare(lua_CFunction trampoline, int index1, int index2) {
418 // if one of the indexes is invalid, return false
419 if (isnone(index1) || isnone(index2)) { return false; }
420
421 // convert relative indexes into absolute
422 index1 = absindex(index1);
423 index2 = absindex(index2);
424
425 checkstack(3);
426 lua_pushcfunction(cobj.get(), trampoline);
427 pushvalue(index1);
428 pushvalue(index2);
429 call(2, 1, 0);
430 assert(state::_isnumber(-1));
431 int r = tointeger(-1);
432 pop();
433 return r != 0;
434 }
435
setfield(int index,const char * k)436 void state::setfield(int index, const char *k) {
437 checkstack(1);
438 index = absindex(index);
439 pushstring(k);
440 insert(-2);
441 settable(index);
442 }
443
setglobal(const char * name)444 void state::setglobal(const char *name) {
445 #if LUA_VERSION_NUM >= 502
446 stack_sentry s(*this, -1);
447 checkstack(1);
448 pushinteger(LUA_RIDX_GLOBALS);
449 gettable(REGISTRYINDEX);
450 insert(-2);
451 setfield(-2, name);
452 pop();
453 #else
454 setfield(LUA_GLOBALSINDEX, name);
455 #endif
456 }
457
settable(int index)458 void state::settable(int index) {
459 checkstack(2);
460 pushvalue(index);
461 insert(-3);
462 lua_pushcfunction(cobj.get(), (&safe_misc_trampoline<&lua_settable, 0>));
463 insert(-4);
464 call(3, 0, 0);
465 }
466
tostring(int index)467 std::string state::tostring(int index) {
468 size_t len;
469 const char *str = lua_tolstring(cobj.get(), index, &len);
470 if (str == nullptr) { throw not_string_error(); }
471 return std::string(str, len);
472 }
473 } // namespace lua
474