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better(?) implementation for 'pcall'/'xpcall' (regarding the insertion

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of the boolean first result)
This commit is contained in:
Roberto Ierusalimschy
2014-05-16 15:54:01 -03:00
parent 17159b491c
commit e2be310a85
1 changed files with 35 additions and 20 deletions
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55
lbaselib.c
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@@ -1,5 +1,5 @@
/* /*
** $Id: lbaselib.c,v 1.285 2014/03/12 20:57:40 roberto Exp roberto $ ** $Id: lbaselib.c,v 1.286 2014/05/01 18:18:06 roberto Exp roberto $
** Basic library ** Basic library
** See Copyright Notice in lua.h ** See Copyright Notice in lua.h
*/ */
@@ -379,44 +379,59 @@ static int luaB_select (lua_State *L) {
} }
static int finishpcall (lua_State *L, int status) { /*
if (!lua_checkstack(L, 1)) { /* no space for extra boolean? */ ** Finishes a 'pcall' or 'xpcall'. Both functions already pushed a
lua_settop(L, 0); /* create space for return values */ ** 'true' before doing the call, so in case of sucess 'finishpcall'
lua_pushboolean(L, 0); ** only has to return everything in the stack minus 'extra' values
lua_pushstring(L, "stack overflow"); ** (where 'extra' is exactly the number of items to be ignored).
*/
static int finishpcall (lua_State *L, int ok, int extra) {
if (!ok) { /* error? */
lua_pushboolean(L, 0); /* first result (false) */
lua_pushvalue(L, -2); /* error message */
return 2; /* return false, msg */ return 2; /* return false, msg */
} }
lua_pushboolean(L, status); /* first result (status) */ else
lua_replace(L, 1); /* put first result in first slot */ return lua_gettop(L) - extra; /* return all results */
return lua_gettop(L);
} }
/*
** Continuation function for 'pcall' and 'xpcall': get appropriate
** state through 'lua_getctx' and call 'finishpcall' to finish the
** original function.
*/
static int pcallcont (lua_State *L) { static int pcallcont (lua_State *L) {
int status = lua_getctx(L, NULL); int extra;
return finishpcall(L, (status == LUA_YIELD)); int status = lua_getctx(L, &extra);
return finishpcall(L, (status == LUA_YIELD), extra);
} }
static int luaB_pcall (lua_State *L) { static int luaB_pcall (lua_State *L) {
int status; int status;
luaL_checkany(L, 1); luaL_checkany(L, 1);
lua_pushnil(L); lua_pushboolean(L, 1); /* first result if no errors */
lua_insert(L, 1); /* create space for status result */ lua_insert(L, 1); /* put it in place */
status = lua_pcallk(L, lua_gettop(L) - 2, LUA_MULTRET, 0, 0, pcallcont); status = lua_pcallk(L, lua_gettop(L) - 2, LUA_MULTRET, 0, 0, pcallcont);
return finishpcall(L, (status == LUA_OK)); return finishpcall(L, (status == LUA_OK), 0);
} }
/*
** Do a protected call with error handling. After 'lua_rotate', the
** stack will have <f, err, true, f, [args...]>; so, the function passes
** 2 to 'finishpcall' to skip the 2 first values when returning results.
*/
static int luaB_xpcall (lua_State *L) { static int luaB_xpcall (lua_State *L) {
int status; int status;
int n = lua_gettop(L); int n = lua_gettop(L);
luaL_argcheck(L, n >= 2, 2, "value expected"); luaL_checktype(L, 2, LUA_TFUNCTION); /* check error function */
lua_pushvalue(L, 1); /* exchange function... */ lua_pushboolean(L, 1); /* first result */
lua_copy(L, 2, 1); /* ...and error handler */ lua_pushvalue(L, 1); /* function */
lua_replace(L, 2); lua_rotate(L, 3, 2); /* move them below function's arguments */
status = lua_pcallk(L, n - 2, LUA_MULTRET, 1, 0, pcallcont); status = lua_pcallk(L, n - 2, LUA_MULTRET, 2, 2, pcallcont);
return finishpcall(L, (status == LUA_OK)); return finishpcall(L, (status == LUA_OK), 2);
} }