lua 5.1
lua_State L = luaL_newstate();在使用lua API 时第一步经常是上面这句话，那么 lua_State 到底是什么东西？
先看看下面对 luaL_newstate() 的实现
// luaxlib.h LUALIB_API lua_State *(luaL_newstate) (void); // luaxlib.c LUALIB_API lua_State *luaL_newstate (void) { lua_State *L = lua_newstate(l_alloc, NULL); if (L) lua_atpanic(L, &panic); return L; }继续看 luaL_newstate 是怎么创建 lua_State 的
LUA_API lua_State *lua_newstate (lua_Alloc f, void *ud) { int i; lua_State *L; global_State *g; void *l = (*f)(ud, NULL, 0, state_size(LG)); if (l == NULL) return NULL; L = tostate(l); ... return L; }可见在调用 luaL_newstate 时创建的是 LG 类型的对象，继续看 LG 的定义。
lua 5.2 之后
/* ** thread state + extra space */ typedef struct LX { lu_byte extra_[LUA_EXTRASPACE]; lua_State l; } LX; /* ** Main thread combines a thread state and the global state */ typedef struct LG { LX l; global_State g; } LG;由此可见 LG 是一个包含了线程状态即 lua_State 和 全局状态的结构体。 即，我们在调用 luaL_newstate 是创建了 LG，给我们返回的是 LG 的属性 lua_State 而 global_State 对我们来说是不可见的。
一下是对 lua_State 和 global_State 的定义
/* ** `per thread' state */ struct lua_State { CommonHeader; lu_byte status; StkId top; /* first free slot in the stack */ StkId base; /* base of current function */ global_State *l_G; CallInfo *ci; /* call info for current function */ const Instruction *savedpc; /* `savedpc' of current function */ StkId stack_last; /* last free slot in the stack */ StkId stack; /* stack base */ CallInfo *end_ci; /* points after end of ci array*/ CallInfo *base_ci; /* array of CallInfo's */ int stacksize; int size_ci; /* size of array `base_ci' */ unsigned short nCcalls; /* number of nested C calls */ unsigned short baseCcalls; /* nested C calls when resuming coroutine */ lu_byte hookmask; lu_byte allowhook; int basehookcount; int hookcount; lua_Hook hook; TValue l_gt; /* table of globals */ TValue env; /* temporary place for environments */ GCObject *openupval; /* list of open upvalues in this stack */ GCObject *gclist; struct lua_longjmp *errorJmp; /* current error recover point */ ptrdiff_t errfunc; /* current error handling function (stack index) */ }; /* ** `global state', shared by all threads of this state */ typedef struct global_State { stringtable strt; /* hash table for strings */ lua_Alloc frealloc; /* function to reallocate memory */ void *ud; /* auxiliary data to `frealloc' */ lu_byte currentwhite; lu_byte gcstate; /* state of garbage collector */ int sweepstrgc; /* position of sweep in `strt' */ GCObject *rootgc; /* list of all collectable objects */ GCObject **sweepgc; /* position of sweep in `rootgc' */ GCObject *gray; /* list of gray objects */ GCObject *grayagain; /* list of objects to be traversed atomically */ GCObject *weak; /* list of weak tables (to be cleared) */ GCObject *tmudata; /* last element of list of userdata to be GC */ Mbuffer buff; /* temporary buffer for string concatentation */ lu_mem GCthreshold; lu_mem totalbytes; /* number of bytes currently allocated */ lu_mem estimate; /* an estimate of number of bytes actually in use */ lu_mem gcdept; /* how much GC is `behind schedule' */ int gcpause; /* size of pause between successive GCs */ int gcstepmul; /* GC `granularity' */ lua_CFunction panic; /* to be called in unprotected errors */ TValue l_registry; struct lua_State *mainthread; UpVal uvhead; /* head of double-linked list of all open upvalues */ struct Table *mt[NUM_TAGS]; /* metatables for basic types */ TString *tmname[TM_N]; /* array with tag-method names */ } global_State;转载于:https://www.cnblogs.com/pmsl/p/8529341.html
