本文共 3134 字，大约阅读时间需要 10 分钟。

前言

lua_State中有C程序注册到lua的接口函数指针

试验

对于一个L, 从头到尾是不变的.

void luaV_execute(lua_State* L){    int iDebug = 0;    int bp = 0;    CallInfo* ci = L->ci;    LClosure* cl;    TValue* k;    StkId base = NULL;    StkId baseFirst = NULL;    ci->callstatus |= CIST_FRESH;  /* fresh invocation of 'luaV_execute" */newframe:  /* reentry point when frame changes (call/return) */    lua_assert(ci == L->ci);    cl = clLvalue(ci->func);  /* local reference to function's closure */    k = cl->p->k;  /* local reference to function's constant table */    base = ci->u.l.base;  /* local copy of function's base */    baseFirst = base;    /* main loop of interpreter */    for (;;) {        Instruction i;        Instruction iTmp;        StkId ra = NULL;        if (++iDebug == 9) {            bp = bp;        }        if (baseFirst != base) {            bp = bp;        }        // @todo modify by ls        // vmfetch(); // original        /* fetch an instruction and prepare its execution */        if (1)   {            i = *(ci->u.l.savedpc++);            if (L->hookmask & (LUA_MASKLINE | LUA_MASKCOUNT)) {                Protect(luaG_traceexec(L));            }            // #define getarg(i,pos,size)  (cast(int, ((i)>>pos) & MASK1(size,0)))            // #define SIZE_A 8            // #define POS_A       (POS_OP + SIZE_OP)            // #define SIZE_OP     6            // #define POS_OP      0            // ra = base + getarg(i, POS_A, SIZE_A);            // ra = base + getarg(i, 6, 8);            iTmp = (i >> 6);            ra = base + ((i >> 6) & 0xff); // 这里得到了ra怎么算得，下面的函数继续用ra算f            lua_assert(base == ci->u.l.base);            lua_assert(base <= L->top && L->top < L->stack + L->stacksize);        }

vmcase(OP_CALL) {                int b = GETARG_B(i);                int nresults = GETARG_C(i) - 1;                if (b != 0) {                    L->top = ra + b;    /* else previous instruction set top */                }                // 这里调用C接口函数, 将ra传进去，继续算f                if (luaD_precall(L, ra, nresults)) {  /* C function? */                     if (nresults >= 0) {                        L->top = ci->top;    /* adjust results */                    }                    Protect((void)0);  /* update 'base' */                } else { /* Lua function */                    ci = L->ci;                    goto newframe;  /* restart luaV_execute over new Lua function */                }                vmbreak;

int luaD_precall(lua_State* L, StkId func, int nresults){    int bp = 0;    lua_CFunction f = NULL;    CallInfo* ci;    switch (ttype(func)) {        case LUA_TCCL:  /* C closure */            f = clCvalue(func)->f;            goto Cfunc;        case LUA_TLCF:  /* light C function */            // @todo modify by ls            // f = fvalue(func); // original            ttislcf(func); // 这里判断了func是否为C函数, 不是抛异常            f = func->value_.f; // 这里得到C函数指针f            bp = bp;

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