a = 1
b = 2
c = a + b

static void exprstat (LexState *ls) { /* stat -> func | assignment */FuncState *fs = ls->fs; struct LHS_assign v;/*保存等号左边的变量名*/primaryexp(ls, &v.v);/*处理等号左边的变量名*/if (v.v.k == VCALL) /* stat -> func */SETARG_C(getcode(fs, &v.v), 1); /* call statement uses no results */else { /* stat -> assignment */v.prev = NULL; assignment(ls, &v, 1); } }

static void singlevar (LexState *ls, expdesc *var) {TString *varname = str_checkname(ls);FuncState *fs = ls->fs;if (singlevaraux(fs, varname, var, 1) == VGLOBAL)var->u.s.info = luaK_stringK(fs, varname);  /* info points to global name *//*指向变量名在寄存器的索引值*/
}

static int singlevaraux (FuncState *fs, TString *n, expdesc *var, int base) {if (fs == NULL) {  /* no more levels? */init_exp(var, VGLOBAL, NO_REG);  /* default is global variable */return VGLOBAL;}else {int v = searchvar(fs, n);  /* look up at current level */if (v >= 0) {init_exp(var, VLOCAL, v);if (!base)markupval(fs, v);  /* local will be used as an upval */return VLOCAL;}else {  /* not found at current level; try upper one */if (singlevaraux(fs->prev, n, var, 0) == VGLOBAL)/**/return VGLOBAL;var->u.s.info = indexupvalue(fs, n, var);  /* else was LOCAL or UPVAL */var->k = VUPVAL;  /* upvalue in this level */return VUPVAL;}}
}

static int addk (FuncState *fs, TValue *k, TValue *v) {lua_State *L = fs->L;TValue *idx = luaH_set(L, fs->h, k);Proto *f = fs->f;int oldsize = f->sizek;if (ttisnumber(idx)) {lua_assert(luaO_rawequalObj(&fs->f->k[cast_int(nvalue(idx))], v));return cast_int(nvalue(idx));}else {  /* constant not found; create a new entry */setnvalue(idx, cast_num(fs->nk));luaM_growvector(L, f->k, fs->nk, f->sizek, TValue,MAXARG_Bx, "constant table overflow");while (oldsize < f->sizek) setnilvalue(&f->k[oldsize++]);setobj(L, &f->k[fs->nk], v);luaC_barrier(L, f, v);return fs->nk++;}
}

static void assignment (LexState *ls, struct LHS_assign *lh, int nvars) {expdesc e;check_condition(ls, VLOCAL <= lh->v.k && lh->v.k <= VINDEXED,"syntax error");if (testnext(ls, ',')) {  /* assignment -> `,' primaryexp assignment */struct LHS_assign nv;nv.prev = lh;primaryexp(ls, &nv.v);if (nv.v.k == VLOCAL)check_conflict(ls, lh, &nv.v);assignment(ls, &nv, nvars+1);}else {  /* assignment -> `=' explist1 */int nexps;checknext(ls, '=');nexps = explist1(ls, &e);/*解析等号右边的值*/if (nexps != nvars) {adjust_assign(ls, nvars, nexps, &e);if (nexps > nvars)ls->fs->freereg -= nexps - nvars;  /* remove extra values */}else {luaK_setoneret(ls->fs, &e);  /* close last expression */luaK_storevar(ls->fs, &lh->v, &e);/*生成指令*/return;  /* avoid default */}}init_exp(&e, VNONRELOC, ls->fs->freereg-1);  /* default assignment */luaK_storevar(ls->fs, &lh->v, &e);
}

static void simpleexp (LexState *ls, expdesc *v) {/* simpleexp -> NUMBER | STRING | NIL | true | false | ... |constructor | FUNCTION body | primaryexp */switch (ls->t.token) {case TK_NUMBER: {init_exp(v, VKNUM, 0);/*传入寄存器位置为0*/v->u.nval = ls->t.seminfo.r;/*将浮点数1.0赋值给v->u.navl*/break;}case …………………………}luaX_next(ls);
}

void luaK_storevar (FuncState *fs, expdesc *var, expdesc *ex) {switch (var->k) {case VLOCAL: {freeexp(fs, ex);exp2reg(fs, ex, var->u.s.info);return;}case VUPVAL: {int e = luaK_exp2anyreg(fs, ex);luaK_codeABC(fs, OP_SETUPVAL, e, var->u.s.info, 0);break;}case VGLOBAL: {/*本例中是全局变量*/int e = luaK_exp2anyreg(fs, ex);//返回寄存器索引luaK_codeABx(fs, OP_SETGLOBAL, e, var->u.s.info);//生成指令break;}case VINDEXED: {int e = luaK_exp2RK(fs, ex);luaK_codeABC(fs, OP_SETTABLE, var->u.s.info, var->u.s.aux, e);break;}default: {lua_assert(0);  /* invalid var kind to store */break;}}freeexp(fs, ex);
}

int luaK_codeABx (FuncState *fs, OpCode o, int a, unsigned int bc) {lua_assert(getOpMode(o) == iABx || getOpMode(o) == iAsBx);lua_assert(getCMode(o) == OpArgN);return luaK_code(fs, CREATE_ABx(o, a, bc), fs->ls->lastline);
}