Function symbexec

Source/Misc/lua/src/lua.c:4825–4983

static Instruction symbexec (const Proto *pt, int lastpc, int reg) {
int pc;
int last;  /* stores position of last instruction that changed `reg' */
last = pt->sizecode-1;  /* points to final return (a `neutral' instruction) */
check(precheck(pt));
for (pc = 0; pc < lastpc; pc++) {
Instruction i = pt->code[pc];
OpCode op = GET_OPCODE(i);
int a = GETARG_A(i);
int b = 0;
int c = 0;
check(op < NUM_OPCODES);
checkreg(pt, a);
switch (getOpMode(op)) {
case iABC: {
b = GETARG_B(i);
c = GETARG_C(i);
check(checkArgMode(pt, b, getBMode(op)));
check(checkArgMode(pt, c, getCMode(op)));
break;
}
case iABx: {
b = GETARG_Bx(i);
if (getBMode(op) == OpArgK) check(b < pt->sizek);
break;
}
case iAsBx: {
b = GETARG_sBx(i);
if (getBMode(op) == OpArgR) {
int dest = pc+1+b;
check(0 <= dest && dest < pt->sizecode);
if (dest > 0) {
int j;
/* check that it does not jump to a setlist count; this
is tricky, because the count from a previous setlist may
have the same value of an invalid setlist; so, we must
go all the way back to the first of them (if any) */
for (j = 0; j < dest; j++) {
Instruction d = pt->code[dest-1-j];
if (!(GET_OPCODE(d) == OP_SETLIST && GETARG_C(d) == 0)) break;
}
/* if 'j' is even, previous value is not a setlist (even if
it looks like one) */
check((j&1) == 0);
}
}
break;
}
}
if (testAMode(op)) {
if (a == reg) last = pc;  /* change register `a' */
}
if (testTMode(op)) {
check(pc+2 < pt->sizecode);  /* check skip */
check(GET_OPCODE(pt->code[pc+1]) == OP_JMP);
}
switch (op) {
case OP_LOADBOOL: {