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Fix lua failure to catch divide by zero and NaN exceptions

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I can only assume in the course of the original conversion to fixed point
math in RbLua the fact that division by zero and NaN handling was to be
caught as a graceful exception by the floating point handler was overlooked.

As a result lua doesn't handle these exceptions and instead results in a
panic on the device.

This patch fixes this handling in the lexer for compile time Inf and Nan
results and in the luavm for runtime division by zero (Inf)

I missed the runtime exception of n%0 added checks for that as well..

Change-Id: I7746c087ea93678e5875f15ec6fe3f29f26bdb31
This commit is contained in:
William Wilgus 2018-02-05 07:28:08 +01:00
parent 80bb6ccdc4
commit 9a9c7f2b7c
2 changed files with 33 additions and 8 deletions
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13
apps/plugins/lua/lcode.c
View file

@ -642,26 +642,27 @@ static int constfolding (OpCode op, expdesc *e1, expdesc *e2) {
case OP_SUB: r = luai_numsub(v1, v2); break;
case OP_MUL: r = luai_nummul(v1, v2); break;
case OP_DIV:
if (v2 == 0) return 0; /* do not attempt to divide by 0 */
if (v2 == 0) return -1; /* do not attempt to divide by 0 */
r = luai_numdiv(v1, v2); break;
case OP_MOD:
if (v2 == 0) return 0; /* do not attempt to divide by 0 */
if (v2 == 0) return -1; /* do not attempt to divide by 0 */
r = luai_nummod(v1, v2); break;
case OP_POW: r = luai_numpow(v1, v2); break;
case OP_UNM: r = luai_numunm(v1); break;
case OP_LEN: return 0; /* no constant folding for 'len' */
default: lua_assert(0); r = 0; break;
}
if (luai_numisnan(r)) return 0; /* do not attempt to produce NaN */
if (luai_numisnan(r)) return -2; /* do not attempt to produce NaN */
e1->u.nval = r;
return 1;
}
static void codearith (FuncState *fs, OpCode op, expdesc *e1, expdesc *e2) {
if (constfolding(op, e1, e2))
int resf = constfolding(op, e1, e2);
if (resf > 0)
return;
else {
else if (resf == 0) {
int o2 = (op != OP_UNM && op != OP_LEN) ? luaK_exp2RK(fs, e2) : 0;
int o1 = luaK_exp2RK(fs, e1);
if (o1 > o2) {
@ -675,6 +676,8 @@ static void codearith (FuncState *fs, OpCode op, expdesc *e1, expdesc *e2) {
e1->u.s.info = luaK_codeABC(fs, op, 0, o1, o2);
e1->k = VRELOCABLE;
}
else
luaX_syntaxerror(fs->ls, "Inf or NaN");
}

28
apps/plugins/lua/lvm.c
View file

@ -480,13 +480,35 @@ void luaV_execute (lua_State *L, int nexeccalls) {
continue;
}
case OP_DIV: {
arith_op(luai_numdiv, TM_DIV);
TValue *rb = RKB(i);
TValue *rc = RKC(i);
if (ttisnumber(rb) && ttisnumber(rc)) {
lua_Number nb = nvalue(rb), nc = nvalue(rc);
if (nc == 0)
luaG_typeerror(L, rc, "divide by zero");
setnvalue(ra, luai_numdiv(nb, nc));
}
else
Protect(Arith(L, ra, rb, rc, TM_DIV));
continue;
}
case OP_MOD: {
arith_op(luai_nummod, TM_MOD);
TValue *rb = RKB(i);
TValue *rc = RKC(i);
if (ttisnumber(rb) && ttisnumber(rc)) {
lua_Number nb = nvalue(rb), nc = nvalue(rc);
if (nc == 0)
luaG_typeerror(L, rc, "perform 'n%0'");
setnvalue(ra, luai_nummod(nb, nc));
}
else
Protect(Arith(L, ra, rb, rc, TM_MOD));
continue;
}
}
case OP_POW: {
arith_op(luai_numpow, TM_POW);
continue;