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Avoid negation of signed integers in C that may hold INT*_MIN.

Browse Source 
Reported by minoki.
Recent C compilers 'take advantage' of the undefined behavior.
This completely changes the meaning of expressions like (k == -k).
This commit is contained in:
Mike Pall 2022-12-22 00:03:06 +01:00
parent b2791179ef
commit 8a5e398c52
12 changed files with 32 additions and 32 deletions
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4
src/lib_bit.c
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@ -55,8 +55,8 @@ LJLIB_CF(bit_tohex)
int32_t i, n = L->base+1 >= L->top ? 8 : lj_lib_checkbit(L, 2);
const char *hexdigits = "0123456789abcdef";
char buf[8];
if (n < 0) { n = -n; hexdigits = "0123456789ABCDEF"; }
if (n > 8) n = 8;
if (n < 0) { n = (int32_t)(~(uint32_t)n+1u); hexdigits = "0123456789ABCDEF"; }
if ((uint32_t)n > 8) n = 8;
for (i = n; --i >= 0; ) { buf[i] = hexdigits[b & 15]; b >>= 4; }
lua_pushlstring(L, buf, (size_t)n);
return 1;

2
src/lj_asm_mips.h
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@ -1227,7 +1227,7 @@ static void asm_arithov(ASMState *as, IRIns *ir)
Reg right, left, tmp, dest = ra_dest(as, ir, RSET_GPR);
if (irref_isk(ir->op2)) {
int k = IR(ir->op2)->i;
if (ir->o == IR_SUBOV) k = -k;
if (ir->o == IR_SUBOV) k = (int)(~(unsigned int)k+1u);
if (checki16(k)) { /* (dest < left) == (k >= 0 ? 1 : 0) */
left = ra_alloc1(as, ir->op1, RSET_GPR);
asm_guard(as, k >= 0 ? MIPSI_BNE : MIPSI_BEQ, RID_TMP, RID_ZERO);

2
src/lj_carith.c
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@ -205,7 +205,7 @@ static int carith_int64(lua_State *L, CTState *cts, CDArith *ca, MMS mm)
else
*up = lj_carith_powu64(u0, u1);
break;
case MM_unm: *up = (uint64_t)-(int64_t)u0; break;
case MM_unm: *up = ~u0+1u; break;
default: lua_assert(0); break;
}
lj_gc_check(L);

2
src/lj_cparse.c
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@ -477,7 +477,7 @@ static void cp_expr_prefix(CPState *cp, CPValue *k)
} else if (cp_opt(cp, '+')) {
cp_expr_unary(cp, k); /* Nothing to do (well, integer promotion). */
} else if (cp_opt(cp, '-')) {
cp_expr_unary(cp, k); k->i32 = -k->i32;
cp_expr_unary(cp, k); k->i32 = (int32_t)(~(uint32_t)k->i32+1);
} else if (cp_opt(cp, '~')) {
cp_expr_unary(cp, k); k->i32 = ~k->i32;
} else if (cp_opt(cp, '!')) {

2
src/lj_ctype.c
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@ -577,7 +577,7 @@ GCstr *lj_ctype_repr_int64(lua_State *L, uint64_t n, int isunsigned)
if (isunsigned) {
*--p = 'U';
} else if ((int64_t)n < 0) {
n = (uint64_t)-(int64_t)n;
n = ~n+1u;
sign = 1;
}
do { *--p = (char)('0' + n % 10); } while (n /= 10);

2
src/lj_emit_arm.h
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@ -154,7 +154,7 @@ static int emit_kdelta2(ASMState *as, Reg d, int32_t i)
if (other) {
int32_t delta = i - other;
uint32_t sh, inv = 0, k2, k;
if (delta < 0) { delta = -delta; inv = ARMI_ADD^ARMI_SUB; }
if (delta < 0) { delta = (int32_t)(~(uint32_t)delta+1u); inv = ARMI_ADD^ARMI_SUB; }
sh = lj_ffs(delta) & ~1;
k2 = emit_isk12(0, delta & (255 << sh));
k = emit_isk12(0, delta & ~(255 << sh));

2
src/lj_obj.h
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@ -327,7 +327,7 @@ typedef struct GCproto {
#define PROTO_UV_IMMUTABLE 0x4000 /* Immutable upvalue. */
#define proto_kgc(pt, idx) \
check_exp((uintptr_t)(intptr_t)(idx) >= (uintptr_t)-(intptr_t)(pt)->sizekgc, \
check_exp((uintptr_t)(intptr_t)(idx) >= ~(uintptr_t)(pt)->sizekgc+1u, \
gcref(mref((pt)->k, GCRef)[(idx)]))
#define proto_knumtv(pt, idx) \
check_exp((uintptr_t)(idx) < (pt)->sizekn, &mref((pt)->k, TValue)[(idx)])

6
src/lj_opt_fold.c
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@ -236,7 +236,7 @@ static int32_t kfold_intop(int32_t k1, int32_t k2, IROp op)
case IR_SUB: k1 -= k2; break;
case IR_MUL: k1 *= k2; break;
case IR_MOD: k1 = lj_vm_modi(k1, k2); break;
case IR_NEG: k1 = -k1; break;
case IR_NEG: k1 = (int32_t)(~(uint32_t)k1+1u); break;
case IR_BAND: k1 &= k2; break;
case IR_BOR: k1 |= k2; break;
case IR_BXOR: k1 ^= k2; break;
@ -1160,7 +1160,7 @@ LJFOLDF(simplify_intsub_k)
if (fright->i == 0) /* i - 0 ==> i */
return LEFTFOLD;
fins->o = IR_ADD; /* i - k ==> i + (-k) */
fins->op2 = (IRRef1)lj_ir_kint(J, -fright->i); /* Overflow for -2^31 ok. */
fins->op2 = (IRRef1)lj_ir_kint(J, (int32_t)(~(uint32_t)fright->i+1u)); /* Overflow for -2^31 ok. */
return RETRYFOLD;
}
@ -1191,7 +1191,7 @@ LJFOLDF(simplify_intsub_k64)
if (k == 0) /* i - 0 ==> i */
return LEFTFOLD;
fins->o = IR_ADD; /* i - k ==> i + (-k) */
fins->op2 = (IRRef1)lj_ir_kint64(J, (uint64_t)-(int64_t)k);
fins->op2 = (IRRef1)lj_ir_kint64(J, ~k+1u);
return RETRYFOLD;
}

12
src/lj_parse.c
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@ -951,22 +951,22 @@ static void bcemit_unop(FuncState *fs, BCOp op, ExpDesc *e)
#if LJ_HASFFI
if (e->k == VKCDATA) { /* Fold in-place since cdata is not interned. */
GCcdata *cd = cdataV(&e->u.nval);
int64_t *p = (int64_t *)cdataptr(cd);
uint64_t *p = (uint64_t *)cdataptr(cd);
if (cd->ctypeid == CTID_COMPLEX_DOUBLE)
p[1] ^= (int64_t)U64x(80000000,00000000);
p[1] ^= U64x(80000000,00000000);
else
*p = -*p;
*p = ~*p+1u;
return;
} else
#endif
if (expr_isnumk(e) && !expr_numiszero(e)) { /* Avoid folding to -0. */
TValue *o = expr_numtv(e);
if (tvisint(o)) {
int32_t k = intV(o);
if (k == -k)
int32_t k = intV(o), negk = (int32_t)(~(uint32_t)k+1u);
if (k == negk)
setnumV(o, -(lua_Number)k);
else
setintV(o, -k);
setintV(o, negk);
return;
} else {
o->u64 ^= U64x(80000000,00000000);

2
src/lj_str.c
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@ -190,7 +190,7 @@ size_t LJ_FASTCALL lj_str_bufnum(char *s, cTValue *o)
/* Print integer to buffer. Returns pointer to start. */
char * LJ_FASTCALL lj_str_bufint(char *p, int32_t k)
{
uint32_t u = (uint32_t)(k < 0 ? -k : k);
uint32_t u = k < 0 ? ~(uint32_t)k+1u : (uint32_t)k;
p += 1+10;
do { *--p = (char)('0' + u % 10); } while (u /= 10);
if (k < 0) *--p = '-';

20
src/lj_strscan.c
View File

@ -124,19 +124,19 @@ static StrScanFmt strscan_hex(const uint8_t *p, TValue *o,
case STRSCAN_INT:
if (!(opt & STRSCAN_OPT_TONUM) && x < 0x80000000u+neg &&
!(x == 0 && neg)) {
o->i = neg ? -(int32_t)x : (int32_t)x;
o->i = neg ? (int32_t)(~x+1u) : (int32_t)x;
return STRSCAN_INT; /* Fast path for 32 bit integers. */
}
if (!(opt & STRSCAN_OPT_C)) { fmt = STRSCAN_NUM; break; }
/* fallthrough */
case STRSCAN_U32:
if (dig > 8) return STRSCAN_ERROR;
o->i = neg ? -(int32_t)x : (int32_t)x;
o->i = neg ? (int32_t)(~x+1u) : (int32_t)x;
return STRSCAN_U32;
case STRSCAN_I64:
case STRSCAN_U64:
if (dig > 16) return STRSCAN_ERROR;
o->u64 = neg ? (uint64_t)-(int64_t)x : x;
o->u64 = neg ? ~x+1u : x;
return fmt;
default:
break;
@ -168,12 +168,12 @@ static StrScanFmt strscan_oct(const uint8_t *p, TValue *o,
/* fallthrough */
case STRSCAN_U32:
if ((x >> 32)) return STRSCAN_ERROR;
o->i = neg ? -(int32_t)x : (int32_t)x;
o->i = neg ? (int32_t)(~(uint32_t)x+1u) : (int32_t)x;
break;
default:
case STRSCAN_I64:
case STRSCAN_U64:
o->u64 = neg ? (uint64_t)-(int64_t)x : x;
o->u64 = neg ? ~x+1u : x;
break;
}
return fmt;
@ -229,18 +229,18 @@ static StrScanFmt strscan_dec(const uint8_t *p, TValue *o,
switch (fmt) {
case STRSCAN_INT:
if (!(opt & STRSCAN_OPT_TONUM) && x < 0x80000000u+neg) {
o->i = neg ? -(int32_t)x : (int32_t)x;
o->i = neg ? (int32_t)(~x+1u) : (int32_t)x;
return STRSCAN_INT; /* Fast path for 32 bit integers. */
}
if (!(opt & STRSCAN_OPT_C)) { fmt = STRSCAN_NUM; goto plainnumber; }
/* fallthrough */
case STRSCAN_U32:
if ((x >> 32) != 0) return STRSCAN_ERROR;
o->i = neg ? -(int32_t)x : (int32_t)x;
o->i = neg ? (int32_t)(~x+1u) : (int32_t)x;
return STRSCAN_U32;
case STRSCAN_I64:
case STRSCAN_U64:
o->u64 = neg ? (uint64_t)-(int64_t)x : x;
o->u64 = neg ? ~x+1u : x;
return fmt;
default:
plainnumber: /* Fast path for plain numbers < 2^63. */
@ -418,7 +418,7 @@ StrScanFmt lj_strscan_scan(const uint8_t *p, TValue *o, uint32_t opt)
if (xx >= STRSCAN_MAXEXP) return STRSCAN_ERROR;
p++;
}
ex += negx ? -(int32_t)xx : (int32_t)xx;
ex += negx ? (int32_t)(~xx+1u) : (int32_t)xx;
}
/* Parse suffix. */
@ -456,7 +456,7 @@ StrScanFmt lj_strscan_scan(const uint8_t *p, TValue *o, uint32_t opt)
o->n = -0.0;
return STRSCAN_NUM;
} else {
o->i = neg ? -(int32_t)x : (int32_t)x;
o->i = neg ? (int32_t)(~x+1u) : (int32_t)x;
return STRSCAN_INT;
}
}

8
src/lj_vmmath.c
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@ -66,11 +66,11 @@ int32_t LJ_FASTCALL lj_vm_modi(int32_t a, int32_t b)
{
uint32_t y, ua, ub;
lua_assert(b != 0); /* This must be checked before using this function. */
ua = a < 0 ? (uint32_t)-a : (uint32_t)a;
ub = b < 0 ? (uint32_t)-b : (uint32_t)b;
ua = a < 0 ? ~(uint32_t)a+1u : (uint32_t)a;
ub = b < 0 ? ~(uint32_t)b+1u : (uint32_t)b;
y = ua % ub;
if (y != 0 && (a^b) < 0) y = y - ub;
if (((int32_t)y^b) < 0) y = (uint32_t)-(int32_t)y;
if (((int32_t)y^b) < 0) y = ~y+1u;
return (int32_t)y;
}
#endif
@ -105,7 +105,7 @@ double lj_vm_powi(double x, int32_t k)
else if (k == 0)
return 1.0;
else
return 1.0 / lj_vm_powui(x, (uint32_t)-k);
return 1.0 / lj_vm_powui(x, ~(uint32_t)k+1u);
}
/* Computes fpm(x) for extended math functions. */