eval: Fix range check of double during conversion to int

2⁶⁴-1 and 2⁶³-1 are not representable as double and get rounded to
2⁶⁴ and 2⁶³ respectively, which are outside the range of 64-bit
[u]int.

This causes undefined behavior when a constant expression is evaluated
that involves a conversion of a very large or small value to an
integer type.

To fix this, change the > to >= and use constants representable as
double.

1 files changed, 2 insertions, 2 deletions

diff --git a/eval.c b/eval.c
index 908ce8d..9b6b33c 100644
--- a/eval.c
+++ b/eval.c
@@ -162,11 +162,11 @@ eval(struct expr *expr, enum evalkind kind)
 					expr->u.constant.f = l->u.constant.u;
 			} else if (l->type->prop & PROPFLOAT && t->prop & PROPINT) {
 				if (t->u.basic.issigned) {
-					if (l->u.constant.f < -1 - 0x7fffffffffffffff || l->u.constant.f > 0x7fffffffffffffff)
+					if (l->u.constant.f < -0x1p63 || l->u.constant.f >= 0x1p63)
 						error(&tok.loc, "integer part of floating-point constant %g cannot be represented as signed integer", l->u.constant.f);
 					expr->u.constant.i = l->u.constant.f;
 				} else {
-					if (l->u.constant.f < 0 || l->u.constant.f > 0xffffffffffffffff)
+					if (l->u.constant.f < 0.0 || l->u.constant.f >= 0x1p64)
 						error(&tok.loc, "integer part of floating-point constant %g cannot be represented as unsigned integer", l->u.constant.f);
 					expr->u.constant.u = l->u.constant.f;
 				}