harec

commit bbd01c3002170a72e7d82fdabd60dedd0cca9ae4
parent 87c077405904cd63f73c2b66a96b8a10defef19c
Author: Karl Schultheisz <k@kdsch.org>
Date:   Sat, 14 May 2022 22:00:00 -0400

eval: avoid float exception in compile-time exprs

Generate a diagnostic message for compile time expressions with a zero
divisor or modulus, which would cause a floating-point exception during
evaluation.

Signed-off-by: Karl Schultheisz <k@kdsch.org>

Diffstat:
M
src/eval.c
 | 
26
+++++++++++++++++++++++---

1 file changed, 23 insertions(+), 3 deletions(-)
diff --git a/src/eval.c b/src/eval.c
@@ -181,11 +181,23 @@ eval_binarithm(struct context *ctx, struct expression *in, struct expression *ou
 		break;
 	case BIN_DIV:
 		if (type_is_float(lvalue.result)) {
-			fval = ftrunc(lvalue.result, flval) / ftrunc(rvalue.result, frval);
+			double r = ftrunc(rvalue.result, frval);
+			if (r == 0) {
+				return EVAL_INVALID;
+			}
+			fval = ftrunc(lvalue.result, flval) / r;
 		} else if (type_is_signed(lvalue.result)) {
-			ival = itrunc(lvalue.result, ilval) / itrunc(rvalue.result, irval);
+			uintmax_t r = itrunc(rvalue.result, irval);
+			if (r == 0) {
+				return EVAL_INVALID;
+			}
+			ival = itrunc(lvalue.result, ilval) / r;
 		} else {
-			uval = itrunc(lvalue.result, ulval) / itrunc(rvalue.result, urval);
+			uintmax_t r = itrunc(rvalue.result, urval);
+			if (r == 0) {
+				return EVAL_INVALID;
+			}
+			uval = itrunc(lvalue.result, ulval) / r;
 		}
 		break;
 	case BIN_LSHIFT:
@@ -205,8 +217,16 @@ eval_binarithm(struct context *ctx, struct expression *in, struct expression *ou
 	case BIN_MODULO:
 		assert(!type_is_float(lvalue.result));
 		if (type_is_signed(lvalue.result)) {
+			uintmax_t r = itrunc(rvalue.result, irval);
+			if (r == 0) {
+				return EVAL_INVALID;
+			}
 			ival = itrunc(lvalue.result, ilval) % itrunc(rvalue.result, irval);
 		} else {
+			uintmax_t r = itrunc(rvalue.result, urval);
+			if (r == 0) {
+				return EVAL_INVALID;
+			}
 			uval = itrunc(lvalue.result, ulval) % itrunc(rvalue.result, urval);
 		}
 		break;