harec

commit a347ffcb11f2194ebd42889f586c0d4d8095ab59
parent 29f272f8b1cb52a0b310a82dabf450b6eddaafba
Author: Karl Schultheisz <k@kdsch.org>
Date:   Tue, 17 May 2022 09:31:56 -0400

eval: avoid integer div-by-0 in compile-time expr

Generate a diagnostic message for integer-typed compile-time
expressions with a zero divisor or modulus, which would raise SIGFPE
during evaluation.

A previous patch (now reverted) should not have forbade these
operations for floats, which (in the default floating-point
environment) raise no signal.

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

Diffstat:
M
src/eval.c
 | 
20
++++++++++++++++++--

1 file changed, 18 insertions(+), 2 deletions(-)
diff --git a/src/eval.c b/src/eval.c
@@ -183,9 +183,17 @@ eval_binarithm(struct context *ctx, struct expression *in, struct expression *ou
 		if (type_is_float(lvalue.result)) {
 			fval = ftrunc(lvalue.result, flval) / ftrunc(rvalue.result, frval);
 		} 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 +213,16 @@ 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;