fix SIGFPE caused by signed division overflow

Avoid evaluating INT_MIN / -1 and INT_MIN % -1, which will trap on x86
and crash sparse.

Signed-off-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Christopher Li <sparse@chrisli.org>

expand.c

@@ -239,6 +239,8 @@ static int simplify_int_binop(struct expression *expr, struct symbol *ctype)
 	case SIGNED('%'):
 		if (!r)
 			goto Div;
+		if (l == mask && sr == -1)
+			goto Overflow;
 		v = sl % sr;
 		break;
 

simplify.c

@@ -406,6 +406,8 @@ static int simplify_constant_binop(struct instruction *insn)
 	case OP_DIVS:
 		if (!right)
 			return 0;
+		if (left == mask && right == -1)
+			return 0;
 		res = left / right;
 		break;
 	case OP_MODU:
@@ -416,6 +418,8 @@ static int simplify_constant_binop(struct instruction *insn)
 	case OP_MODS:
 		if (!right)
 			return 0;
+		if (left == mask && right == -1)
+			return 0;
 		res = left % right;
 		break;
 	case OP_SHL:

validation/div.c

@@ -0,0 +1,29 @@
+#include <limits.h>
+
+static int xd = 1 / 0;
+static int xl = 1L / 0;
+static int xll = 1LL / 0;
+
+static int yd = INT_MIN / -1;
+static long yl = LONG_MIN / -1;
+static long long yll = LLONG_MIN / -1;
+
+static int zd = INT_MIN % -1;
+static long zl = LONG_MIN % -1;
+static long long zll = LLONG_MIN % -1;
+
+/*
+ * check-name: division constants
+ *
+ * check-error-start
+div.c:3:19: warning: division by zero
+div.c:4:20: warning: division by zero
+div.c:5:22: warning: division by zero
+div.c:7:25: warning: constant integer operation overflow
+div.c:8:27: warning: constant integer operation overflow
+div.c:9:34: warning: constant integer operation overflow
+div.c:11:25: warning: constant integer operation overflow
+div.c:12:27: warning: constant integer operation overflow
+div.c:13:34: warning: constant integer operation overflow
+ * check-error-end
+ */