check integer overflow for multiplication before realloc

dmenu.c

@@ -1,6 +1,7 @@
 /* See LICENSE file for copyright and license details. */
 #include <ctype.h>
 #include <locale.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -556,6 +557,8 @@ readstdin(void)
 	for (i = 0; (len = getline(&line, &linesiz, stdin)) != -1; i++) {
 		if (i + 1 >= itemsiz) {
 			itemsiz += 256;
+			if (itemsiz > SIZE_MAX / sizeof(*items))
+				die("too many items");
 			if (!(items = realloc(items, itemsiz * sizeof(*items))))
 				die("cannot realloc %zu bytes:", itemsiz * sizeof(*items));
 		}