[coreboot-gerrit] Change in coreboot[master]: utils/kconfig/nconf.c: Fix truncation warning in `item_add_str`

[Jude Rich (Code Review)]

Jude Rich has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/37939 )

Change subject: utils/kconfig/nconf.c: Fix truncation warning in `item_add_str`
......................................................................

utils/kconfig/nconf.c: Fix truncation warning in `item_add_str`

While appending a string in `item_add_str`, there is a warning about truncating
the string to 256 bytes due to unnecessary buffering. By removing the buffering
and writing directly to the string, the warning is vanquished.

Signed-off-by: Jude A Rich 
Change-Id: Idb2dfad7e401954f4bb83d0409ab71dcd7277f47
---
M util/kconfig/nconf.c
1 file changed, 18 insertions(+), 17 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/39/37939/1

diff --git a/util/kconfig/nconf.c b/util/kconfig/nconf.c
index 905dcd1..4181c41 100644
--- a/util/kconfig/nconf.c
+++ b/util/kconfig/nconf.c
@@ -561,32 +561,33 @@
    curses_menu_items[items_num] = NULL;
 }

-/* very hackish. adds a string to the last item added */
+/* add a string to the last item added */
 static void item_add_str(const char *fmt, ...)
 {
    va_list ap;
-	int index = items_num-1;
-	char new_str[256];
-	char tmp_str[256];
+	char *append_ptr; /* pointer to the free space in the target string */
+	int index = items_num-1; /* index of item to append string */
+	int kmi_str_len; /* length of initial string */
+	int str_space; /* length of unused space in string */

+	/* return if there's no item to work with */
    if (index < 0)
    	return;

-	va_start(ap, fmt);
-	vsnprintf(new_str, sizeof(new_str), fmt, ap);
-	va_end(ap);
-	snprintf(tmp_str, sizeof(tmp_str), "%s%s",
-			k_menu_items[index].str, new_str);
-	strncpy(k_menu_items[index].str,
-		tmp_str,
-		sizeof(k_menu_items[index].str));
+	kmi_str_len = strlen(k_menu_items[index].str);
+	str_space = sizeof(k_menu_items[index].str) - kmi_str_len;
+	append_ptr = k_menu_items[index].str + kmi_str_len;

+	/* append the string */
+	va_start(ap, fmt);
+	vsnprintf(append_ptr, str_space, fmt, ap);
+	va_end(ap);
+
+	/* set menu item to new item string */
    free_item(curses_menu_items[index]);
-	curses_menu_items[index] = new_item(
-			k_menu_items[index].str,
-			k_menu_items[index].str);
-	set_item_userptr(curses_menu_items[index],
-			&k_menu_items[index]);
+	curses_menu_items[index] = new_item(k_menu_items[index].str,
+	    k_menu_items[index].str);
+	set_item_userptr(curses_menu_items[index], &k_menu_items[index]);
 }

/* get the tag of the currently selected item */