From fd4bd4dabe8011b016e3f8e6c3de5cfe6bc1f41d Mon Sep 17 00:00:00 2001
From: Danny Holman <dholman@gymli.xyz>
Date: Wed, 20 Jan 2021 22:47:46 -0600
Subject: kernel: iterate over string with index

Iterate over a formatted string with an index and strlen instead of
using a non-const pointer. The latter method may result in unsafe memory
conditions.

Signed-off-by: Danny Holman <dholman@gymli.xyz>
---
 kernel/io.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/kernel/io.c b/kernel/io.c
index ca787b3..e2bef20 100644
--- a/kernel/io.c
+++ b/kernel/io.c
@@ -1,5 +1,6 @@
 #include <kernel/io.h>
 #include <kernel/string.h>
+#include <kernel/tty.h>
 
 char* convert(unsigned int num, int base) {
         static char rep[] = "0123456789ABCDEF";
@@ -18,19 +19,18 @@ char* convert(unsigned int num, int base) {
 }
 
 int vprintf(const char *fmt, va_list args) {
-        char *traverse;
         char *s;
         int i;
 
-        for (traverse = fmt; *traverse != '\0'; traverse++) {
-                if (*traverse != '%') {
-                        tty_putchar(*traverse);
+        for (size_t n = 0; n < strlen(fmt); n++) {
+                if (fmt[n] != '%') {
+                        tty_putchar(fmt[n]);
                         continue;
                 } else {
-                        traverse++;
+                        n++;
                 }
 
-                switch (*traverse) {
+                switch (fmt[n]) {
                         case 'c':
                                 i = va_arg(args, int);
                                 tty_putchar(i);
-- 
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