Avoid memory access errors with 4-chars context ids (#250)

For a 4-chars CTXID, i.e. one that does not include a null character,
the strlen() calls were happily accessing memory until they eventually
encountered a null character somewhere in memory.

This was detected by valgrind, which reported a memory error when
using a CTXID such as "INTM":

==21924== Conditional jump or move depends on uninitialised value(s)
==21924==    at 0x4C30F78: strlen (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==21924==    by 0x4E4B5A0: dlt_print_id (dlt_common.c:303)
==21924==    by 0x4E4CF47: dlt_message_header_flags (dlt_common.c:687)
==21924==    by 0x4E51434: dlt_message_print_ascii (dlt_common.c:3169)
==21924==    by 0x4E4247A: dlt_user_print_msg (dlt_user.c:4108)
==21924==    by 0x4E46D92: dlt_user_log_send_log (dlt_user.c:3670)
==21924==    by 0x4E46F14: dlt_user_log_write_finish (dlt_user.c:1611)

Sanitize some code

Using memset() and memcpy() is always preferable to hand-rolled loops,
because compilers have built-in support for them.

Signed-off-by: Martin Willers <M.Willers@gmx.net>

1 files changed, 15 insertions, 8 deletions

diff --git a/src/shared/dlt_common.c b/src/shared/dlt_common.c
index 2ff3775..254f4ce 100644
--- a/src/shared/dlt_common.c
+++ b/src/shared/dlt_common.c
@@ -286,25 +286,32 @@ DltReturnValue dlt_print_char_string(char **text, int textlength, uint8_t *ptr,
     return DLT_RETURN_OK;
 }
 
+size_t dlt_strnlen_s(const char* str, size_t maxsize)
+{
+    if (str == NULL)
+        return 0;
+
+    for (size_t i = 0; i < maxsize; ++i) {
+        if (str[i] == '\0')
+            return i;
+    }
+    return maxsize;
+}
+
 void dlt_print_id(char *text, const char *id)
 {
     /* check nullpointer */
     if ((text == NULL) || (id == NULL))
         return;
 
-    int i, len;
-
     /* Initialize text */
-    for (i = 0; i < DLT_ID_SIZE; i++)
-        text[i] = '-';
+    memset(text, '-', DLT_ID_SIZE);
 
     text[DLT_ID_SIZE] = 0;
 
-    len = ((strlen(id) <= DLT_ID_SIZE) ? strlen(id) : DLT_ID_SIZE);
+    size_t len = dlt_strnlen_s(id, DLT_ID_SIZE);
 
-    /* Check id*/
-    for (i = 0; i < len; i++)
-        text[i] = id[i];
+    memcpy(text, id, len);
 }
 
 void dlt_set_id(char *id, const char *text)