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, 43 insertions, 0 deletions

diff --git a/tests/gtest_dlt_common.cpp b/tests/gtest_dlt_common.cpp
index adbc87d..9afb830 100644
--- a/tests/gtest_dlt_common.cpp
+++ b/tests/gtest_dlt_common.cpp
@@ -4067,6 +4067,49 @@ TEST(t_dlt_print_char_string, nullpointer)
 
 
 
+/* Begin Method:dlt_common::dlt_strnlen_s*/
+TEST(t_dlt_strnlen_s, nullpointer)
+{
+    size_t len = dlt_strnlen_s(NULL, 0);
+    EXPECT_EQ(len, 0);
+}
+
+TEST(t_dlt_strnlen_s, len_zero)
+{
+    const char text[] = "The Quick Brown Fox";
+
+    size_t len = dlt_strnlen_s(text, 0);
+    EXPECT_EQ(len, 0);
+}
+
+TEST(t_dlt_strnlen_s, len_smaller)
+{
+    const char text[] = "The Quick Brown Fox";
+
+    size_t len = dlt_strnlen_s(text, 10);
+    EXPECT_EQ(len, 10);
+}
+
+TEST(t_dlt_strnlen_s, len_equal)
+{
+    const char text[] = "The Quick Brown Fox";
+
+    size_t len = dlt_strnlen_s(text, 19);
+    EXPECT_EQ(len, 19);
+}
+
+TEST(t_dlt_strnlen_s, len_larger)
+{
+    const char text[] = "The Quick Brown Fox";
+
+    size_t len = dlt_strnlen_s(text, 100);
+    EXPECT_EQ(len, 19);
+}
+/* End Method:dlt_common::dlt_strnlen_s*/
+
+
+
+
 /* Begin Method:dlt_common::dlt_print_id */
 TEST(t_dlt_print_id, normal)
 {