internal-logging: Fix issues with file logging (#378)

This commit fixes the following issues if access
to the internal log file is not possible (logging_mode = DLT_LOG_TO_FILE)
* dlt_log_free tried to call fclose on a nullptr
  Added a nullcheck for this
* Access to log file might be denied but access to logs is still wanted
  Add a new CMake option WITH_DLT_FILE_LOGGING_SYSLOG_FALLBACK
  If this is set to ON and the logging moe is set to file,
  the dlt-daemon will fall back to syslog if opening the internal log
  file failed

Signed-off-by: Alexander Mohr <alexander.m.mohr@mercedes-benz.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/src/shared/dlt_common.c b/src/shared/dlt_common.c
index adda5db..57455fa 100644
--- a/src/shared/dlt_common.c
+++ b/src/shared/dlt_common.c
@@ -1814,11 +1814,11 @@ void dlt_print_with_attributes(bool state)
     print_with_attributes = state;
 }
 
-void dlt_log_init(int mode)
+DltReturnValue dlt_log_init(int mode)
 {
     if ((mode < DLT_LOG_TO_CONSOLE) || (mode > DLT_LOG_DROPPED)) {
         dlt_vlog(LOG_WARNING, "Wrong parameter for mode: %d\n", mode);
-        return;
+        return DLT_RETURN_WRONG_PARAMETER;
     }
 
     logging_mode = mode;
@@ -1829,14 +1829,16 @@ void dlt_log_init(int mode)
 
         if (logging_handle == NULL) {
             dlt_user_printf("Internal log file %s cannot be opened!\n", logging_filename);
-            return;
+            return DLT_RETURN_ERROR;
         }
     }
+
+    return DLT_RETURN_OK;
 }
 
 void dlt_log_free(void)
 {
-    if (logging_mode == DLT_LOG_TO_FILE)
+    if (logging_mode == DLT_LOG_TO_FILE && logging_handle)
         fclose(logging_handle);
 }