Merge pull request 'bugfix and changelog for Linux getUptime' (#745) from eive/fsfw:important_bugfix_linux_get_uptime into development

Reviewed-on: fsfw/fsfw#745

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## Fixes
 
+- Linux OSAL `getUptime` fix: Check validity of `/proc/uptime` file before reading uptime.
 - PUS Health Service: Size check for set health command.
 - PUS Health Service: Perform operation completion for announce health command.
 

src/fsfw/osal/linux/Clock.cpp

@@ -76,14 +76,17 @@ timeval Clock::getUptime() {
 }
 
 ReturnValue_t Clock::getUptime(timeval* uptime) {
-  // TODO This is not posix compatible and delivers only seconds precision
-  //  Linux specific file read but more precise.
   double uptimeSeconds;
-  if (std::ifstream("/proc/uptime", std::ios::in) >> uptimeSeconds) {
+  std::ifstream ifile("/proc/uptime");
+  if (ifile.bad()) {
+    return returnvalue::FAILED;
+  }
+  if (ifile >> uptimeSeconds) {
     uptime->tv_sec = uptimeSeconds;
     uptime->tv_usec = uptimeSeconds * (double)1e6 - (uptime->tv_sec * 1e6);
+    return returnvalue::OK;
   }
-  return returnvalue::OK;
+  return returnvalue::FAILED;
 }
 
 // Wait for new FSFW Clock function delivering seconds uptime.