Security improvements

Improvements include
* adding additional build flags that warn about stack-smashing
and type conversion errors
* run-time checks for valid function input values and adquate
space for the result of arithmetic operations.
* make sure default case for switch statements do something
besides just assert
* disable using env. var. debugging in release mode

Change-Id: I5f048310c5c56e05d9ec31bcc273404d6a0dd646

src/rocm_smi_monitor.cc

@@ -224,6 +224,9 @@ static const std::map<const char *, monitor_depends_t> kMonFuncDependsMap = {
 
   Monitor::Monitor(std::string path, RocmSMI_env_vars const *e) :
                                                         path_(path), env_(e) {
+#ifdef NDEBUG
+    env_ = nullptr;
+#endif
 }
 Monitor::~Monitor(void) {
 }