[SYCL] Add validation + exception handling to SYCL_PARALLEL_FOR_RANGE_ROUNDING_PARAMS

sycl/source/detail/config.hpp

@@ -205,29 +205,51 @@ template <> class SYCLConfig<SYCL_PARALLEL_FOR_RANGE_ROUNDING_PARAMS> {
       return;
 
     static bool ProcessedFactors = false;
+    static bool FactorsAreValid = false;
     static size_t MF;
     static size_t GF;
     static size_t MR;
     if (!ProcessedFactors) {
+      auto GuardedStoi = [](size_t &val, const std::string &str) {
+        try {
+          val = std::stoi(str);
+          return true;
+        // Ignore parsing exceptions, but throw on unexpected exceptions:
+        } catch (const std::invalid_argument&) {
+        } catch (const std::out_of_range&) {
+        }
+        return false;
+      };
+
       // Parse optional parameters of this form (all values required):
       // MinRound:PreferredRound:MinRange
       std::string Params(RoundParams);
       size_t Pos = Params.find(':');
-      if (Pos != std::string::npos) {
-        MF = std::stoi(Params.substr(0, Pos));
+      if (Pos != std::string::npos &&
+          GuardedStoi(MF, Params.substr(0, Pos)) && MF > 0) {
         Params.erase(0, Pos + 1);
         Pos = Params.find(':');
-        if (Pos != std::string::npos) {
-          GF = std::stoi(Params.substr(0, Pos));
+        if (Pos != std::string::npos &&
+            GuardedStoi(GF, Params.substr(0, Pos)) && GF > 0) {
           Params.erase(0, Pos + 1);
-          MR = std::stoi(Params);
+          // Factors are valid only if all parsed successfully:
+          FactorsAreValid = GuardedStoi(MR, Params);
+          // Note that MinRange = 0 is considered valid.
         }
       }
       ProcessedFactors = true;
     }
-    MinFactor = MF;
-    GoodFactor = GF;
-    MinRange = MR;
+    if (FactorsAreValid) {
+      MinFactor = MF;
+      GoodFactor = GF;
+      MinRange = MR;
+    } else {
+      std::cerr
+          << "WARNING: Invalid value passed for "
+          << "SYCL_PARALLEL_FOR_RANGE_ROUNDING_PARAMS (Expected format "
+          << "MinRound:PreferredRound:MinRange, where MinRound, PreferredRound"
+          << " > 0). Provided parameters will be ignored." << std::endl;
+    }
   }
 };