Fix uninitialized memory

clang/lib/Driver/SanitizerArgs.cpp

@@ -1561,6 +1561,9 @@ SanitizerMask parseArgCutoffs(const Driver &D, const llvm::opt::Arg *A,
 
     SanitizerMask Kind;
     for (unsigned int i = 0; i < SanitizerKind::SO_Count; i++) {
+      // Invoking bitPosToMask repeatedly is inefficient: we could simply
+      // repeatedly set the LSB then left-shift; however, we assume the
+      // compiler will optimize this (in any case, the runtime is negligible).
       if (Cutoffs[i])
         Kind |= SanitizerMask::bitPosToMask(i);
     }

clang/lib/Frontend/CompilerInvocation.cpp

@@ -1439,7 +1439,7 @@ static SmallVector<StringRef, 4> serializeSanitizerKinds(SanitizerSet S) {
 static SanitizerMaskCutoffs parseSanitizerWeightedKinds(
     StringRef FlagName, const std::vector<std::string> &Sanitizers,
     DiagnosticsEngine &Diags) {
-  SanitizerMaskCutoffs Cutoffs;
+  SanitizerMaskCutoffs Cutoffs = {0};
   for (const auto &Sanitizer : Sanitizers) {
     if (!parseSanitizerWeightedValue(Sanitizer, /*AllowGroups=*/false, Cutoffs))
       Diags.Report(diag::err_drv_invalid_value) << FlagName << Sanitizer;