Fix a crash

Author: Szelethus

clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp

@@ -461,12 +461,14 @@ ProgramStateRef CStringChecker::checkInit(CheckerContext &C,
   const QualType ElemTy = Ctx.getBaseElementType(SuperR->getValueType());
   const NonLoc Zero = SVB.makeZeroArrayIndex();
 
-  Loc FirstElementVal =
-      State->getLValue(ElemTy, Zero, loc::MemRegionVal(SuperR)).castAs<Loc>();
+  std::optional<Loc> FirstElementVal =
+      State->getLValue(ElemTy, Zero, loc::MemRegionVal(SuperR)).getAs<Loc>();
+  if (!FirstElementVal)
+    return State;
 
   // Ensure that we wouldn't read uninitialized value.
   if (Filter.CheckCStringUninitializedRead &&
-      State->getSVal(FirstElementVal.castAs<Loc>()).isUndef()) {
+      State->getSVal(*FirstElementVal).isUndef()) {
     llvm::SmallString<258> Buf;
     llvm::raw_svector_ostream OS(Buf);
     OS << "The first element of the ";

clang/test/Analysis/bstring_UninitRead.c

@@ -122,3 +122,11 @@ void ga_copy_strings() {
     memmove(alloc, ((char **)ga_copy_strings_from_0)[i], 1);
 }
 
+// Creduced crash. In this case, retrieving the Loc for the first element failed.
+char mov_mdhd_language_map[][4] = {};
+int ff_mov_lang_to_iso639_code;
+char *ff_mov_lang_to_iso639_to;
+void ff_mov_lang_to_iso639() {
+  memcpy(ff_mov_lang_to_iso639_to,
+         mov_mdhd_language_map[ff_mov_lang_to_iso639_code], 4);
+}