Fix UTF8 string length calculation (#2508)

Fixes #2451
Fixes #2452
Fixes #2453

Co-authored-by: Robert Fancsik <frobert@inf.u-szeged.hu>
JerryScript-DCO-1.0-Signed-off-by: Daniel Balla dballa@inf.u-szeged.hu

tests/jerry/regression-test-issue-2451.js

@@ -0,0 +1,19 @@
+// Copyright JS Foundation and other contributors, http://js.foundation
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+var src = "var a = 0; while(a) { switch(a) {" ;
+for (var i = 0; i < 4000; i++)
+    src += "-Infinity" + i + "\u00a0\u00a01.2e3";
+src += "\udc00%f0%90%80%80\udc00";
+print(src);

tests/jerry/regression-test-issue-2452.js

@@ -0,0 +1,19 @@
+// Copyright JS Foundation and other contributors, http://js.foundation
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+var src = "";
+for (var i = 0; i < 4000; i++)
+  src += "\udc00%f0%90%80%80\udc00";
+src += "} }";
+print(src);

tests/jerry/regression-test-issue-2453.js

@@ -0,0 +1,20 @@
+// Copyright JS Foundation and other contributors, http://js.foundation
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+var src = "";
+for (var i = 0; i < 4000; i++)
+  src += 4 + i + ": a += a += a; break; ";
+  src += "\𝔺\
+\
";
+print(src);