Same address but different string - c++

Question

Below results show two same string pointer have different value.
Why?
v8::String::Utf8Value just gives its string member, see https://v8docs.nodesource.com/node-0.8/d4/da0/v8_8h_source.html#l01286
#include <nan.h>
#include <string>
NAN_METHOD(Print) {
Nan::MaybeLocal<v8::String> maybeString = Nan::To<v8::String>(info[0]);
if (maybeString.IsEmpty() == false) {
v8::Local<v8::String> str = maybeString.ToLocalChecked();
char *ptr = *v8::String::Utf8Value(info.GetIsolate(), str);
printf("string %s\n", *v8::String::Utf8Value(info.GetIsolate(), str));
printf(" %s\n", ptr);
printf("ptr %p\n", *v8::String::Utf8Value(info.GetIsolate(), str));
printf(" %p\n", ptr);
printf("ptr %p\n", (char *)*v8::String::Utf8Value(info.GetIsolate(), str));
printf(" %p\n", (char *)ptr);
printf("string %s\n", (char *)*v8::String::Utf8Value(info.GetIsolate(), str));
printf(" %s\n", (char *)ptr);
}
}
NAN_MODULE_INIT(Init) {
Nan::Set(target, Nan::New("print").ToLocalChecked(),
Nan::GetFunction(Nan::New<v8::FunctionTemplate>(Print)).ToLocalChecked());
}
NODE_MODULE(myaddon, Init);
Result of info[0]='hello world':
string hello world
�AZ
ptr 0x65a4140
0x65a4140
ptr 0x65a4140
0x65a4140
string hello world
�AZ

Answer 1

printf("string %s\n", *v8::String::Utf8Value(info.GetIsolate(), str));
Here, you create a new object of type v8::String::Utf8Value. It's a temporary object. As soon as this statement completes, it will no longer exist. This is fine, but this is not:
char *ptr = *v8::String::Utf8Value(info.GetIsolate(), str);
printf(" %s\n", ptr);
After the first line of code executes, the v8::String::Utf8Value no longer exists. So the ptr doesn't point to anything. (If you think it does, explain how you would free the memory it points to.) So you can't access it later, but your printf does.