C++。 铸型 arrays 需要 memory 管理吗？

Question

The code looks like this:

std::string str = (char *) xmlTextReaderReadString(*xml);

Memory management for str works fine. str makes a deep copy of the character array.

What is being made when typecasting is what I am worried about. xmlTextReaderReadString is returning a typedefed unsigned char * or how they defined it an (xmlChar*).

I couldn't find a viable question on stack overflow, but if you did, just link it and I'll delete this post.

So forth with an example like this:

xmlTextReaderGetAttribute (*xml, (xmlChar*)"type"))

Do I need to memory manage the typecasted "type"

Answer 1

Yes, you need to call xmlFree() on the returned value from xmlTextReaderReadString , after building your std::string .

I never used that library, but a google search turned up the answer in seconds.

It also has nothing to do with the cast. You got a value, you can use it, but you need to free it afterward. If you use the value, in the meantime to build a std::string , the std::string will manage its own copy, you still need to manage yours.

The second API you use is also labelled

The string must be deallocated by the caller

but that applies to the returned value, not to "type" . This one is a literal that should not be freed.

http://www.mit.edu/afs.new/sipb/user/yoz/libxml2-2.7.3/doc/html/libxml-xmlreader.html