Assignment of string to structure element

Question

My program crashes when I try to assign a string value to a member of a structure. My suspicion is that the member (of type string) within the structure was never properly alloc

Answer 1

The way you are allocating node is incorrect: if you want to dynamically allocate non-POD types in C++, you need to use new, since it will call the required constructors (followed by a call to delete when appropriate).

But it might be simpler to allocate an automatic instance:

DataRow node;

If you do need a pointer, make sure to have a look at smart pointers, particularly std::unique_ptr and std::shared_ptr. See also boost::scoped_ptr.

Answer 2

You have to create a new struct and not use malloc at all.

So use:

DataRow* node = new DataRow;

you should also take care of cleaning it up like so:

delete node;

and in case you don't want to allocate it from the heap you can do this as well:

DataRow node;

Answer 3

In C++ use 'new' instead of 'malloc'. Using malloc does not run the constructor of your class, so the string is not initialized.

Answer 4

malloc doesn't ensure any constructors of the members of your struct are called. In C++ struct is basically the same as class, the only difference is that members are public by default rather than private. So you should new the object/struct, and delete it when done.

Answer 5

So before I get to answering your question I just wanted to say that you should not use Malloc in c++ unless you are forced to. This answer explains why fairly well.

In what cases do I use malloc vs new?

With that said changing this line

DataRow* node = (DataRow*)malloc(sizeof(DataRow));

To this

DataRow* node = new DataRow;

Will fix your problem