Question

I’ve got a structure as follows:

typedef struct {     std::wstring DevAgentVersion;     std::wstring SerialNumber;  } DeviceInfo; 

But when I try to use it I get all sorts of memory allocation errors.

If I try to pass it into a function like this:

GetDeviceInfo(DeviceInfo *info); 

I will get a runtime check error complaining that I didn’t initialize it before using it, which I seemed to have fixed with:

DeviceInfo *info = (DeviceInfo*)malloc(sizeof(DeviceInfo)); 

But then, in the function, when I try to set either of the structures stings, it complains that I’m trying to access a bad pointer when trying to set a value to the string.

What is the best way to initialize this structure (and all of it’s internal strings?

Answer 1

You should use new instead of malloc, to assure the constructor gets called for the DeviceInfo and its contained wstrings.

DeviceInfo *info = new DeviceInfo; 

In general, it’s best to avoid using malloc in C++.

Also, make sure to delete the pointer when you’re done using it.

Edit: Of course if you only need info in the local scope, you shouldn’t allocate it on the heap. Just do this instead:

DeviceInfo info; // constructed on the stack GetDeviceInfo( &info ); // pass the address of the info