Does delete[] deallocate the entire block of memory?

Question

Consider the following:

char* msg = new char[20]; 
msg[4] = '\0'; 
delete[] msg; 

1. Did the delete[] msg deallocate all the 20 chars allocated for msg or just those up to the \0?
2. If it deallocated only up to the \0, how can I force it to delete the entire block of memory?

Answer 1

The original code in your question had undefined behaviour, since you were using delete with new[].

I notice that you have fixed it by replacing the delete with delete[]:

delete[] msg;

This is correct, and will deallocate all memory that's been allocated by new[].

There is no concept of "deleting till \0", or any other such "partial" deletion. Only complete blocks allocated with new/new[] can be deleted, so your code is fine.