heap corruption

[birbal]

Works
char* lastStr=new char[strlen(this->data)+strlen(st2.data)+1];
delete[] lastStr; //delete dynamically allocated char array


Does not work. shows heap corruption
char* lastStr=new char[strlen(this->data)+strlen(st2.data)];
delete[] lastStr; //delete dynamically allocated char array

Why is it happening? and also what is best way to debug heap corruption or any runtime error?

[long double main]

Do you have any code between those two lines?

This code should not crash, assuming that your strings end in null characters:

char* lastStr=new char[strlen(this->data)+strlen(st2.data)];
delete[] lastStr; //delete dynamically allocated char array 

But this might:

char* lastStr=new char[strlen(this->data)+strlen(st2.data)];
strcpy(lastStr, this->data);
strcat(lastStr, st2.data);
delete[] lastStr;

Remember that you need space for the terminating null character in a C string.

[birbal]

you are exactly right, i have copy and concat function between this. I dont understand why it happens only it tries to free the memory not when the functions are operating. can you explain how internally this causing heap corruption?