c++ – Error: free(): invalid next size (fast):

c++ – Error: free(): invalid next size (fast):

It means that you have a memory error. You may be trying to free a pointer that wasnt allocated by malloc (or delete an object that wasnt created by new) or you may be trying to free/delete such an object more than once. You may be overflowing a buffer or otherwise writing to memory to which you shouldnt be writing, causing heap corruption.

Any number of programming errors can cause this problem. You need to use a debugger, get a backtrace, and see what your program is doing when the error occurs. If that fails and you determine you have corrupted the heap at some previous point in time, you may be in for some painful debugging (it may not be too painful if the project is small enough that you can tackle it piece by piece).

I encountered the same problem, even though I did not make any dynamic memory allocation in my program, but I was accessing a vectors index without allocating memory for it.
So, if the same case, better allocate some memory using resize() and then access vector elements.

c++ – Error: free(): invalid next size (fast):

We need the code, but that usually pops up when you try to free() memory from a pointer that is not allocated. This often happens when youre double-freeing.