what is fsanitizer=address flag?
Usually C compiler doesn’t add boundaries check for memory access.
Sometimes due to code error, there is read or write from outside the buffer, such an error is usually hard to detect. Using this flag the compiler add some boundaries check, to ensure you won’t use a buffer to reach outside of its allocation.
what is heap-buffer-overflow?
use an array to reach after its allocation,
char* x = malloc(10);
char n=x[11]; //heap-buffer-overflow
(underflow is to reach before its allocation)
char* x = malloc(10);
char n=x[-11]; //heap-buffer-underflow
what is address and thread?
Address is position in memory, thread is part of process running sequence of code.
and why it says ‘read of size 1 at address..” ?
It means you read single byte form the given address.
I think your problem is that you allocate the BUFFER_SIZE for the buffer and read the same BUFFER_SIZE into it. The correct approach is to always declare at least one more byte than you read.
like this:
char* buff = malloc(BUFFER_SIZE+1);//notice to +1
fread(buff,1,BUFFER_SIZE,fp);