Heap error in C

Question

I know this is really general, but I get "this" (see below) when I run my .c file in Visual C++ 2008 Express. It happens when I call malloc (). Take my work on this - I dynamically allocate memory properly.

HEAP[Code.exe]: HEAP: Free Heap block 211a10 modified at 211af8 after it was freed Windows has triggered a breakpoint in Code.exe.

This may be due to a corruption of the heap, which indicates a bug in Code.exe or any of the DLLs it has loaded.

This may also be due to the user pressing F12 while Code.exe has focus.

The output window may have more diagnostic information.

Why do I get this error? What does this even mean?

Answer 1

The error message tells you exactly why you got it:

Free Heap block 211a10 modified at 211af8 after it was freed

You had a heap allocated block that was freed then something wrote to that area of memory. It's not nice to write to a freed block of memory.