Why is running attached to the debugger so slow?

Question

What is going on that causes a debug build to be so much slower attached to the debugger compared to unattached? They are both the same exe running.

Edit: Most of th

Answer 1

If your debugger uses software watchpoints it internally step executes the code and checks these points and changes in variable values.

The [VS] debugger can only support 4 hardware data breakpoints. If you use expressions (a + b), debugger uses emulation mode.

Also, loading debugging information for libraries is slower and it contributes to the perceived execution time (response time).

Reference