"Compress" optimization level - Difficulties debug

jeffg28CLY · Joined: 24 Apr 2025 Posts: 6

Today I learned of #opt compress.
But the compiler manual says "Debugging with this level may be more difficult."

Difficult in what way? It doesn't elaborate on that.
So if I'd be using MPLAB X with CCS' C compiler and a Real Ice or ICD4 for debugging, is it going to maybe not step-through properly, or is it just going to be a bit sluggish? (not to say that MPLAB is anything approaching fast...) Or is it only difficult to debug if I'm working with assembly code?

Ttelmah · Joined: 11 Mar 2010 Posts: 19826

The point is that with high opt levels parts of routines may be reused
inside other routines. So the debug will suddenly jump into parts of code
that are nothing to do with what you are trying to debug. You can always
switch to debugging at the assembler level, and then things are OK, but
stepping through C code may be very random, when hish levels are used.