AVR Freaks

Well what it's doing is adding a call to the entry hook to the prologue of every function and a call to the exit hook to the epilogue. _delay_ms() works by being a function that can be completely optimised away but as soon as you add prologue/epilogue calls to it that optimisation presumably cannot occur.

 

But you wouldn't be leaving these instrumentation functions in your final code would you? Presumably this is just for testing coverage or something isn't it? Once you have proven 100% coverage you can switch it off for the real issue of the Release code can't you? In fact I'd be tempted to make the whole thing part of "Debug", maybe just building the hooks when either -DDEBUG or !(-DNDEBUG).

The way we used to do coverage was to have a header that effectively redefines { and } so that code such as:

void fn(int a, int b) {
    if (a > b) {
        PORTB = 0x55;
    }
}

(say) would become something like:

void fn(int a, int b) {
    enter(__FILE__, __FUNCTION__, __LINE__);
    if (a > b) {
        enter(__FILE__, __FUNCION__, __LINE__);
        PORTB = 0x55;
        leave(__FILE__, __FUNCTION__, __LINE__);
    }
    leave(__FILE__, __FUNCTION__, __LINE__);
}

and those functions just logged all the execution.

 

To be honest it wasn't quite this simplistic and I forget all the details. I know that each branch point actually involved having it's own incremented counter so it was also possible to say "it spent 31% of the time in fn()" etc. but the core idea is something like this.

 

I'm sure we weren't the first (or last) to think of doing something like this and I'm sure their must be authoritative articles about such ideas on the internet.

File, function, and line also appear in the source code for 'assert.h'.

http://www.nongnu.org/avr-libc/user-manual/assert_8h_source.html

 (line 104)

http://www.nongnu.org/avr-libc/user-manual/group__avr__assert.html#ga0041af519e0e7d47c9bcc83760c4669e

Would need to implement STDERR.

A very recent and short read (for a very difficult bug) :

Maximizing visibility through logging, as on Mars Pathfinder

by David Cummings

July 12, 2016

http://www.embedded.com/electronics-blogs/say-what-/4442366/Maximizing-visibility-through-logging--as-on-Mars-Pathfinder

 

Does not help mojo-chan.

The intent was to make visible that exceeding a constraint could cause an anomaly or an invalidity (stack overflow, equality operator instead of a relational operator, incorrect indexing, incorrect increment or decrement, overflow, underflow; some of those could cause an infinite loop caught by the watchdog).

 

Edit : last sentence