On Fri, 7 Mar 2008, Olin Lathrop wrote:

> sergio masci wrote:
> > It is far easier to
> > make a HLL program work even when it is a mess than it is to make an ASM
> > program work when it has an illusive bug.
> 
> I completely disagree.  A mess in any language is a mess, and worse than
> clean and well documented code in another language.

Unless the other language is ASM :-)

I have seen very big horrendous programs written in C that were easily 
fixed by compensating for a problem rather than fixing the underlying 
cause. You don't even need to take my word for it, just go and grab some 
opensource code (prefably a big project) that is at least 5 years old and 
still actively being "improved" by a lot of people. You will find that 
every so often someone will take it on themselves to re-write what has 
become a horrible mess and in the process produce a new package.

In ASM you can have the most wonderful, clean piece of code, yet a small 
illusive bug will bring it to it's knees. And finding that bug can be a 
real nightmare even for the person that wrote the code. In a lot of cases 
an experienced ASM programmer will get 99.99% of the code working properly 
very quickly and it's the last 0.01% that causes all the problems.

> 
> > Source level single stepping HLL code is a walk in the
> > park compared to single stepping ASM.
> 
> This is again completely contrary to my experience, at least with MPLAB,
> MPASM, and C18.  Debugging C18 with MPLAB is a very frustrating experience,
> whereas the MPLAB debugger works very nicely on MPASM code.

Modern high level debuggers make debugging C more like debugging 
interactive BASIC used to be. You can set watch points on *variables*, 
breakpoints on *statements*, conditions to look for. You can step through 
the source code one statement at a time and look at the consequences. 
There is no need to combine the values of seperate memory locations on 
paper to see what the value of a variable is, no need to try to decode 
stack relative locals yourself.

If you are having such a bad time debugging C18 programs I would suggest 
that the debugger is at fault.

Yes you can easily single step through machine code using something like 
MPLAB, but this is nothing like single stepping though source statements 
in a HLL. It requires far more time and great attention to the smallest 
detail - you're virtually running the simulation in your head and 
comparing it to what the program is actually doing. Let's be fair, 
it's a lot easier to simulate a single complex HLL statement in your head 
than the equivalent tens if not hundreds of ASM instructions :-)

I offten advise people NOT to try to learn to program in C on an MCU 
because it is far more difficult than learning on a PC.

Regards
Sergio
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