Re: [avrdude-dev] [bug #44717] avrdude creates empty flash dump

[Joerg Wunsch]

As D wrote:

> Now I see that the guy who invented this feature was trying to save
> some space on his HDD but it is not polite to program in such a way.

Actually, it started out as a feature/enhancement request, initially
only applied to the S-Record output routines (SVN r330), but then
generalized (SVN r331), back in 2003.

No, I don't think saving disk space was the major issue there.  It's
rather that most people simple are not interested in seeing those
bytes at all, as they don't carry any information – these days, where
controllers with 128 and more KiB of flash are pretty standard, even
more than 12 years ago when it was introduced.  If you have an
ATxmega256* filled with just 1 KiB, and read it back, you'll have a
hard time spotting your actual flash data in the lengthy file.

> I waste about 2 days to discover this undocumented feature

I agree that it being not documented is a bug.

Besides of documenting it properly, what do you think about issuing a
warning message in case the readout yielded no non-0xFF flash data,
and thus results in an empty file?

> if you do read and then just make verify then avrdude will crash with
> divided by zero "feature"... :)

That's been another bug, but one that has already been fixed since:

https://savannah.nongnu.org/bugs/?40142

Just to make sure:

$ ./avrdude -c stk500v2 -P /dev/cuaU2 -p m16 -U fl:v:foo.bin:r

avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.01s

avrdude: Device signature = 0x1e9403 (probably m16)
avrdude: verifying flash memory against foo.bin:
avrdude: load data flash data from input file foo.bin:
avrdude: input file foo.bin contains 0 bytes
avrdude: reading on-chip flash data:

Reading | ################################################## | 100% 0.00s

avrdude: verifying ...
avrdude: 0 bytes of flash verified

avrdude done.  Thank you.

> PS: Nobody(Google, Yandex) knows about this feature by the way.... heck...
> time wasted...

It's probably hard to find the correct keywords for search
engines to find about this.

пока,
-- 
cheers, Joerg               .-.-.   --... ...--   -.. .  DL8DTL

http://www.sax.de/~joerg/
Never trust an operating system you don't have sources for. ;-)