On 1/20/21 1:17 PM, David Brown wrote:
I /never/ use -O0, precisely because I find it absolutely terrible for
assembly level debugging. You can't see the wood for the trees, as all
local variables are on the stack, and even the simplest of C expressions
ends up with large numbers of assembly instructions. In my experience -
and this is obviously very subjective - using -O1 gives far more
readable assembly code while avoiding the kinds of code re-arrangement
and re-ordering of -O2 that makes assembly-level debugging difficult.
(-Og is an alternative for modern gcc versions, which can give most of
the speed of -O2 but is a little easier for debugging).
Interesting. My recollection is that -O0, regardless of variables being
on the stack, was more "linear": Each C statement was followed
more-or-less by the assembly code required to implement it, then the
next C statement and so on. In particular, variables in -O1 can get
tucked away into registers and "disappear" for long stretches of
assembly before popping up again, and the spaghetti-code jumping for
common code block elimination. Which is of course all good optimization,
but makes things hard to follow.
But I'll have to revisit the issue again.
Another major benefit of -O1 is that it enables much more code analysis,
which in turn enables much better static checking - I am a big fan of
warning flags and having the compiler tell me of likely problems before
I get as far as testing and debugging.
Me, too ("big fan").
(Your project here looks very interesting - I'm going to have a good
look at it when I get the chance. I won't be able to use it directly,
as a pure GPL license basically makes it unusable for anything but
learning or hobby use, but as it matches ideas I have had myself I am
interested in how it works.)
Thanks. Yes, it's basically a simple idea, and I found out recently that
others have attempted something similar (which I wish I'd known when I
started doing it myself). This is now very off-topic for this list, but
I'd like to get your input, including the GPL vs LPGPL issue (ironic
given that this is a GNU mailing list). Maybe open an issue at the
Github repository and we can discuss it there?
