Re: Extended Hamming encode/decode

On Sun, 07 Mar 2010 20:58:59 -0700, D Yuniskis
<not.going.to.be@xxxxxxxx> wrote:

steve_schefter@xxxxxxxxxxx wrote:
David Brown <david.br...@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

To use LGPL'ed code with your own code, anyone receiving your code must
have access to the LGPL'ed code, be able to change and recompile that
code, then link it along with the rest of the binary and run that
software instead. For non-embedded systems (or "big" embedded systems),
that typically means the LGPL'ed code is part of a dynamic library. To
use LGPL code in a (typically statically linked) embedded system means
that the end user will need access to your source code, or at least
compiled and linkable object files. Since that is impractical or
impossible for most embedded systems, the rough conclusion is that pure
LGPL code is very seldom suitable for embedded systems.

Okay, thanks. I guess where we differ is in the opinion that
dynamically linked apps are not suitable for embedded systems. The
ones I work on (Linux-based) tend to use dynamically linked apps more
than statically linked ones. In the early days, I've even had to
force the apps to be dynamically linked to fit everything in flash
(several apps linked with the same library).

I think the reasons many (most?) embedded systems shy away from
"shared objects" are twofold: resources and tools.

Small (< 1MB TEXT+DATA) systems

"Modest," for me, is 512 flash and 16 RAM. "Small" would be
half that. "Decent" and kind of roomy is anything like 4k
flash and 512 RAM. "Unbelievably big" is 40k flash and 4k
RAM.

Anywhere _near_ 1Mb of anything is called "monstrously huge,"
or is just a "workstation" and has way way too many pins or
is way too expensive or is way too power hungry or has way
too many extras to worry about. Probably all of those.

My operating system, which supports pre-emption or
cooperative tasking (either), and messages and sleep and
semaphore queues and so on can live with singly-linked lists
(everything is compile-time selectable, so you can remove
what you don't want or add what you do) for the queues. It
adds a little extra code and certainly some small execution
time, but sometimes you want that because RAM is scarse. I
can shovel it into very small devices. But the nice thing is
that when I have the RAM for doubly-linked lists, it's just a
change to a #define and then a recompile. Or if I want to
support a lot of processes, etc. It's all compile-time
stuff.

tend to feel like they don't
have the resources to spare on the dynamic binding (I think
this is usually silly-talk but the folks building those
systems are the ones who have the final say :> ). Personally,
I find the overhead to be small and the discipline associated
with developing with s.o.'s makes it a *big* win "almost always".

Well, if you consider <1Mb to be 'small,' then most
certainly.

Despite your earlier agreement with me on some points, we do
not appear to live in similar programming worlds.

The other reason is often poor tools. E.g., you aren't going to
find (?) an 8051 compiler/linkage editor that will support
this sort of thing. So, to do it, you (the developer) have to
build your own tools (this isn't very hard but *is* another
step and something *you* have to support -- not the tool vendor).

I've had to develop my own linkers before. Twice, at least.
It happens. You just don't want to make it happen if you can
avoid it.

I think if more folks were accustomed to this sort of
run-time environment, they might be more willing to
add it to their toolkit (e.g., just like adding PMMU
support)

Not sure what to say to that. I understand some of the
context, but not all of it, I suspect.

Jon
.

Relevant Pages

  • Re: Extended Hamming encode/decode
    ... have access to the LGPL'ed code, be able to change and recompile that ... LGPL code is very seldom suitable for embedded systems. ... dynamically linked apps are not suitable for embedded systems. ...
    (comp.arch.embedded)
  • Re: Extended Hamming encode/decode
    ... LGPL code is very seldom suitable for embedded systems. ... dynamically linked apps are not suitable for embedded systems. ... (everything is compile-time selectable, so you can remove ... but sometimes you want that because RAM is scarse. ...
    (comp.arch.embedded)
  • Re: Extended Hamming encode/decode
    ... have access to the LGPL'ed code, be able to change and recompile that ... LGPL code is very seldom suitable for embedded systems. ... dynamically linked apps are not suitable for embedded systems. ...
    (comp.arch.embedded)
  • Re: What are my options for dictionary hashing?
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  • Re: Extended Hamming encode/decode
    ... LGPL code is very seldom suitable for embedded systems. ... dynamically linked apps are not suitable for embedded systems. ... find an 8051 compiler/linkage editor that will support ... this sort of thing. ...
    (comp.arch.embedded)