RFC : Heap management using TLSF

Joel Sherrill joel.sherrill at OARcorp.com
Wed Jul 23 18:42:14 UTC 2008

Keith Robertson wrote:
> Joel Sherrill wrote:
>> Keith Robertson wrote:
>>> Chris Caudle wrote:
>>>> Is LGPL compatible to ship with the GPL-plus-exceptions license of
>>>> RTEMS?
>>>> I have to admit, I'm not quite clear on what the difference is between
>>>> RTEMS variant of GPL and LGPL, or why RTEMS did not use LGPL.  Is it
>>>> historical, e.g. LGPL did not exist at the time the decision was made?
>>> I seem to recall that a member of the list (possibly Pavel?) knew the
>>> author of TLSF and thought that if there was a licensing problem, the
>>> author may be willing to relicense it under an rtems compatible license.
>> This is true.
>>> As an aside, I too would be interested to understand the difference
>>> between LGPL and GPL + rtems exception.
>> The RTEMS exception does not place any restrictions on
>> the user's application.
>> When applications are statically linked, the LGPL requires
>> that (as a minimum) you provide your closed source code
>> in binary object form so it can be relinked with new or
>> modified versions of the LGPL code.
>> In dynamically linked systems, the "relinking" step is
>> automatic and hidden so it is generally considered OK
>> to ship closed source binaries which are dynamically linked.
>> What happens when the library's interface changes and
>> the automatic linking is not an option?  I don't know.
>> Dynamic linking side steps a number of these licensing
>> issues.
> Understood.
> For a statically linked rtems based application am I correct to infer
> the following:
> 1) LGPL code is compatible with the rtems license, provided that one
> complies with the above additional constraint.
> 2) LGPL code, whilst compatible to use with rtems, should not be
> included in the core rtems distributable as it would impose restrictions
> beyond the intention of the rtems license.
Right.  There should never be any code in the core
RTEMS distribution which imposes licensing requirements
on the end user application.  That is why we use GPL+exception,
BSD, public domain, etc for all code that runs on the target.

There are other GPL and LGPL libraries that run on RTEMS
but they are not included in the main RTEMS tarball and
it is purely up to the user to include them.

I never want to find the RTEMS Project in a position where
we have made it easy for a user to accidentally violate a
software license. 
> Keith

Joel Sherrill, Ph.D.             Director of Research & Development
joel.sherrill at OARcorp.com        On-Line Applications Research
Ask me about RTEMS: a free RTOS  Huntsville AL 35805
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