[RSB 1/3] 6/7: Update Newlib

Chris Johns chrisj at rtems.org
Wed Jul 20 20:52:33 UTC 2022

On 20/7/2022 6:20 pm, Sebastian Huber wrote:
> On 20/07/2022 10:11, Chris Johns wrote:
>>>> Are these TLS allocations in newlib based on a single use of a newlib call that
>>>> brings in the reent stuff? How does that work?
>>> No, each TLS object is defined in the translation unit which uses the object.
>>> The goal is to get only those objects linked in which are needed. Currently, the
>>> Newlib thread delete hook pulls in some objects, however, this dependency will
>>> go away once the TLS destructors are implemented.
>> If I have task A and it opens a file and writes something to a file system will
>> it pull in the TLS support for files?
> Yes.
>> Given the TLS support is static does this mean all threads in the A app allocate
>> the newlib file TLS variables even if they never use newlib?
> Yes.
>> My understanding of the existing reent support is tasks that do not use newlib
>> it never allocate a reent struct?
> No, the struct _reent is allocated for all tasks if you don't use
> CONFIGURE_DISABLE_NEWLIB_REENTRANCY (which is not recommended). How would you
> know if a task doesn't use Newlib?

I thought the get would do a check and then allocate on first use. It has been
many years since I looked at the implementation.

I think this change is a good one because it will reduce the needed memory to
the amount used and it will have better performance.

I think option you post is a good thing to add, maybe as
--enable-newlib-reent-tls. What will be the default?


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