Increased RAM usage after upgrade to newlib 4.3.0

[Sebastian Huber]

Hello Patrick,

On 17.02.23 20:10, Patrick Bader wrote:
> Dear newlib group members,
> 
> I have just updated my firmware from newlib 4.2.0 to newlib 4.3.0 from 
> the Arch Linux packages and found out that static memory consumption 
> rose by about 300 bytes due to the standard input and output streams.
> However, I am not using these streams, but am using dynamic memory, 
> which is using the _reent struct internally.
> 
> As I found out, this struct is always populated with the global __sf 
> file descriptors in the 4.3.0 version of newlib, which are about 300 
> bytes in total.
> The library is built with --enable-newlib-reent-small with the nano.spec 
> and in the 4.2.0 version, _reent is initialized with some fake file 
> descriptors: "__sf_fake_stdin,..." which are way smaller.
> Those fake versions are missing in newlib 4.3.0 and the __sf descriptors 
> are used always.
> 
> Is this intended behaviour or a regression? If it is intended, is there 
> a way or some flag to get rid of the extra 300 bytes?
> I also do not need all those functions to be reentrant, but found no 
> compilation parameter to turn this off.

this regression is probably a side-effect of the support for splitting 
up the struct _reent into individual thread-local storage objects. See 
the --enable-newlib-reent-thread-local configuration option.

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