impure_data never reclaimed (unless you add the required cleanup code)

[Dave Nadler]

Hi Fabian - Yes, that is correct, you need that cleanup code.
However, you must also allocate (and clean up) the reentrancy structure 
for each task/thread.
FreeRTOS correctly does this on task/thread creation and cleanup (with 
#define configUSE_NEWLIB_REENTRANT  1).
Hope that helps!
Best Regards, ,Dave

On 12/5/2020 9:27 AM, Fabian Vogt wrote:
> Hi,
>
> I'm using newlib as libc on top of an OS which provides malloc and free.
> Threads aren't supported, but programs can be started and stopped. The used
> heap is shared between all programs, so leaked memory is lost forever. Thus
> it is important that after a clean exit, every allocation was properly freed.
>
> Currently this simple program leaks three allocations though:
>
> #include <stdio.h>
> int main()
> {
>      setbuf(stdout, NULL); // This would be properly freed, avoid distraction
>      printf("This is 0.5 as a float: %f\n", 0.5f);
> }
>
> Those are from Balloc, which allocates a list also for later use.
> FWICT, _reclaim_reent takes care of freeing the list and its contents, but:
> - _reclaim_reent is never called for _impure_ptr (== &impure_data)
> - _reclaim_reent does nothing if impure_ptr is passed
>
> Is the OS glue code supposed to do something like this in _exit?
>
>      struct _reent *global_reent = _impure_ptr;
>      _impure_ptr = NULL;
>      _reclaim_reent(global_reent);
>
> With that the leaks are gone, but it seems a bit odd to me.
>
> Thanks,
> Fabian


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Dave Nadler, USA East Coast voice (978) 263-0097, drn@nadler.com, Skype
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