[PATCH] free: preserve errno [BZ#17924]

[Carlos O'Donell]

On 12/20/20 3:25 PM, Paul Eggert wrote:
> * malloc/Makefile (tests): Add tst-free-errno.
> * malloc/malloc.c (tcache_init): Preserve errno when initializing,
> since 'free' might be calling us.
> (__libc_free): Preserve errno when calling munmap.
> * malloc/tst-free-errno.c: New file, almost all from Bruno Haible.
> * manual/memory.texi (Freeing after Malloc, Replacing malloc):
> Document that free preserves errno.

Please provide a reasonable commit message.

-- 
Cheers,
Carlos.