fopen from within a pthread

[Paul Pluzhnikov via libc-help]

On Sat, Jun 2, 2018 at 3:31 PM Martin Beynon <mebeyn@gmail.com> wrote:
>
> Is this erroneous behaviour, or can this be explained in some way?


There is nothing erroneous about it.

What you are observing is the creation of thread-specific arena, from
which malloc will return memory to the new thread.

GLIBC uses thread-specific arenas to avoid having to lock malloc
internal structures when multiple threads allocate and free memory.
Additional info can be found here:
https://sourceware.org/glibc/wiki/MallocInternals



-- 
Paul Pluzhnikov