[Bug libc/30958] mkstemp always produces the same temp file if it's removed

["adhemerval.zanella at linaro dot org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=30958

--- Comment #4 from Adhemerval Zanella <adhemerval.zanella at linaro dot org> ---
(In reply to Sterpu Mihai from comment #2)
> Questions (as a newbie in this universe):
> Are glibc and gnulib completely independent of each other?
> If yes, then can I propose a patch so the implementation uses the ASLR also
> in gnulib, like it does on glibc?
> If no and they have some sort of sync, why isn't the code synced already?

The glibc is not used in the MinGW environment, it supports only Linux and GNU
Hurd.  The tempname.c is *shared* between gnulib and glibc; but occasionally
they are kept out of sync.  The gnulib is also used on multiple projects to
provide a layer that fixes broken POSIX interfaces and adds GNU extensions.

The latest gnulib changed the way to get the initial entropy to avoid bleeding
ASLR information.  It now always issues getrandom and iff it fails for some
reason it will use the clock and a simple polynomial to get some entropy.

Also, getentropy is implemented differently depending on the system (gnulib
lib/getrandom.c).  On glibc is just a wrapper over Linux getrandom syscall,
while on Linux it tries to use either BCryptGenRandom/CryptGenRandom.

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