Re: [musl] Question about the exit()

[Rich Felker <dalias@libc.org>]

On Fri, Aug 30, 2024 at 01:34:58PM +0000, JinCheng Li wrote:
> Hi
> 
> I have one question in exit().
> Why is the __libc_exit_fini executed after __funcs_on_exit? If some

Because that is the contract.

> finalized functions in .fini_array access global variables which is
> registered by __cxa_atexit and will be release in __funcs_on_exit,
> we may run into some crash during __libc_exit_fini executaion.

Then that's a bug in the atexit handler. It should not be freeing
anything that could later be needed by a destructor or by any thread
that may still be running concurrent with exit. In general, freeing
anything from an atexit handler is a bug. See Rust issue 126600 where
this is discussed in detail:

https://github.com/rust-lang/rust/issues/126600

> In bionic, I found the fini_array functions may be registered at the
> last before we execute main function and called firstly in
> exit(before global variables release) . Its order looks like
> completely opposite to musl.

I don't follow. What do you mean by "registered last"? After what? And
where is this "global variables release" coming from?

Rich