Re: closedir()

[Rich Felker <dalias@libc.org>]

On Thu, Jan 31, 2019 at 09:58:06PM +0000, De Paula, Judah wrote:
> Hi MUSLers,
> 
> Possible bug report? I’m not on your DL, but would like to hear back
> if you find this helpful.
> 
> I’m working on an internal corporate application using Docker and
> Alpine. Under normal Fedora my app calls closedir(NULL) and a -1 is
> returned. Under MUSL, it segfaults. I’m changing the code to not
> call closedir() with a null pointer, but I’m not certain segfaults
> are considered Working As Designed.
> 
> http://man7.org/linux/man-pages/man3/closedir.3.html

Hi,

Passing an invalid pointer to closedir is undefined behavior, and in
musl the preferred effect for undefined behavior when it's not costly
to attempt to detect is a quick crash so that the point of error in
the program can be identified and fixed.

For what it's worth, glibc has also adopted this view based on text I
wrote:

https://sourceware.org/glibc/wiki/Style_and_Conventions#Invalid_pointers

However I doubt they will change existing functions where they have
traditionally accepted null arguments as a nop.

Rich