Re: [musl] Bug: ftell() after fopen(..., "ab") returns 0 unless an explicit fseek() is used first

[Florian Weimer <fweimer@redhat.com>]

* Robert Buchholz:

> On my Alpine/MUSL setup this prints "0 6" while on Ubuntu 22.04 with
> glibc it prints "3 6" - which I'm assuming is the expected output.

Both behaviors are acceptable.  C11 (7.21.3p1) says this:

| If a file can support positioning requests (such as a disk file, as
| opposed to a terminal), then a file position indicator associated with
| the stream is positioned at the start (character number zero) of the
| file, unless the file is opened with append mode in which case it is
| implementation-defined whether the file position indicator is initially
| positioned at the beginning or the end of the file.

musl is likely not the only libc with this type of behavior, given that
it's explicitly allowed by the standard.

Thanks,
Florian