Re: [PATCH] libstdc++: testsuite: fs rename to self may fail

[Alexandre Oliva <oliva@adacore.com>]

On Jun 22, 2022, Jonathan Wakely <jwakely@redhat.com> wrote:

> On Wed, 22 Jun 2022 at 08:02, Alexandre Oliva via Libstdc++
> <libstdc++@gcc.gnu.org> wrote:
>> 
>> Hello, Sebastian,
>> 
>> On Jun 22, 2022, Sebastian Huber <sebastian.huber@embedded-brains.de> wrote:
>> 
>> > On 22/06/2022 08:24, Alexandre Oliva via Libstdc++ wrote:
>> >> rtems6's rename() implementation errors with EEXIST when the rename-to
>> >> filename exists, even when renaming a file to itself or when renaming
>> >> a nonexisting file.  Adjust expectations.
>> >>
>> >> Regstrapped on x86_64-linux-gnu, also tested with a cross to
>> >> aarch64-rtems6.  Ok to install?
>> >>
>> >> PS:https://devel.rtems.org/ticket/2169  doesn't seem to suggest plans to
>> >> change behavior so as to comply with POSIX.
>> 
>> > I would not adjust the test case to cope with systems which are not in
>> > line with POSIX.
>> 
>> My understanding is that the libstdc++ testsuite is not meant to test
>> for POSIX conformance, but for conformance with the C++ language
>> standards.
>> 
>> C++ inherits rename from C, and C says the behavior is implementation
>> defined if the new name already exists.

> std::filesystem::rename is explicitly specified in terms of POSIX
> rename, not C rename.

Oh, sorry, I stand corrected.  I meant ::rename only.  My mind seems to
still resist the notion that <filesystem> is standard C++, rather than
an experimental extension proposal :-)

Anyway, I did not realize it deferred to POSIX semantics, even when
that's stricter than C standard.  Interesting...

> Instead, the implementation of std::filesystem::rename should have a
> special-case for rtems (and maybe other targets) that implements the
> POSIX rename semantics if calling ::rename isn't good enough.

Given what I've just learned, I agree.  Patch withdrawn.  I suppose the
other patch, on subdir renaming, must share the same fate.

/me longs for XFAILs for libstdc++ subtests ;-)

-- 
Alexandre Oliva, happy hacker                https://FSFLA.org/blogs/lxo/
   Free Software Activist                       GNU Toolchain Engineer
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