Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

clang 20 issues an warning for the unused '-c' argument used to create
errlist-data-aux-shared.S, errlist-data-aux.S, siglist-aux-shared.S,
and siglist-aux.S.  Filter out the '-c' from the $(compile-command.c).

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

The clang default to warning for missing fall-through and it does
not support all comment-like annotation that gcc does.  Use C23
[[fallthrough]] annotation instead.
proper attribute instead.

Reviewed-by: Collin Funk <collin.funk1@gmail.com>

clang emits an error while building vfprintf-internal for default
case:

error: result of comparison of constant 255 with expression of type
'char' is always true
[-Werror,-Wtautological-constant-out-of-range-compare]
          if (spec <= UCHAR_MAX

The test is indeed not required for default non-wide build.

Reviewed-by: Collin Funk <collin.funk1@gmail.com>

The warning is not supported by clang.

Reviewed-by: Sam James <sam@gentoo.org>

A late change in C23, the resolution to CD2 comment GB-108, specified
that <inttypes.h> macros such as PRId8 expand to formats such that,
when an argument is passed in the promoted type that isn't
representable in the original type such as int8_t corresponding to the
format, it gets converted to that type before printing.  (Previously,
the proper handling of such arguments was unclear; the case of direct
use of formats such as %hhd was clarified earlier in C23 development,
and had been fixed in glibc in 2006.)  Implement the change to use
formats such as "hhd" for the affected macros, with associated tests.

Tested for x86_64 and x86.

Linux uses different expressions for the RENAME_* and AT_RENAME_*
constants.  Mirror that in <stdio.h>, so that the macro redefinitions
do not result in preprocessor warnings.

Reviewed-by: Collin Funk <collin.funk1@gmail.com>

Convert (some) tests to use 'xfclose' rather than using plain 'fclose'
call with no error checking or plain missing such a call.

Reviewed-by: Florian Weimer <fweimer@redhat.com>

Convert tests to use 'xfmemopen' rather than open-coding error checks
with 'fmemopen' or plain missing them, where 'fmemopen' itself is not
the scope of testing.  Leave 'fmemopen' tests alone.

Reviewed-by: Florian Weimer <fweimer@redhat.com>