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>

Use __thread variables directly instead.  The macros do not save any
typing.  It seems unlikely that a future port will lack __thread
variable support.

Some of the __libc_tsd_* variables are referenced from assembler
files, so keep their names.  Previously, <libc-tls.h> included
<tls.h>, which in turn included <errno.h>, so a few direct includes
of <errno.h> are now required.

Reviewed-by: Frédéric Bérat <fberat@redhat.com>

Use empty initializer to silence GCC 4.9 or older:

getaddrinfo.c: In function ‘gaih_inet’:
getaddrinfo.c:1135:24: error: missing braces around initializer [-Werror=missing-braces]
       / sizeof (struct gaih_typeproto)] = {0};
                        ^

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Sam James <sam@gentoo.org>

This reverts commit 8aa2a9e0339215012354f3c4a262edda838134e8.

as not all targets need braces.

Use "main (void)" instead of "main (void)" to avoid GCC 4.9 warning:

tst-difftime.c:62:1: error: function declaration isn’t a prototype [-Werror=strict-prototypes]
 main ()
 ^
tst-difftime.c: In function ‘main’:
tst-difftime.c:62:1: error: old-style function definition [-Werror=old-style-definition]
cc1: all warnings being treated as errors

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

Since GCC 4.9 doesn't have __builtin_add_overflow:

In file included from tst-stringtable.c:180:0:
stringtable.c: In function ‘stringtable_finalize’:
stringtable.c:185:7: error: implicit declaration of function ‘__builtin_add_overflow’ [-Werror=implicit-function-declaration]
       else if (__builtin_add_overflow (previous->offset,
       ^

return EXIT_UNSUPPORTED for GCC 4.9 or older.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Sam James <sam@gentoo.org>

Add braces to silence GCC 4.9 or older:

getaddrinfo.c: In function ‘gaih_inet’:
getaddrinfo.c:1135:24: error: missing braces around initializer [-Werror=missing-braces]
       / sizeof (struct gaih_typeproto)] = {0};
                        ^

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Sam James <sam@gentoo.org>

This is needed to avoid link failures for the timer_* functions on
Hurd.

Tested with build-many-glibcs.py for i686-gnu.