This adds a special SHM_ANON value that can be passed into shm_open ()
in place of a name. When called in this way, shm_open () will create a
new anonymous shared memory file. The file will be created in the same
way that other shared memory files are created (i.e., under /dev/shm/),
except that it is not given a name and therefore cannot be reached from
the file system, nor by other calls to shm_open (). This is accomplished
by utilizing O_TMPFILE.
This is intended to be compatible with FreeBSD's API of the same name.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230130125216.6254-4-bugaevc@gmail.com>
This is a flag that causes open () to create a new, unnamed file in the
same filesystem as the given directory. The file descriptor can be
simply used in the creating process as a temporary file, or shared with
children processes via fork (), or sent over a Unix socket. The file can
be left anonymous, in which case it will be deleted from the backing
file system once all copies of the file descriptor are closed, or given
a permanent name with a linkat () call, such as the following:
int fd = open ("/tmp", O_TMPFILE | O_RDWR, 0700);
/* Do something with the file... */
linkat (fd, "", AT_FDCWD, "/tmp/filename", AT_EMPTY_PATH);
In between creating the file and linking it to the file system, it is
possible to set the file content, mode, ownership, author, and other
attributes, so that the file visibly appears in the file system (perhaps
replacing another file) atomically, with all of its attributes already
set up.
The Hurd support for O_TMPFILE directly exposes the dir_mkfile RPC to
user programs. Previously, dir_mkfile was used by glibc internally, in
particular for implementing tmpfile (), but not exposed to user programs
through a Unix-level API.
O_TMPFILE was initially introduced by Linux. This implementation is
intended to be compatible with the Linux implementation, except that the
O_EXCL flag is not given the special meaning when used together with
O_TMPFILE, unlike on Linux.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20230130125216.6254-3-bugaevc@gmail.com>
This addition to the list of source headers in
sysdeps/mach/hurd/bits/errno.h appears in the source tree after
build-many-glibcs.py runs, I'm guessing resulting from gnumach commit
c566ad85a2d6728ebc8ec0f461a3b35df300e96e.
The inline and library functions that the CMSG_NXTHDR macro may expand
to increment the pointer to the header before checking the stride of
the increment against available space. Since C only allows incrementing
pointers to one past the end of an array, the increment must be done
after a length check. This commit fixes that and includes a regression
test for CMSG_FIRSTHDR and CMSG_NXTHDR.
The Linux, Hurd, and generic headers are all changed.
Tested on Linux on armv7hl, i686, x86_64, aarch64, ppc64le, and s390x.
[BZ #28846]
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
It was added on Linux 5.4 (3695eae5fee0605f316fbaad0b9e3de791d7dfaf)
to extend waitid to wait on pidfd.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
I used these shell commands:
../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")
and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 7061 files FOO.
I then removed trailing white space from math/tgmath.h,
support/tst-support-open-dev-null-range.c, and
sysdeps/x86_64/multiarch/strlen-vec.S, to work around the following
obscure pre-commit check failure diagnostics from Savannah. I don't
know why I run into these diagnostics whereas others evidently do not.
remote: *** 912-#endif
remote: *** 913:
remote: *** 914-
remote: *** error: lines with trailing whitespace found
...
remote: *** error: sysdeps/unix/sysv/linux/statx_cp.c: trailing lines
Now that Hurd implementis both close_range and closefrom (f2c996597d),
we can make close_range() a base ABI, and make the default closefrom()
implementation on top of close_range().
The generic closefrom() implementation based on __getdtablesize() is
moved to generic close_range(). On Linux it will be overriden by
the auto-generation syscall while on Hurd it will be a system specific
implementation.
The closefrom() now calls close_range() and __closefrom_fallback().
Since on Hurd close_range() does not fail, __closefrom_fallback() is an
empty static inline function set by__ASSUME_CLOSE_RANGE.
The __ASSUME_CLOSE_RANGE also allows optimize Linux
__closefrom_fallback() implementation when --enable-kernel=5.9 or
higher is used.
Finally the Linux specific tst-close_range.c is moved to io and
enabled as default. The Linuxism and CLOSE_RANGE_UNSHARE are
guarded so it can be built for Hurd (I have not actually test it).
Checked on x86_64-linux-gnu, i686-linux-gnu, and with a i686-gnu
build.
The close_range () function implements the same API as the Linux and
FreeBSD syscalls. It operates atomically and reliably. The specified
upper bound is clamped to the actual size of the file descriptor table;
it is expected that the most common use case is with last = UINT_MAX.
Like in the Linux syscall, it is also possible to pass the
CLOSE_RANGE_CLOEXEC flag to mark the file descriptors in the range
cloexec instead of acually closing them.
Also, add a Hurd version of the closefrom () function. Since unlike on
Linux, close_range () cannot fail due to being unuspported by the
running kernel, a fallback implementation is never necessary.
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
Message-Id: <20211106153524.82700-1-bugaevc@gmail.com>
I used these shell commands:
../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")
and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 6694 files FOO.
I then removed trailing white space from benchtests/bench-pthread-locks.c
and iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c, to work around this
diagnostic from Savannah:
remote: *** pre-commit check failed ...
remote: *** error: lines with trailing whitespace found
remote: error: hook declined to update refs/heads/master
It refactor how signals are defined by each architecture. Instead of
include a generic header (bits/signum-generic.h) and undef non-default
values in an arch specific header (bits/signum.h) the new scheme uses a
common definition (bits/signum-generic.h) and each architectures add
its specific definitions on a new header (bits/signum-arch.h).
For Linux it requires copy some system default definitions to alpha,
hppa, and sparc. They are historical values and newer ports uses
the generic Linux signum-arch.h.
For Hurd the BSD signum is removed and moved to a new header (it is
used currently only on Hurd).
Checked on a build against all affected ABIs.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
The __suseconds64_t type is supposed to be the 64 bit type across all
architectures.
It would be mostly used internally in the glibc - however, when passed to
Linux kernel (very unlikely), if necessary, it shall be converted to 32
bit type (i.e. __suseconds_t)
Build tests:
./src/scripts/build-many-glibcs.py glibcs
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Add a new macro __STATFS_MATCHES_STATFS64 that specifies if fsblkcnt_t
matches fsblkcnt64_t and if fsfilcnt_t matches fsfilcnt64_t.
As we don't have the padding we also need to update the overflow checker
to not access the undefined members.
This patch fixes the OFD ("file private") locks for architectures that
support non-LFS flock definition (__USE_FILE_OFFSET64 not defined). The
issue in this case is both F_OFD_{GETLK,SETLK,SETLKW} and
F_{SET,GET}L{W}K64 expects a flock64 argument and when using old
F_OFD_* flags with a non LFS flock argument the kernel might interpret
the underlying data wrongly. Kernel idea originally was to avoid using
such flags in non-LFS syscall, but since GLIBC uses fcntl with LFS
semantic as default it is possible to provide the functionality and
avoid the bogus struct kernel passing by adjusting the struct manually
for the required flags.
The idea follows other LFS interfaces that provide two symbols:
1. A new LFS fcntl64 is added on default ABI with the usual macros to
select it for FILE_OFFSET_BITS=64.
2. The Linux non-LFS fcntl use a stack allocated struct flock64 for
F_OFD_{GETLK,SETLK,SETLKW} copy the results on the user provided
struct.
3. Keep a compat symbol with old broken semantic for architectures
that do not define __OFF_T_MATCHES_OFF64_T.
So for architectures which defines __USE_FILE_OFFSET64, fcntl64 will
aliased to fcntl and no adjustment would be required. So to actually
use F_OFD_* with LFS support the source must be built with LFS support
(_FILE_OFFSET_BITS=64).
Also F_OFD_SETLKW command is handled a cancellation point, as for
F_SETLKW{64}.
Checked on x86_64-linux-gnu and i686-linux-gnu.
[BZ #20251]
* NEWS: Mention fcntl64 addition.
* csu/check_fds.c: Replace __fcntl_nocancel by __fcntl64_nocancel.
* login/utmp_file.c: Likewise.
* sysdeps/posix/fdopendir.c: Likewise.
* sysdeps/posix/opendir.c: Likewise.
* sysdeps/unix/pt-fcntl.c: Likewise.
* include/fcntl.h (__libc_fcntl64, __fcntl64,
__fcntl64_nocancel_adjusted): New prototype.
(__fcntl_nocancel_adjusted): Remove prototype.
* io/Makefile (routines): Add fcntl64.
(CFLAGS-fcntl64.c): New rule.
* io/Versions [GLIBC_2.28] (fcntl64): New symbol.
[GLIBC_PRIVATE] (__libc_fcntl): Rename to __libc_fcntl64.
* io/fcntl.h (fcntl64): Add prototype and redirect if
__USE_FILE_OFFSET64 is defined.
* io/fcntl64.c: New file.
* manual/llio.text: Add a note for which commands fcntl acts a
cancellation point.
* nptl/Makefile (CFLAGS-fcntl64.c): New rule.
* sysdeps/mach/hurd/fcntl.c: Alias fcntl to fcntl64 symbols.
* sysdeps/mach/hurd/i386/libc.abilist [GLIBC_2.28] (fcntl, fcntl64):
New symbols.
* sysdeps/unix/sysv/linux/fcntl.c (__libc_fcntl): Fix F_GETLK64,
F_OFD_GETLK, F_SETLK64, F_SETLKW64, F_OFD_SETLK, and F_OFD_SETLKW for
non-LFS case.
* sysdeps/unix/sysv/linux/fcntl64.c: New file.
* sysdeps/unix/sysv/linux/fcntl_nocancel.c (__fcntl_nocancel): Rename
to __fcntl64_nocancel.
(__fcntl_nocancel_adjusted): Rename to __fcntl64_nocancel_adjusted.
* sysdeps/unix/sysv/linux/not-cancel.h (__fcntl_nocancel): Rename
to __fcntl64_nocancel.
* sysdeps/unix/sysv/linux/tst-ofdlocks.c: New file.
* sysdeps/unix/sysv/linux/tst-ofdlocks-compat.c: Likewise.
* sysdeps/unix/sysv/linux/Makefile (tests): Add tst-ofdlocks.
(tests-internal): Add tst-ofdlocks-compat.
* sysdeps/unix/sysv/linux/aarch64/libc.abilist [GLIBC_2.28]
(fcntl64): New symbol.
* sysdeps/unix/sysv/linux/alpha/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/ia64/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc64/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc64/libc-le.abilist: Likewise.
* sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/x86_64/64/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/arm/libc.abilist [GLIBC_2.28] (fcntl,
fcntl64): Likewise.
* sysdeps/unix/sysv/linux/hppa/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/i386/libc.abilis: Likewise.
* sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/microblaze/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/nios2/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist:
Likewise.
* sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist:
Likewise.
* sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/sh/libc.abilist: Likewise.
* sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist: Likewise.
* sysdeps/mach/hurd/bits/statfs.h (struct statfs): Make f_bsize,
f_namemax, f_frsize, and f_flag fields unsigned long int instead of
unsigned int.
(struct statfs64): Likewise.
Standards require that the f_bsize, f_frsize, f_flag and f_namemax fields be
unsigned long. They used to be only unsigned on hurd, which happens to be
compatible with unsigned long on the only existing, 32bit, port. We can
thus merely fix the type.
* sysdeps/mach/hurd/bits/statvfs.h (struct statvfs): Make f_bsize,
f_namemax, f_frsize, and f_flag fields unsigned long int instead of
unsigned int.
(struct statvfs64): Likewise.
* hurd/Makefile (routines): Add hurdlock.
* hurd/Versions (GLIBC_PRIVATE): Added new entry to export the above
interface.
(HURD_CTHREADS_0.3): Remove __libc_getspecific.
* hurd/hurdpid.c: Include <lowlevellock.h>
(_S_msg_proc_newids): Use lll_wait to synchronize.
* hurd/hurdsig.c: (reauth_proc): Use __mutex_lock and __mutex_unlock.
* hurd/setauth.c: Include <hurdlock.h>, use integer for synchronization.
* mach/Makefile (lock-headers): Remove machine-lock.h.
* mach/lock-intern.h: Include <lowlevellock.h> instead of
<machine-lock.h>.
(__spin_lock_t): New type.
(__SPIN_LOCK_INITIALIZER): New macro.
(__spin_lock, __spin_unlock, __spin_try_lock, __spin_lock_locked,
__mutex_init, __mutex_lock_solid, __mutex_unlock_solid, __mutex_lock,
__mutex_unlock, __mutex_trylock): Use lll to implement locks.
* mach/mutex-init.c: Include <lowlevellock.h> instead of <cthreads.h>.
(__mutex_init): Initialize with lll.
* manual/errno.texi (EOWNERDEAD, ENOTRECOVERABLE): New errno values.
* sysdeps/mach/Makefile: Add libmachuser as dependencies for libs
needing lll.
* sysdeps/mach/hurd/bits/errno.h: Regenerate.
* sysdeps/mach/hurd/cthreads.c (__libc_getspecific): Remove function.
* sysdeps/mach/hurd/bits/libc-lock.h: Remove file.
* sysdeps/mach/hurd/setpgid.c: Include <lowlevellock.h>.
(__setpgid): Use lll for synchronization.
* sysdeps/mach/hurd/setsid.c: Likewise with __setsid.
* sysdeps/mach/bits/libc-lock.h: Include <tls.h> and <lowlevellock.h>
instead of <cthreads.h>.
(_IO_lock_inexpensive): New macro
(__libc_lock_recursive_t, __rtld_lock_recursive_t): New structures.
(__libc_lock_self0): New declaration.
(__libc_lock_owner_self): New macro.
(__libc_key_t): Remove type.
(_LIBC_LOCK_INITIALIZER): New macro.
(__libc_lock_define_initialized, __libc_lock_init, __libc_lock_fini,
__libc_lock_fini_recursive, __rtld_lock_fini_recursive,
__libc_lock_lock, __libc_lock_trylock, __libc_lock_unlock,
__libc_lock_define_initialized_recursive,
__rtld_lock_define_initialized_recursive,
__libc_lock_init_recursive, __libc_lock_trylock_recursive,
__libc_lock_lock_recursive, __libc_lock_unlock_recursive,
__rtld_lock_initialize, __rtld_lock_trylock_recursive,
__rtld_lock_lock_recursive, __rtld_lock_unlock_recursive
__libc_once_define, __libc_mutex_unlock): Reimplement with lll.
(__libc_lock_define_recursive, __rtld_lock_define_recursive,
_LIBC_LOCK_RECURSIVE_INITIALIZER, _RTLD_LOCK_RECURSIVE_INITIALIZER):
New macros.
Include <libc-lockP.h> to reimplement libc_key* with pthread_key*.
* hurd/hurdlock.c: New file.
* hurd/hurdlock.h: New file.
* mach/lowlevellock.h: New file
* sysdeps/mach/hurd/bits/stat.h [__USE_ATFILE] (UTIME_NOW,
UTIME_OMIT): New macros.
* sysdeps/mach/hurd/futimens.c (__futimens): Try to use __file_utimens
before reverting to converting time spec to time value and calling
__file_utimes.
* sysdeps/mach/hurd/utime-helper.c: New file.
* sysdeps/mach/hurd/futimes.c: Include "utime-helper.c".
(__futimes): Try to use utime_ts_from_tval and __file_utimens before
reverting to utime_tvalue_from_tval and __file_utimes.
* sysdeps/mach/hurd/lutimes.c: Include "utime-helper.c".
(__lutimes): Just call hurd_futimens after lookup.
* sysdeps/mach/hurd/utimes.c: Likewise.
so interfaces needing it can get it.
* stdlib/errno.h (error_t): Move definition to...
* bits/types/error_t.h: ... new header.
* stdlib/Makefile (headers): Add bits/types/error_t.h.
* sysdeps/mach/hurd/bits/errno.h (error_t): Move definition to...
* sysdeps/mach/hurd/bits/types/error_t.h: ... new header.
* sysdeps/mach/hurd/errnos.awk (error_t): Likewise.
* hurd/hurd.h: Include <bits/types/error_t.h>
* hurd/hurd/fd.h: Include <bits/types/error_t.h>
* hurd/hurd/id.h: Include <errno.h> and <bits/types/error_t.h>
* hurd/hurd/lookup.h: Include <errno.h> and <bits/types/error_t.h>
* hurd/hurd/resource.h: Include <bits/types/error_t.h>
* hurd/hurd/signal.h: Include <bits/types/error_t.h>
* hurd/hurd/sigpreempt.h: Include <bits/types/error_t.h>
_POSIX_CHOWN_RESTRICTED and _POSIX_NO_TRUNC should be always defined.
* sysdeps/mach/hurd/bits/posix_opt.h (_POSIX_CHOWN_RESTRICTED,
_POSIX_NO_TRUNC): Define to 0.
* sysdeps/mach/hurd/bits/socket.h: Include <bits/wordsize.h> instead
of <limits.h>
(__need_NULL): Do not define.
(__ss_aligntype): Use __WORDSIZE instead of ULONG_MAX to determine
alignment.
[!__USE_MISC] (pseudo_AF_XTP, pseudo_AF_RTIP, pseudo_AF_PIP,
CMGROUP_MAX, cmsgcred): Do not define.
(CMSG_FIRSTHDR, __cmsg_nxthdr): Use (struct cmsghdr *) 0 instead of
NULL.
* bits/socket.h: Likewise.
This is fairly complicated, not because the users of __need_Emath and
__need_error_t have complicated requirements, but because the core
changes had a lot of fallout.
__need_error_t exists for gnulib compatibility in argz.h and argp.h.
error_t itself is a Hurdism, an enum containing all the E-constants,
so you can do 'p (error_t) errno' in gdb and get a symbolic value.
argz.h and argp.h use it for function return values, and they want to
fall back to 'int' when that's not available. There is no reason why
these nonstandard headers cannot just go ahead and include all of
errno.h; so we do that.
__need_Emath is defined only by .S files; what they _really_ need is
for errno.h to avoid declaring anything other than the E-constants
(e.g. 'extern int __errno_location(void);' is a syntax error in
assembly language). This is replaced with a check for __ASSEMBLER__ in
errno.h, plus a carefully documented requirement for bits/errno.h not
to define anything other than macros. That in turn has the
consequence that bits/errno.h must not define errno - fortunately, all
live ports use the same definition of errno, so I've moved it to
errno.h. The Hurd bits/errno.h must also take care not to define
error_t when __ASSEMBLER__ is defined, which involves repeating all of
the definitions twice, but it's a generated file so that's okay.
* stdlib/errno.h: Remove __need_Emath and __need_error_t logic.
Reorganize file. Declare errno here. When __ASSEMBLER__ is
defined, don't declare anything other than the E-constants.
* include/errno.h: Change conditional for exposing internal
declarations to (not _ISOMAC and not __ASSEMBLER__).
* bits/errno.h: Remove logic for __need_Emath. Document
requirements for a port-specific bits/errno.h.
* sysdeps/unix/sysv/linux/bits/errno.h
* sysdeps/unix/sysv/linux/alpha/bits/errno.h
* sysdeps/unix/sysv/linux/hppa/bits/errno.h
* sysdeps/unix/sysv/linux/mips/bits/errno.h
* sysdeps/unix/sysv/linux/sparc/bits/errno.h:
Add multiple-include guard and check against improper inclusion.
Remove __need_Emath logic. Don't declare errno here. Ensure all
constants are defined as simple integer literals. Consistent
formatting.
* sysdeps/mach/hurd/errnos.awk: Likewise. Only define error_t and
enum __error_t_codes if __ASSEMBLER__ is not defined.
* sysdeps/mach/hurd/bits/errno.h: Regenerate.
* argp/argp.h, string/argz.h: Don't define __need_error_t before
including errno.h.
* sysdeps/i386/i686/fpu/multiarch/s_cosf-sse2.S
* sysdeps/i386/i686/fpu/multiarch/s_sincosf-sse2.S
* sysdeps/i386/i686/fpu/multiarch/s_sinf-sse2.S
* sysdeps/x86_64/fpu/s_cosf.S
* sysdeps/x86_64/fpu/s_sincosf.S
* sysdeps/x86_64/fpu/s_sinf.S:
Just include errno.h; don't define __need_Emath or include
bits/errno.h directly.
Some headers did not include all of their prerequisite headers.
* rpcsvc/nislib.h: Include rpcsvc/nis.h.
* sysdeps/unix/sysv/linux/netrose/rose.h:
Include sys/socket.h and netax25/ax25.h.
<endian.h> only defines BYTE_ORDER, BIG_ENDIAN, LITTLE_ENDIAN,
etc. under __USE_MISC; glibc's headers should use __BYTE_ORDER,
__BIG_ENDIAN, __LITTLE_ENDIAN, etc. instead.
* inet/netinet/icmp6.h, inet/netinet/ip6.h
* resolv/arpa/nameser_compat.h:
Use __BYTE_ORDER etc. instead of BYTE_ORDER etc.
sys/types.h only conditionally defines caddr_t and clockid_t.
* sysdeps/unix/sysv/linux/sys/quota.h:
Use __caddr_t instead of caddr_t.
* sysdeps/unix/sysv/linux/sys/timerfd.h:
Use __clockid_t instead of clockid_t.
Remove a #warning that was the sole actual problem with using sys/ipc.h
without _GNU_SOURCE/_XOPEN_SOURCE.
* sysvipc/sys/ipc.h: Remove unnecessary #warning.
_LIBC, __USE_XOPEN2K8, and __STDC_VERSION__ are not always defined.
It seems to me that _LIBC should not appear in installed headers, but
avoiding that for argp specifically would require more surgery than
feels appropriate for this patch set. It's possible that
"#ifdef _LIBC" would be sufficient, but I wanted to be conservative.
All three versions of bits/socket.h want to know whether __flexarr
will produce a real flexible array member -- specifically, one that
doesn't alter sizeof(the structure containing it). They were testing
for this with a complicated #if condition that did not agree with
sys/cdefs.h and that tripped -Wundef warnings under -std=c90.
I added a new macro to sys/cdefs.h, __glibc_c99_flexarr_available,
which reveals exactly what these headers want to know. I also took
the opportunity to flatten the rather messy conditional nest defining
__flexarr.
* argp/argp.h: Check whether _LIBC is defined before expanding it.
* posix/glob.h: Check whether __USE_XOPEN2K8 is defined instead
of expanding it.
* misc/sys/cdefs.h: Tidy up conditional nest defining __flexarr.
Define __glibc_c99_flexarr_available to 1 when the compiler
supports C99-compatible flexible array members, 0 otherwise.
* sysdeps/unix/sysv/linux/bits/socket.h
* sysdeps/mach/hurd/bits/socket.h
* bits/socket.h: Use __glibc_c99_flexarr_available in
definitions of struct cmsghdr and CMSG_DATA.
