at least a couple of these are used on BSD too, and the FNM_*
namespace is reserved in fnmatch.h anyway.

this is still experimental and subject to change. for git checkouts,
an attempt is made to record the exact revision to aid in bug reports
and debugging. no version information is recorded in the static libc.a
or binaries it's linked into.

the FNM_PATHNAME logic for advancing by /-delimited components was
incorrect when the / character was escaped (i.e. \/), and a final \ at
the end of pattern was not handled correctly.

a '/' in the pattern could be incorrectly matched against the
terminating null byte in the string causing arbitrarily long
sequence of out-of-bounds access in fnmatch("/","",FNM_PATHNAME)

a v6 socket will only be used if there is at least one v6 nameserver
address. if the kernel lacks v6 support, the code will fall back to
using a v4 socket and requests to v6 servers will silently fail. when
using a v6 socket, v4 addresses are converted to v4-mapped form and
setsockopt is used to ensure that the v6 socket can accept both v4 and
v6 traffic (this is on-by-default on Linux but the default is
configurable in /proc and so it needs to be set explicitly on the
socket level). this scheme avoids increasing resource usage during
lookups and allows the existing network io loop to be used without
modification.

previously, nameservers whose address family did not match the address
family of the first-listed nameserver were simply ignored. prior to
recent __ipparse fixes, they were not ignored but erroneously parsed.

the old value of 20 was reported by Laurent Bercot as being
insufficient for a reasonable real-world usage case. actual problem
was the internal buffer used by ttyname(), but the implementation of
ttyname uses TTY_NAME_MAX, and for consistency it's best to increase
both. the new value is aligned with glibc.

subsequent code assumes the address family requested is either
unspecified or one of IPv4/IPv6, and could malfunction if this
constraint is not met, so other address families should be explicitly
rejected.

on archs with excess precision, the floating point constant 1e40f may
be evaluated such that it does not actually produce an infinity.
1e5000f is sufficiently large to produce an infinity for all supported
floating point formats. note that this definition of INFINITY is only
used for old or non-GNUC compilers anyway; despite being a portable,
conforming definition, it leads to erroneous warnings on many
compilers and thus using the builtin is preferred.

these functions were spuriously failing in the case where the buffer
size was exactly the number of bytes/characters to be written,
including null termination. since these functions do not have defined
error conditions other than buffer size, a reasonable application may
fail to check the return value when the format string and buffer size
are known to be valid; such an application could then attempt to use a
non-terminated buffer.

in addition to fixing the bug, I have changed the error handling
behavior so that these functions always null-terminate the output
except in the case where the buffer size is zero, and so that they
always write as many characters as possible before failing, rather
than dropping whole fields that do not fit. this actually simplifies
the logic somewhat anyway.

unfortunately this eliminates the ability of the compiler to diagnose
some dangerous/incorrect usage, but POSIX requires (as an extension to
the C language, i.e. CX shaded) that NULL have type void *. plain C
allows it to be defined as any null pointer constant.

the definition 0L is preserved for C++ rather than reverting to plain
0 to avoid dangerous behavior in non-conforming programs which use
NULL as a variadic sentinel. (it's impossible to use (void *)0 for C++
since C++ lacks the proper implicit pointer conversions, and other
popular alternatives like the GCC __null extension seem non-conforming
to the standard's requirements.)

This function is used by ping6 from iputils.

- remove the HAVE_EFFICIENT_IRINT case: fn is an exact integer, so
  it can be converted to int32_t a bit more efficiently than with a
  cast (the rounding mode change can be avoided), but musl does not
  support this case on any arch.
- __rem_pio2: use double_t where possible
- __rem_pio2f: use less assignments to avoid stores on i386
- use unsigned int bit manipulation (and union instead of macros)
- use hexfloat literals instead of named constants

some macros in sys/mtio.h and syslog.h used NULL without defining it

definition in linux:
 #define O_TMPFILE (__O_TMPFILE | O_DIRECTORY)
where __O_TMPFILE and O_DIRECTORY are arch specific

and use _GNU_SOURCE || _BSD_SOURCE guards for all of the RFC 3678
namespace polluting things like glibc/uclibc does.

This way, if an fprintf fails, we get an incomplete group entry rather
than a corrupted one.

If *l == *r && *l, then by transitivity, *r.

previously:
timersub(&now, t, &diff);

warning: value computed is not used [-Wunused-value]

loop condition was incorrect and confusing and caused an infinite loop
when (broken) applications reaped the pid from a signal handler or
another thread before wordexp's call to waitpid could do so.

when WRDE_NOSPACE is returned, the we_wordv and we_wordc members must
be valid, because the interface contract allows them to return partial
results.

in the case of zero results (due either to resource exhaustion or a
zero-word input) the we_wordv array still should contain a terminating
null pointer and the initial we_offs null pointers. this is impossible
on resource exhaustion, so a correct application must presumably check
for a null pointer in we_wordv; POSIX however seems to ignore the
issue. the previous code may have crashed under this situation.

avoid using exit status to determine if a shell error occurred, since
broken programs may install SIGCHLD handlers which reap all zombies,
including ones that don't belong to them. using clone and __WCLONE
does not seem to work for avoiding this problem since exec resets the
exit signal to SIGCHLD.

instead, the new code uses a dummy word at the beginning of the
shell's output, which is ignored, to determine whether the command was
executed successfully. this also fixes a corner case where a word
string containing zero words was interpreted as a single zero-length
word rather than no words at all. POSIX does not seem to require this
case to be supported anyway, though.

in addition, the new code uses the correct retry idiom for waitpid to
ensure that spurious STOP/CONT signals in the child and/or EINTR in
the parent do not prevent successful wait for the child, and blocks
signals in the child.

* simplify sin_pi(x) (don't care about inexact here, the result is
  inexact anyway, and x is not so small to underflow)
* in lgammal add the previously removed special case for x==1 and
  x==2 (to fix the sign of zero in downward rounding mode)
* only define lgammal on supported long double platforms
* change tgamma so the generated code is a bit smaller

previously these macros wrongly had type double rather than long
double. I see no way an application could detect the error in C99, but
C11's _Generic can trivially detect it.

at the same time, even though these archs do not have excess
precision, the number of decimal places used to represent these
constants has been increased to 21 to be consistent with the decimal
representations used for the DBL_* macros.

this is enough to produce the correct value even if the constant is
interpreted as 80-bit extended precision, which matters on archs with
excess precision (FLT_EVAL_METHOD==2) under at least some
interpretations of the C standard. the shorter representations, while
correct if converted to the nominal precision at translation time,
could produce an incorrect value at extended precision, yielding
results such as (double)DBL_MAX != DBL_MAX.

this should not matter since the reality is that either all the sysv
sem syscalls are individual syscalls, or all of them are multiplexed
on the SYS_ipc syscall (depending on arch). but best to be consistent
anyway.