lib: remove CONSTCOND comment

Since 2021-01-31, lint doesn't need it anymore for the common pattern of
'do ... while (0)'.

make more descriptors that we open as close-on-exec

PR/45989: Martin Husemann: lint invocation does include -w only on i386

- turn lint -w for all the platforms after fixing the lint warnings.
- add _DIAGASSERTS() for casts that would assign values to types that
would not fit.
- change types, add casts
- change into ansii prototypes
- turn on _DIAGNOSTIC for libc (during current, to be eliminated for release
builds)

approved by core@

branches: 1.36.4;
Introduce __weakref_visible to handle the different required visibility
for weak references. GCC 4.2+ and Clang require static, older GCC wants
extern. Change __weak_reference to include sym. This requires changes
the existing users to not reuse the name of the symbol, but avoids
further differences between GCC 4.1 and GCC 4.2+/clang.

Support the different weakref semantic in GCC 4.2 and clang.

branches: 1.34.4;
sign-compare fix

branches: 1.33.6;
Changee __attribute(__weak__) to __weak_reference(). Produces same object code
and matches lib/csu/common_elf/common.h. Fixes linkage with PCC.

branches: 1.32.2;
Remove clause 3 and 4 from TNF licenses

branches: 1.31.16;
fix incomplete initializers

WARNS=4

_nsdispatching needs to count, not just be 1 or 0. Also shuffle around
its use a little to eliminate some duplication.

branches: 1.28.2;
* Improve the comments in <nsswitch.h>
* Provide some more useful default ns_src arrays.

* Re-number NS_FORCEALL from 1<<7 to 1<<8, moving it out of the "public"
bitrange for nsdispatch(3) return values.
* Tweak documentation comments in nsswitch.h
* Ensure the result from the back-end method is masked with
NS_STATUSMASK before nsdispatch(3) returns it.

Implement NS_FORCEALL, which may be set in defaults[0].flags by a caller of
nsdispatch(3) to indicate that all available database methods for a source
will be invoked. This is useful for functions such as endgrent(3).

also ensure defaults != NULL

Fix non-ELF case in _nsloadmod().

Prevent a deadlock that could occur if we try to update the configuration
data structures during a recursive call to nsdispatch() by keeping a record
of which threads are inside nsdispatch() at any given time.

Add support for dynamically loading nsswitch modules on ELF platforms.
Adapted from FreeBSD. Maintains full backward API / ABI compatbility
with built-in-only nsdispatch().

While here, also make nsdispatch() itself thread-safe.

Use ANSI function decls.

remove stray NSUNLOCK(); pointed out by Brian Ginsbach.

make this thread-safe.

__STDC__ is always defined on NetBSD.

branches: 1.17.2;
remove redundant declarations.

Delint.
Remove trailing ; from uses of __weak_alias(). The macro inserts this if
needed.

don't use err(); instead pass an error condition back to a higher
layer to warn() about.

branches: 1.14.4;
back out the #ifdef _DIAGNOSTIC argument checks; too many people complained.
_DIAGASSERT() is still retained.

return NS_UNAVAIL if args are dodgy

* use _DIAGASSERT() to check pointer arguments against NULL and file
descriptors against -1 (as appropriate).
* add actual checks which to detect stuff that would trigger_DIAGASSERT(),
and attempt to return a sane error condition.
* knf some code
* remove some `register' decls.

the first two items result in the addition of code similar to the
following in various functions:

_DIAGASSERT(path != NULL)
#ifdef _DIAGNOSTIC
if (path == NULL) {
errno = EFAULT;
return (-1);
}
#endif

sprinkle argsused till lint smiles at you.

specifically include stdarg/varargs.h

add rcsids

minor knf; don't exceed 80 columns ;)

- add ARGSUSED
- remove unnecessary casts
- const poisoning

weak_alias nsdispatch

* support extra two arguments to nsdispatch():
const char *method /* method name for dynamic linking */
const ns_src defaults[] /* list of defaults */
* document above, and expand other docco.

fix thinko introduced in last rototilling of nsdispatch; _nsdbtget()
would always return the entry for the first entry looked up. noted by
andrew gillham (manifesting itself as ftp failing to lookup names).

remove debugging override of _PATH_NS_CONF

merge nsswitch into main branch

branches: 1.1.2; 1.1.4;
file nsdispatch.c was initially added on branch nsswitch.