Implement __cxa_thread_atexit and __cxa_thread_atexit_impl. This
functions are used for destructors of thread_local objects.

If a pending destructor exists, prevent unloading of shared objects.
Introduce __dl_cxa_refcount interface for this purpose. When the last
reference is gone and the object has been dlclose'd before, the
unloading is finalized.

Ideally, __cxa_thread_atexit_impl wouldn't exist, but libstdc++ insists
on providing __cxa_thread_atexit as direct wrapper without further
patching.

Add _dlauxinfo helper function to provide access to the ELF auxilary
vector. This can normally be found via __ps_strings, but libc is
initialised too early when linked dynamically and doesn't have access to
it yet, so provide an alternative mechanism via ld.elf_so.
Bump libc minor.

branches: 1.23.2;
PR/45015: ld.elf_so: support ELF symbol versioning
Applied latest patch.

Add support for DF_1_BIND_NOW, DF_1_NODELETE and DF_1_NOOPEN marked
objects, and the RTLD_NODELETE and RTLD_NOLOAD flags to dlopen(3).

Mark libpthread as DF_1_NOOPEN and use it to test the functionality.

Somewhat taken from FreeBSD.

Fixes PR 42029.

OK from christos and joerg.

Typo in comment.

Add Solarisa-like dlinfo() interface to the ELF dynamic linker.
Implement RTLD_DI_LINKMAP which returns a pointer to the linkmap
chain at the given object. Other Solaris queries are currently
unimplemented.

branches: 1.19.8; 1.19.10; 1.19.16;
Remove clause 3 and 4 from TNF licenses

branches: 1.18.18;
Add restrict qualifiers to dlsym() (XSI) and dladdr() arguments.

branches: 1.17.2;
de-__P -- the hack is long since useless. Discussed with christos,
matt, kleink, others. Approved by christos.

Remove reference to dlinfo - it doesn't exist in NetBSD.

Add RTLD_SELF, RTLD_NEXT, RTLD_DEFAULT, from FreeBSD

Add a new feature-test macro, _NETBSD_SOURCE. If this is defined
by the application, all NetBSD interfaces are made visible, even
if some other feature-test macro (like _POSIX_C_SOURCE) is defined.
<sys/featuretest.h> defined _NETBSD_SOURCE if none of _ANSI_SOURCE,
_POSIX_C_SOURCE and _XOPEN_SOURCE is defined, so as to preserve
existing behaviour.

This has two major advantages:
+ Programs that require non-POSIX facilities but define _POSIX_C_SOURCE
can trivially be overruled by putting -D_NETBSD_SOURCE in their CFLAGS.
+ It makes most of the #ifs simpler, in that they're all now ORs of the
various macros, rather than having checks for (!defined(_ANSI_SOURCE) ||
!defined(_POSIX_C_SOURCE) || !defined(_XOPEN_SOURCE)) all over the place.

I've tried not to change the semantics of the headers in any case where
_NETBSD_SOURCE wasn't defined, but there were some places where the
current semantics were clearly mad, and retaining them was harder than
correcting them. In particular, I've mostly normalised things so that
_ANSI_SOURCE gets you the smallest set of stuff, then _POSIX_C_SOURCE,
_XOPEN_SOURCE and _NETBSD_SOURCE in that order.

Tested by building for vax, encouraged by thorpej, and uncontested in
tech-userlevel for a week.

branches: 1.13.6;
Remove 'extern' from function declarations.

branches: 1.12.2;
Const'ify dli_saddr in struct _dl_info.

change first argument of dladdr to const.

Declare dlerror()'s return value __aconst.

Assign my copyright to the TNF.

Change ld.so default behavior to RTLD_LOCAL, and make RTLD_LOCAL into a
new flag bit. Keep RTLD_GLOBAL as an actual flag bit so it won't be
re-used, or may be used for something later. Mask the dlopen() mode bits
in ld.elf_so so a comparison against RTLD_NOW works. (RTLD_{LOCAL,GLOBAL}
needs to be implemented for ld.elf_so.)

Add dladdr() and `Dl_info' structure; interface cloned from Solaris 2.

Per XSH98, define the RTLD_LOCAL flag. In this implementation it's a NOP,
since non-local searches have to be explicitly enabled via RTLD_GLOBAL.

Protect the dlctl() prototype and the DL_* macros against _XOPEN_SOURCE;
they are neither specified by the XPG nor part of the name space reserved for
implementation-defined use.

Define RTLD_GLOBAL.

Add `const' to dlopen() & dlsym() protos, per PR#2453.
Add RTLD_NOW.

{BEGIN,END}DECLS

Put dlopen() et.al. declarations in separate header file for compatibility.