vfprintf is entangled with vfwprintf (of course), __printf_fp,
__printf_fphex, __vstrfmon_l_internal, and the strfrom family of
functions.  The latter use the internal snprintf functionality,
so vsnprintf is converted as well.

The simples conversion is __printf_fphex, followed by
__vstrfmon_l_internal and __printf_fp, and finally
__vfprintf_internal and __vfwprintf_internal.  __vsnprintf_internal
and strfrom* are mostly consuming the new interfaces, so they
are comparatively simple.

__printf_fp is a public symbol, so the FILE *-based interface
had to preserved.

The __printf_fp rewrite does not change the actual binary-to-decimal
conversion algorithm, and digits are still not emitted directly to
the target buffer.  However, the staging buffer now uses bytes
instead of wide characters, and one buffer copy is eliminated.

The changes are at least performance-neutral in my testing.
Floating point printing and snprintf improved measurably, so that
this Lua script

  for i=1,5000000 do
      print(i, i * math.pi)
  end

runs about 5% faster for me.  To preserve fprintf performance for
a simple "%d" format, this commit has some logic changes under
LABEL (unsigned_number) to avoid additional function calls.  There
are certainly some very easy performance improvements here: binary,
octal and hexadecimal formatting can easily avoid the temporary work
buffer (the number of digits can be computed ahead-of-time using one
of the __builtin_clz* built-ins). Decimal formatting can use a
specialized version of _itoa_word for base 10.

The existing (inconsistent) width handling between strfmon and printf
is preserved here.  __print_fp_buffer_1 would have to use
__translated_number_width to achieve ISO conformance for printf.

Test expectations in libio/tst-vtables-common.c are adjusted because
the internal staging buffer merges all virtual function calls into
one.

In general, stack buffer usage is greatly reduced, particularly for
unbuffered input streams.  __printf_fp can still use a large buffer
in binary128 mode for %g, though.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

This function will be used to compute the width of a number
after i18n digit translation.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

And __wprintf_function_invoke.  These functions will be used to
to call registered printf specifier callbacks on printf buffers
after vfprintf and vfwprintf have been converted to buffers.  The new
implementation avoids alloca/variable length arrays.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

The type does not depend on wide vs narrow preprocessor macros,
so it does not need to be customized in stdio-common/printf-parse.h.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

Add  __printf_arginfo_table, __printf_function_table,
__printf_va_arg_table, __register_printf_specifier to
include/printf.h.

Improve the commentary to aid future developers who will stumble
upon this novel, yet not always perfect, mechanism to support
alternative formats for long double.

Likewise, rename __LONG_DOUBLE_USES_FLOAT128 to
__LDOUBLE_REDIRECTS_TO_FLOAT128_ABI now that development work
has settled down.  The command used was

git grep -l __LONG_DOUBLE_USES_FLOAT128 ':!./ChangeLog*' | \
  xargs sed -i 's/__LONG_DOUBLE_USES_FLOAT128/__LDOUBLE_REDIRECTS_TO_FLOAT128_ABI/g'

Reviewed-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>

GCC 9 has a bug (PR90731) whereby __typeof does not correctly copy
exception specifiers[1].  Surprisingly, this can be quieted by declaring
"#pragma system_header", or if the headers are installed in a system
directory.

Work around this by using the pragma for any gcc version between
9.0 and 9.2 to ensure tests continue to compile.

[1] Example error from g++ 9.2.1:

In file included from ../include/sys/cdefs.h:3,
                 from ../include/features.h:465,
                 from ../bits/libc-header-start.h:33,
                 from ../math/math.h:27,
                 from ../include/math.h:7,
                 from test-math-isinff.cc:21:
../libio/bits/stdio-ldbl.h:25:20: error: declaration of ‘int sprintf(char*, const char*, ...)’ has a different exception specifier
   25 | __LDBL_REDIR_DECL (sprintf)
      |                    ^~~~~~~
../misc/sys/cdefs.h:461:26: note: in definition of macro ‘__LDBL_REDIR_DECL’
  461 |   extern __typeof (name) name __asm (__ASMNAME ("__" #name "ieee128"));
      |                          ^~~~
In file included from ../include/stdio.h:5,
                 from test-math-isinff.cc:22:
../libio/stdio.h:334:12: note: from previous declaration ‘int sprintf(char*, const char*, ...) throw ()’
  334 | extern int sprintf (char *__restrict __s,
      |            ^~~~~~~

Reviewed-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>

Hide internal printf functions to allow direct access within libc.so and
libc.a without using GOT nor PLT.

Since __guess_grouping has been changed to take 2 arguments by

commit a1d84548c8aa7023cd039c85f81b831eef6d4a4c
Author: Ulrich Drepper <drepper@redhat.com>
Date:   Fri Feb 11 18:50:36 2000 +0000

the third argument passed to __guess_grouping is removed.

	[BZ #18822]
	[BZ #21986]
	* include/printf.h (__printf_fphex): Add attribute_hidden.
	(__guess_grouping): New prototype.
	* stdio-common/printf_fp.c (__guess_grouping): Removed.
	* stdio-common/reg-printf.c (__register_printf_specifier): Add
	libc_hidden_proto and libc_hidden_def.
	* stdlib/strfmon_l.c (__guess_grouping): Removed.
	(__vstrfmon_l): Remove the third argument passed to
	__guess_grouping.

xlocale.h is already a single-type micro-header, defining struct
__locale_struct and the typedefs __locale_t and locale_t.  This patch
brings it into the bits/types/ scheme: there are now
bits/types/__locale_t.h which defines only __locale_struct and
__locale_t, and bits/types/locale_t.h which defines locale_t as well
as the other two.  None of *our* headers need __locale_t.h, but it
appears to me that libstdc++ could make use of it.

There are a lot of external uses of xlocale.h, but all the uses I
checked had an autoconf test or equivalent for its existence.  It has
never been available from other C libraries, and it has always
contained a comment reading "This file is not standardized, don't rely
on it, it can go away without warning" so I think dropping it is
pretty safe.

I also took the opportunity to clean up comments in various public
header files that still talk about the *_l interfaces as though they
were completely nonstandard.  There are a few of them, notably the
strtoX_l and wcstoX_l families, that haven't been standardized, but
the bulk are in POSIX.1-2008.

        * locale/xlocale.h: Rename to...
	* locale/bits/types/__locale_t.h: ...here.  Adjust commentary.
	Only define struct __locale_struct and __locale_t, not locale_t.
        * locale/bits/types/locale_t.h: New file; define locale_t here.
        * locale/Makefile (headers): Update to match.

        * include/xlocale.h: Delete wrapper.
        * include/bits/types/__locale_t.h: New wrapper.
        * include/bits/types/locale_t.h: New wrapper.

        * ctype/ctype.h, include/printf.h, include/time.h
        * locale/langinfo.h, locale/locale.h, stdlib/monetary.h
        * stdlib/stdlib.h, string/string.h, string/strings.h, time/time.h
        * wcsmbs/wchar.h, wctype/wctype.h: Use bits/types/locale_t.h.
        Correct outdated comments regarding the standardization status of
        the functions that take locale_t arguments.

        * stdlib/strtod_l.c, stdlib/strtof_l.c, stdlib/strtol_l.c
        * stdlib/strtold_l.c, stdlib/strtoul_l.c, stdlib/strtoull_l.c
        * sysdeps/ieee754/ldbl-128ibm/strtold_l.c
        * sysdeps/ieee754/ldbl-64-128/strtold_l.c
        * wcsmbs/wcstod.c, wcsmbs/wcstod_l.c, wcsmbs/wcstof.c
        * wcsmbs/wcstof_l.c, wcsmbs/wcstold.c, wcsmbs/wcstold_l.c:
        Don't include xlocale.h. If necessary, include locale.h instead.

        * stdlib/strtold_l.c: Unconditionally include wchar.h.

This adds a test to ensure that the problems fixed in the last several
patches do not recur.  Each directory checks the headers that it
installs for two properties: first, each header must be compilable in
isolation, as both C and C++, under a representative combination of
language and library conformance levels; second, there is a blacklist
of identifiers that may not appear in any installed header, currently
consisting of the legacy BSD typedefs.  (There is an exemption for the
headers that define those typedefs, and for the RPC headers.  It may be
necessary to make this more sophisticated if we add more stuff to the
blacklist in the future.)

In order for this test to work correctly, every wrapper header
that actually defines something must guard those definitions with
 #ifndef _ISOMAC.  This is the existing mechanism used by the conform/
tests to tell wrapper headers not to define anything that the public
header wouldn't, and not to use anything from libc-symbols.h.  conform/
only cares for headers that we need to check for standards conformance,
whereas this test applies to *every* header.  (Headers in include/ that
are either installed directly, or are internal-use-only and do *not*
correspond to any installed header, are not affected.)

	* scripts/check-installed-headers.sh: New script.
	* Rules: In each directory that defines header files to be installed,
	run check-installed-headers.sh on them as a special test.
	* Makefile: Likewise for the headers installed at top level.

	* include/aliases.h, include/alloca.h, include/argz.h
	* include/arpa/nameser.h, include/arpa/nameser_compat.h
	* include/elf.h, include/envz.h, include/err.h
	* include/execinfo.h, include/fpu_control.h, include/getopt.h
	* include/gshadow.h, include/ifaddrs.h, include/libintl.h
	* include/link.h, include/malloc.h, include/mcheck.h
	* include/mntent.h, include/netinet/ether.h
	* include/nss.h, include/obstack.h, include/printf.h
	* include/pty.h, include/resolv.h, include/rpc/auth.h
	* include/rpc/auth_des.h, include/rpc/auth_unix.h
	* include/rpc/clnt.h, include/rpc/des_crypt.h
	* include/rpc/key_prot.h, include/rpc/netdb.h
	* include/rpc/pmap_clnt.h, include/rpc/pmap_prot.h
	* include/rpc/pmap_rmt.h, include/rpc/rpc.h
	* include/rpc/rpc_msg.h, include/rpc/svc.h
	* include/rpc/svc_auth.h, include/rpc/xdr.h
	* include/rpcsvc/nis_callback.h, include/rpcsvc/nislib.h
	* include/rpcsvc/yp.h, include/rpcsvc/ypclnt.h
	* include/rpcsvc/ypupd.h, include/shadow.h
	* include/stdio_ext.h, include/sys/epoll.h
	* include/sys/file.h, include/sys/gmon.h, include/sys/ioctl.h
	* include/sys/prctl.h, include/sys/profil.h
	* include/sys/statfs.h, include/sys/sysctl.h
	* include/sys/sysinfo.h, include/ttyent.h, include/utmp.h
	* sysdeps/arm/nacl/include/bits/setjmp.h
	* sysdeps/mips/include/sys/asm.h
	* sysdeps/unix/sysv/linux/include/sys/sysinfo.h
	* sysdeps/unix/sysv/linux/include/sys/timex.h
	* sysdeps/x86/fpu/include/bits/fenv.h:
	Add #ifndef _ISOMAC guard around internal declarations.
	Add multiple-inclusion guard if not already present.