Merge tag 'glibc-2.28' into baseline-2.28baseline

The GNU C Library
=================

The GNU C Library version 2.28 is now available.

The GNU C Library is used as *the* C library in the GNU system and
in GNU/Linux systems, as well as many other systems that use Linux
as the kernel.

The GNU C Library is primarily designed to be a portable
and high performance C library.  It follows all relevant
standards including ISO C11 and POSIX.1-2008.  It is also
internationalized and has one of the most complete
internationalization interfaces known.

The GNU C Library webpage is at http://www.gnu.org/software/libc/

Packages for the 2.28 release may be downloaded from:
        http://ftpmirror.gnu.org/libc/
        http://ftp.gnu.org/gnu/libc/

The mirror list is at http://www.gnu.org/order/ftp.html

NEWS for version 2.28
=====================

Major new features:

* The localization data for ISO 14651 is updated to match the 2016
  Edition 4 release of the standard, this matches data provided by
  Unicode 9.0.0.  This update introduces significant improvements to the
  collation of Unicode characters.  This release deviates slightly from
  the standard in that the collation element ordering for lowercase and
  uppercase LATIN script characters is adjusted to ensure that regular
  expressions with ranges like [a-z] and [A-Z] don't interleave e.g. A
  is not matched by [a-z].  With the update many locales have been
  updated to take advantage of the new collation information.  The new
  collation information has increased the size of the compiled locale
  archive or binary locales.

* The GNU C Library can now be compiled with support for Intel CET, AKA
  Intel Control-flow Enforcement Technology.  When the library is built
  with --enable-cet, the resulting glibc is protected with indirect
  branch tracking (IBT) and shadow stack (SHSTK).  CET-enabled glibc is
  compatible with all existing executables and shared libraries.  This
  feature is currently supported on i386, x86_64 and x32 with GCC 8 and
  binutils 2.29 or later.  Note that CET-enabled glibc requires CPUs
  capable of multi-byte NOPs, like x86-64 processors as well as Intel
  Pentium Pro or newer.  NOTE: --enable-cet has been tested for i686,
  x86_64 and x32 on non-CET processors.  --enable-cet has been tested
  for x86_64 and x32 on CET SDVs, but Intel CET support hasn't been
  validated for i686.

* The GNU C Library now has correct support for ABSOLUTE symbols
  (SHN_ABS-relative symbols).  Previously such ABSOLUTE symbols were
  relocated incorrectly or in some cases discarded.  The GNU linker can
  make use of the newer semantics, but it must communicate it to the
  dynamic loader by setting the ELF file's identification (EI_ABIVERSION
  field) to indicate such support is required.

* Unicode 11.0.0 Support: Character encoding, character type info, and
  transliteration tables are all updated to Unicode 11.0.0, using
  generator scripts contributed by Mike FABIAN (Red Hat).

* <math.h> functions that round their results to a narrower type are added
  from TS 18661-1:2014 and TS 18661-3:2015:

  - fadd, faddl, daddl and corresponding fMaddfN, fMaddfNx, fMxaddfN and
    fMxaddfNx functions.

  - fsub, fsubl, dsubl and corresponding fMsubfN, fMsubfNx, fMxsubfN and
    fMxsubfNx functions.

  - fmul, fmull, dmull and corresponding fMmulfN, fMmulfNx, fMxmulfN and
    fMxmulfNx functions.

  - fdiv, fdivl, ddivl and corresponding fMdivfN, fMdivfNx, fMxdivfN and
    fMxdivfNx functions.

* Two grammatical forms of month names are now supported for the following
  languages: Armenian, Asturian, Catalan, Czech, Kashubian, Occitan, Ossetian,
  Scottish Gaelic, Upper Sorbian, and Walloon.  The following languages now
  support two grammatical forms in abbreviated month names: Catalan, Greek,
  and Kashubian.

* Newly added locales: Lower Sorbian (dsb_DE) and Yakut (sah_RU) also
  include the support for two grammatical forms of month names.

* Building and running on GNU/Hurd systems now works without out-of-tree
  patches.

* The renameat2 function has been added, a variant of the renameat function
  which has a flags argument.  If the flags are zero, the renameat2 function
  acts like renameat.  If the flag is not zero and there is no kernel
  support for renameat2, the function will fail with an errno value of
  EINVAL.  This is different from the existing gnulib function renameatu,
  which performs a plain rename operation in case of a RENAME_NOREPLACE
  flags and a non-existing destination (and therefore has a race condition
  that can clobber the destination inadvertently).

* The statx function has been added, a variant of the fstatat64
  function with an additional flags argument.  If there is no direct
  kernel support for statx, glibc provides basic stat support based on
  the fstatat64 function.

* IDN domain names in getaddrinfo and getnameinfo now use the system libidn2
  library if installed.  libidn2 version 2.0.5 or later is recommended.  If
  libidn2 is not available, internationalized domain names are not encoded
  or decoded even if the AI_IDN or NI_IDN flags are passed to getaddrinfo or
  getnameinfo.  (getaddrinfo calls with non-ASCII names and AI_IDN will fail
  with an encoding error.)  Flags which used to change the IDN encoding and
  decoding behavior (AI_IDN_ALLOW_UNASSIGNED, AI_IDN_USE_STD3_ASCII_RULES,
  NI_IDN_ALLOW_UNASSIGNED, NI_IDN_USE_STD3_ASCII_RULES) have been
  deprecated.  They no longer have any effect.

* Parsing of dynamic string tokens in DT_RPATH, DT_RUNPATH, DT_NEEDED,
  DT_AUXILIARY, and DT_FILTER has been expanded to support the full
  range of ELF gABI expressions including such constructs as
  '$ORIGIN$ORIGIN' (if valid).  For SUID/GUID applications the rules
  have been further restricted, and where in the past a dynamic string
  token sequence may have been interpreted as a literal string it will
  now cause a load failure.  These load failures were always considered
  unspecified behaviour from the perspective of the dynamic loader, and
  for safety are now load errors e.g. /foo/${ORIGIN}.so in DT_NEEDED
  results in a load failure now.

* Support for ISO C threads (ISO/IEC 9899:2011) has been added.  The
  implementation includes all the standard functions provided by
  <threads.h>:

  - thrd_current, thrd_equal, thrd_sleep, thrd_yield, thrd_create,
    thrd_detach, thrd_exit, and thrd_join for thread management.

  - mtx_init, mtx_lock, mtx_timedlock, mtx_trylock, mtx_unlock, and
    mtx_destroy for mutual exclusion.

  - call_once for function call synchronization.

  - cnd_broadcast, cnd_destroy, cnd_init, cnd_signal, cnd_timedwait, and
    cnd_wait for conditional variables.

  - tss_create, tss_delete, tss_get, and tss_set for thread-local storage.

  Application developers must link against libpthread to use ISO C threads.

Deprecated and removed features, and other changes affecting compatibility:

* The nonstandard header files <libio.h> and <_G_config.h> are no longer
  installed.  Software that was using either header should be updated to
  use standard <stdio.h> interfaces instead.

* The stdio functions 'getc' and 'putc' are no longer defined as macros.
  This was never required by the C standard, and the macros just expanded
  to call alternative names for the same functions.  If you hoped getc and
  putc would provide performance improvements over fgetc and fputc, instead
  investigate using (f)getc_unlocked and (f)putc_unlocked, and, if
  necessary, flockfile and funlockfile.

* All stdio functions now treat end-of-file as a sticky condition.  If you
  read from a file until EOF, and then the file is enlarged by another
  process, you must call clearerr or another function with the same effect
  (e.g. fseek, rewind) before you can read the additional data.  This
  corrects a longstanding C99 conformance bug.  It is most likely to affect
  programs that use stdio to read interactive input from a terminal.
  (Bug #1190.)

* The macros 'major', 'minor', and 'makedev' are now only available from
  the header <sys/sysmacros.h>; not from <sys/types.h> or various other
  headers that happen to include <sys/types.h>.  These macros are rarely
  used, not part of POSIX nor XSI, and their names frequently collide with
  user code; see https://sourceware.org/bugzilla/show_bug.cgi?id=19239 for
  further explanation.

  <sys/sysmacros.h> is a GNU extension.  Portable programs that require
  these macros should first include <sys/types.h>, and then include
  <sys/sysmacros.h> if __GNU_LIBRARY__ is defined.

* The tilegx*-*-linux-gnu configurations are no longer supported.

* The obsolete function ustat is no longer available to newly linked
  binaries; the headers <ustat.h> and <sys/ustat.h> have been removed.  This
  function has been deprecated in favor of fstatfs and statfs.

* The obsolete function nfsservctl is no longer available to newly linked
  binaries.  This function was specific to systems using the Linux kernel
  and could not usefully be used with the GNU C Library on systems with
  version 3.1 or later of the Linux kernel.

* The obsolete function name llseek is no longer available to newly linked
  binaries.  This function was specific to systems using the Linux kernel
  and was not declared in a header.  Programs should use the lseek64 name
  for this function instead.

* The AI_IDN_ALLOW_UNASSIGNED and NI_IDN_ALLOW_UNASSIGNED flags for the
  getaddrinfo and getnameinfo functions have been deprecated.  The behavior
  previously selected by them is now always enabled.

* The AI_IDN_USE_STD3_ASCII_RULES and NI_IDN_USE_STD3_ASCII_RULES flags for
  the getaddrinfo and getnameinfo functions have been deprecated.  The STD3
  restriction (rejecting '_' in host names, among other things) has been
  removed, for increased compatibility with non-IDN name resolution.

* The fcntl function now have a Long File Support variant named fcntl64.  It
  is added to fix some Linux Open File Description (OFD) locks usage on non
  LFS mode.  As for others *64 functions, fcntl64 semantics are analogous with
  fcntl and LFS support is handled transparently.  Also for Linux, the OFD
  locks act as a cancellation entrypoint.

* The obsolete functions encrypt, encrypt_r, setkey, setkey_r, cbc_crypt,
  ecb_crypt, and des_setparity are no longer available to newly linked
  binaries, and the headers <rpc/des_crypt.h> and <rpc/rpc_des.h> are no
  longer installed.  These functions encrypted and decrypted data with the
  DES block cipher, which is no longer considered secure.  Software that
  still uses these functions should switch to a modern cryptography library,
  such as libgcrypt.

* Reflecting the removal of the encrypt and setkey functions above, the
  macro _XOPEN_CRYPT is no longer defined.  As a consequence, the crypt
  function is no longer declared unless _DEFAULT_SOURCE or _GNU_SOURCE is
  enabled.

* The obsolete function fcrypt is no longer available to newly linked
  binaries.  It was just another name for the standard function crypt,
  and it has not appeared in any header file in many years.

* We have tentative plans to hand off maintenance of the passphrase-hashing
  library, libcrypt, to a separate development project that will, we hope,
  keep up better with new passphrase-hashing algorithms.  We will continue
  to declare 'crypt' in <unistd.h>, and programs that use 'crypt' or
  'crypt_r' should not need to change at all; however, distributions will
  need to install <crypt.h> and libcrypt from a separate project.

  In this release, if the configure option --disable-crypt is used, glibc
  will not install <crypt.h> or libcrypt, making room for the separate
  project's versions of these files.  The plan is to make this the default
  behavior in a future release.

Changes to build and runtime requirements:

  GNU make 4.0 or later is now required to build glibc.

Security related changes:

  CVE-2016-6261, CVE-2016-6263, CVE-2017-14062: Various vulnerabilities have
  been fixed by removing the glibc-internal IDNA implementation and using
  the system-provided libidn2 library instead.  Originally reported by Hanno
  Böck and Christian Weisgerber.

  CVE-2017-18269: An SSE2-based memmove implementation for the i386
  architecture could corrupt memory.  Reported by Max Horn.

  CVE-2018-11236: Very long pathname arguments to realpath function could
  result in an integer overflow and buffer overflow.  Reported by Alexey
  Izbyshev.

  CVE-2018-11237: The mempcpy implementation for the Intel Xeon Phi
  architecture could write beyond the target buffer, resulting in a buffer
  overflow.  Reported by Andreas Schwab.

The following bugs are resolved with this release:

  [1190] stdio: fgetc()/fread() behaviour is not POSIX compliant
  [6889] manual: 'PWD' mentioned but not specified
  [13575] libc: SSIZE_MAX defined as LONG_MAX is inconsistent with ssize_t,
    when __WORDSIZE != 64
  [13762] regex: re_search etc. should return -2 on memory exhaustion
  [13888] build: /tmp usage during testing
  [13932] math: dbl-64 pow unexpectedly slow for some inputs
  [14092] nptl: Support C11 threads
  [14095] localedata: Review / update collation data from Unicode / ISO
    14651
  [14508] libc: -Wformat warnings
  [14553] libc: Namespace pollution loff_t in sys/types.h
  [14890] libc: Make NT_PRFPREG canonical.
  [15105] libc: Extra PLT references with -Os
  [15512] libc: __bswap_constant_16 not compiled when -Werror -Wsign-
    conversion is given
  [16335] manual: Feature test macro documentation incomplete and out of
    date
  [16552] libc: Unify umount implementations in terms of umount2
  [17082] libc: htons et al.: statement-expressions prevent use on global
    scope with -O1 and higher
  [17343] libc: Signed integer overflow in /stdlib/random_r.c
  [17438] localedata: pt_BR: wrong d_fmt delimiter
  [17662] libc: please implement binding for the new renameat2 syscall
  [17721] libc: __restrict defined as /* Ignore */ even in c11
  [17979] libc: inconsistency between uchar.h and stdint.h
  [18018] dynamic-link: Additional $ORIGIN handling issues (CVE-2011-0536)
  [18023] libc: extend_alloca is broken (questionable pointer comparison,
    horrible machine code)
  [18124] libc: hppa: setcontext erroneously returns -1 as exit code for
    last constant.
  [18471] libc: llseek should be a compat symbol
  [18473] soft-fp: [powerpc-nofpu] __sqrtsf2, __sqrtdf2 should be compat
    symbols
  [18991] nss: nss_files skips large entry in database
  [19239] libc: Including stdlib.h ends up with macros major and minor being
    defined
  [19463] libc: linknamespace failures when compiled with -Os
  [19485] localedata: csb_PL: Update month translations + add yesstr/nostr
  [19527] locale: Normalized charset name not recognized by setlocale
  [19667] string: Missing Sanity Check for malloc calls in file 'testcopy.c'
  [19668] libc: Missing Sanity Check for malloc() in file 'tst-setcontext-
    fpscr.c'
  [19728] network: out of bounds stack read in libidn function
    idna_to_ascii_4i (CVE-2016-6261)
  [19729] network: out of bounds heap read on invalid utf-8 inputs in
    stringprep_utf8_nfkc_normalize (CVE-2016-6263)
  [19818] dynamic-link: Absolute (SHN_ABS) symbols incorrectly relocated by
    the base address
  [20079] libc: Add SHT_X86_64_UNWIND to elf.h
  [20251] libc: 32bit programs pass garbage in struct flock for OFD locks
  [20419] dynamic-link: files with large allocated notes crash in
    open_verify
  [20530] libc: bswap_16 should use __builtin_bswap16() when available
  [20890] dynamic-link: ldconfig: fsync the files before atomic rename
  [20980] manual: CFLAGS environment variable replaces vital options
  [21163] regex: Assertion failure in pop_fail_stack when executing a
    malformed regexp (CVE-2015-8985)
  [21234] manual: use of CFLAGS makes glibc detect no optimization
  [21269] dynamic-link: i386 sigaction sa_restorer handling is wrong
  [21313] build: Compile Error GCC 5.4.0 MIPS with -0S
  [21314] build: Compile Error GCC 5.2.0 MIPS with -0s
  [21508] locale: intl/tst-gettext failure with latest msgfmt
  [21547] localedata: Tibetan script collation broken (Dzongkha and Tibetan)
  [21812] network: getifaddrs() returns entries with ifa_name == NULL
  [21895] libc: ppc64 setjmp/longjmp not fully interoperable with static
    dlopen
  [21942] dynamic-link: _dl_dst_substitute incorrectly handles $ORIGIN: with
    AT_SECURE=1
  [22241] localedata: New locale: Yakut (Sakha) locale for Russia (sah_RU)
  [22247] network: Integer overflow in the decode_digit function in
    puny_decode.c in libidn (CVE-2017-14062)
  [22342] nscd: NSCD not properly caching netgroup
  [22391] nptl: Signal function clear NPTL internal symbols inconsistently
  [22550] localedata: es_ES locale (and  other es_* locales):  collation
    should treat ñ  as a primary different character,  sync the collation
    for Spanish with CLDR
  [22638] dynamic-link: sparc: static binaries are broken if glibc is built
    by gcc configured with --enable-default-pie
  [22639] time: year 2039 bug for localtime etc. on 64-bit platforms
  [22644] string: memmove-sse2-unaligned on 32bit x86 produces garbage when
    crossing 2GB threshold (CVE-2017-18269)
  [22646] localedata: redundant data (LC_TIME) for es_CL, es_CU, es_EC and
    es_BO
  [22735] time: Misleading typo in time.h source comment regarding
    CLOCKS_PER_SECOND
  [22753] libc: preadv2/pwritev2 fallback code should handle offset=-1
  [22761] libc: No trailing `%n' conversion specifier in FMT passed from
    `__assert_perror_fail ()' to `__assert_fail_base ()'
  [22766] libc: all glibc internal dlopen should use RTLD_NOW for robust
    dlopen failures
  [22786] libc: Stack buffer overflow in realpath() if input size is close
    to SSIZE_MAX (CVE-2018-11236)
  [22787] dynamic-link: _dl_check_caller returns false when libc is linked
    through an absolute DT_NEEDED path
  [22792] build: tcb-offsets.h dependency dropped
  [22797] libc: pkey_get() uses non-reserved name of argument
  [22807] libc: PTRACE_* constants missing for powerpc
  [22818] glob: posix/tst-glob_lstat_compat failure on alpha
  [22827] dynamic-link: RISC-V ELF64 parser mis-reads flag in ldconfig
  [22830] malloc: malloc_stats doesn't restore cancellation state on stderr
  [22848] localedata: ca_ES: update date definitions from CLDR
  [22862] build: _DEFAULT_SOURCE is defined even when _ISOC11_SOURCE is
  [22884] math: RISCV fmax/fmin handle signalling NANs incorrectly
  [22896] localedata: Update locale data for an_ES
  [22902] math: float128 test failures with GCC 8
  [22918] libc: multiple common of `__nss_shadow_database'
  [22919] libc: sparc32: backtrace yields infinite backtrace with
    makecontext
  [22926] libc: FTBFS on powerpcspe
  [22932] localedata: lt_LT: Update of abbreviated month names from CLDR
    required
  [22937] localedata: Greek (el_GR, el_CY) locales actually need ab_alt_mon
  [22947] libc: FAIL: misc/tst-preadvwritev2
  [22963] localedata: cs_CZ: Add alternative month names
  [22987] math: [powerpc/sparc] fdim inlines errno, exceptions handling
  [22996] localedata: change LC_PAPER to en_US in es_BO locale
  [22998] dynamic-link: execstack tests are disabled when SELinux is
    disabled
  [23005] network: Crash in __res_context_send after memory allocation
    failure
  [23007] math: strtod cannot handle -nan
  [23024] nss: getlogin_r is performing NSS lookups when loginid isn't set
  [23036] regex: regex equivalence class regression
  [23037] libc: initialize msg_flags to zero for sendmmsg() calls
  [23069] libc: sigaction broken on riscv64-linux-gnu
  [23094] localedata: hr_HR: wrong thousands_sep and mon_thousands_sep
  [23102] dynamic-link: Incorrect parsing of multiple consecutive $variable
    patterns in runpath entries (e.g. $ORIGIN$ORIGIN)
  [23137] nptl: s390: pthread_join sometimes block indefinitely (on 31bit
    and libc build with -Os)
  [23140] localedata: More languages need two forms of month names
  [23145] libc: _init/_fini aren't marked as hidden
  [23152] localedata: gd_GB: Fix typo in "May" (abbreviated)
  [23171] math: C++ iseqsig for long double converts arguments to double
  [23178] nscd: sudo will fail when it is run in concurrent with commands
    that changes /etc/passwd
  [23196] string: __mempcpy_avx512_no_vzeroupper mishandles large copies
    (CVE-2018-11237)
  [23206] dynamic-link: static-pie + dlopen breaks debugger interaction
  [23208] localedata: New locale - Lower Sorbian (dsb)
  [23233] regex: Memory leak in build_charclass_op function in file
    posix/regcomp.c
  [23236] stdio: Harden function pointers in _IO_str_fields
  [23250] nptl: Offset of __private_ss differs from GCC
  [23253] math: tgamma test suite failures on i686 with -march=x86-64
    -mtune=generic -mfpmath=sse
  [23259] dynamic-link: Unsubstituted ${ORIGIN} remains in DT_NEEDED for
    AT_SECURE
  [23264] libc: posix_spawnp wrongly executes ENOEXEC in non compat mode
  [23266] nis: stringop-truncation warning with new gcc8.1 in nisplus-
    parser.c
  [23272] math: fma(INFINITY,INFIITY,0.0) should be INFINITY
  [23277] math: nan function should not have const attribute
  [23279] math: scanf and strtod wrong for some hex floating-point
  [23280] math: wscanf rounds wrong; wcstod is ok for negative numbers and
    directed rounding
  [23290] localedata: IBM273 is not equivalent to ISO-8859-1
  [23303] build: undefined reference to symbol
    '__parse_hwcap_and_convert_at_platform@@GLIBC_2.23'
  [23307] dynamic-link: Absolute symbols whose value is zero ignored in
    lookup
  [23313] stdio: libio vtables validation and standard file object
    interposition
  [23329] libc: The __libc_freeres infrastructure is not properly run across
    DSO boundaries.
  [23349] libc: Various glibc headers no longer compatible with
    <linux/time.h>
  [23351] malloc: Remove unused code related to heap dumps and malloc
    checking
  [23363] stdio: stdio-common/tst-printf.c has non-free license
  [23396] regex: Regex equivalence regression in single-byte locales
  [23422] localedata: oc_FR: More updates of locale data
  [23442] build: New warning with GCC 8
  [23448] libc: Out of bounds access in IBM-1390 converter
  [23456] libc: Wrong index_cpu_LZCNT
  [23458] build: tst-get-cpu-features-static isn't added to tests
  [23459] libc: COMMON_CPUID_INDEX_80000001 isn't populated for Intel
    processors
  [23467] dynamic-link: x86/CET: A property note parser bug

Release Notes
=============

https://sourceware.org/glibc/wiki/Release/2.28

Contributors
============

This release was made possible by the contributions of many people.
The maintainers are grateful to everyone who has contributed
changes or bug reports.  These include:

Adhemerval Zanella
Agustina Arzille
Alan Modra
Alexandre Oliva
Amit Pawar
Andreas Schwab
Andrew Senkevich
Andrew Waterman
Aurelien Jarno
Carlos O'Donell
Chung-Lin Tang
DJ Delorie
Daniel Alvarez
David Michael
Dmitry V. Levin
Dragan Stanojevic - Nevidljivi
Florian Weimer
Flávio Cruz
Francois Goichon
Gabriel F. T. Gomes
H.J. Lu
Herman ten Brugge
Hongbo Zhang
Igor Gnatenko
Jesse Hathaway
John David Anglin
Joseph Myers
Leonardo Sandoval
Maciej W. Rozycki
Mark Wielaard
Martin Sebor
Michael Wolf
Mike FABIAN
Patrick McGehearty
Patsy Franklin
Paul Pluzhnikov
Quentin PAGÈS
Rafal Luzynski
Rajalakshmi Srinivasaraghavan
Raymond Nicholson
Rical Jasan
Richard Braun
Robert Buj
Rogerio Alves
Samuel Thibault
Sean McKean
Siddhesh Poyarekar
Stefan Liebler
Steve Ellcey
Sylvain Lesage
Szabolcs Nagy
Thomas Schwinge
Tulio Magno Quites Machado Filho
Valery Timiriliyev
Vincent Chen
Wilco Dijkstra
Zack Weinberg
Zong Li

1 files changed, 367 insertions, 0 deletions

diff --git a/include/alloc_buffer.h b/include/alloc_buffer.h
new file mode 100644
index 0000000000..e69ed66c8e
--- /dev/null
+++ b/include/alloc_buffer.h
@@ -0,0 +1,367 @@
+/* Allocation from a fixed-size buffer.
+   Copyright (C) 2017-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* Allocation buffers are used to carve out sub-allocations from a
+   larger allocation.  Their primary application is in writing NSS
+   modules, which receive a caller-allocated buffer in which they are
+   expected to store variable-length results:
+
+     void *buffer = ...;
+     size_t buffer_size = ...;
+
+     struct alloc_buffer buf = alloc_buffer_create (buffer, buffer_size);
+     result->gr_name = alloc_buffer_copy_string (&buf, name);
+
+     // Allocate a list of group_count groups and copy strings into it.
+     char **group_list = alloc_buffer_alloc_array
+       (&buf, char *, group_count  + 1);
+     if (group_list == NULL)
+       return ...; // Request a larger buffer.
+     for (int i = 0; i < group_count; ++i)
+       group_list[i] = alloc_buffer_copy_string (&buf, group_list_src[i]);
+     group_list[group_count] = NULL;
+     ...
+
+     if (alloc_buffer_has_failed (&buf))
+       return ...; // Request a larger buffer.
+     result->gr_mem = group_list;
+     ...
+
+   Note that it is not necessary to check the results of individual
+   allocation operations if the returned pointer is not dereferenced.
+   Allocation failure is sticky, so one check using
+   alloc_buffer_has_failed at the end covers all previous failures.
+
+   A different use case involves combining multiple heap allocations
+   into a single, large one.  In the following example, an array of
+   doubles and an array of ints is allocated:
+
+     size_t double_array_size = ...;
+     size_t int_array_size = ...;
+
+     void *heap_ptr;
+     struct alloc_buffer buf = alloc_buffer_allocate
+       (double_array_size * sizeof (double) + int_array_size * sizeof (int),
+        &heap_ptr);
+     _Static_assert (__alignof__ (double) >= __alignof__ (int),
+                     "no padding after double array");
+     double *double_array = alloc_buffer_alloc_array
+       (&buf, double, double_array_size);
+     int *int_array = alloc_buffer_alloc_array (&buf, int, int_array_size);
+     if (alloc_buffer_has_failed (&buf))
+       return ...; // Report error.
+     ...
+     free (heap_ptr);
+
+   The advantage over manual coding is that the computation of the
+   allocation size does not need an overflow check.  In case of an
+   overflow, one of the subsequent allocations from the buffer will
+   fail.  The initial size computation is checked for consistency at
+   run time, too.  */
+
+#ifndef _ALLOC_BUFFER_H
+#define _ALLOC_BUFFER_H
+
+#include <inttypes.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <sys/param.h>
+
+/* struct alloc_buffer objects refer to a region of bytes in memory of a
+   fixed size.  The functions below can be used to allocate single
+   objects and arrays from this memory region, or write to its end.
+   On allocation failure (or if an attempt to write beyond the end of
+   the buffer with one of the copy functions), the buffer enters a
+   failed state.
+
+   struct alloc_buffer objects can be copied.  The backing buffer will
+   be shared, but the current write position will be independent.
+
+   Conceptually, the memory region consists of a current write pointer
+   and a limit, beyond which the write pointer cannot move.  */
+struct alloc_buffer
+{
+  /* uintptr_t is used here to simplify the alignment code, and to
+     avoid issues undefined subtractions if the buffer covers more
+     than half of the address space (which would result in differences
+     which could not be represented as a ptrdiff_t value).  */
+  uintptr_t __alloc_buffer_current;
+  uintptr_t __alloc_buffer_end;
+};
+
+enum
+  {
+    /* The value for the __alloc_buffer_current member which marks the
+       buffer as invalid (together with a zero-length buffer).  */
+    __ALLOC_BUFFER_INVALID_POINTER = 0,
+  };
+
+/* Internal function.  Terminate the process using __libc_fatal.  */
+void __libc_alloc_buffer_create_failure (void *start, size_t size);
+
+/* Create a new allocation buffer.  The byte range from START to START
+   + SIZE - 1 must be valid, and the allocation buffer allocates
+   objects from that range.  If START is NULL (so that SIZE must be
+   0), the buffer is marked as failed immediately.  */
+static inline struct alloc_buffer
+alloc_buffer_create (void *start, size_t size)
+{
+  uintptr_t current = (uintptr_t) start;
+  uintptr_t end = (uintptr_t) start + size;
+  if (end < current)
+    __libc_alloc_buffer_create_failure (start, size);
+  return (struct alloc_buffer) { current, end };
+}
+
+/* Internal function.  See alloc_buffer_allocate below.  */
+struct alloc_buffer __libc_alloc_buffer_allocate (size_t size, void **pptr)
+  __attribute__ ((nonnull (2)));
+
+/* Allocate a buffer of SIZE bytes using malloc.  The returned buffer
+   is in a failed state if malloc fails.  *PPTR points to the start of
+   the buffer and can be used to free it later, after the returned
+   buffer has been freed.  */
+static __always_inline __attribute__ ((nonnull (2)))
+struct alloc_buffer alloc_buffer_allocate (size_t size, void **pptr)
+{
+  return __libc_alloc_buffer_allocate (size, pptr);
+}
+
+/* Mark the buffer as failed.  */
+static inline void __attribute__ ((nonnull (1)))
+alloc_buffer_mark_failed (struct alloc_buffer *buf)
+{
+  buf->__alloc_buffer_current = __ALLOC_BUFFER_INVALID_POINTER;
+  buf->__alloc_buffer_end = __ALLOC_BUFFER_INVALID_POINTER;
+}
+
+/* Return the remaining number of bytes in the buffer.  */
+static __always_inline __attribute__ ((nonnull (1))) size_t
+alloc_buffer_size (const struct alloc_buffer *buf)
+{
+  return buf->__alloc_buffer_end - buf->__alloc_buffer_current;
+}
+
+/* Return true if the buffer has been marked as failed.  */
+static inline bool __attribute__ ((nonnull (1)))
+alloc_buffer_has_failed (const struct alloc_buffer *buf)
+{
+  return buf->__alloc_buffer_current == __ALLOC_BUFFER_INVALID_POINTER;
+}
+
+/* Add a single byte to the buffer (consuming the space for this
+   byte).  Mark the buffer as failed if there is not enough room.  */
+static inline void __attribute__ ((nonnull (1)))
+alloc_buffer_add_byte (struct alloc_buffer *buf, unsigned char b)
+{
+  if (__glibc_likely (buf->__alloc_buffer_current < buf->__alloc_buffer_end))
+    {
+      *(unsigned char *) buf->__alloc_buffer_current = b;
+      ++buf->__alloc_buffer_current;
+    }
+  else
+    alloc_buffer_mark_failed (buf);
+}
+
+/* Obtain a pointer to LENGTH bytes in BUF, and consume these bytes.
+   NULL is returned if there is not enough room, and the buffer is
+   marked as failed, or if the buffer has already failed.
+   (Zero-length allocations from an empty buffer which has not yet
+   failed succeed.)  */
+static inline __attribute__ ((nonnull (1))) void *
+alloc_buffer_alloc_bytes (struct alloc_buffer *buf, size_t length)
+{
+  if (length <= alloc_buffer_size (buf))
+    {
+      void *result = (void *) buf->__alloc_buffer_current;
+      buf->__alloc_buffer_current += length;
+      return result;
+    }
+  else
+    {
+      alloc_buffer_mark_failed (buf);
+      return NULL;
+    }
+}
+
+/* Internal function.  Statically assert that the type size is
+   constant and valid.  */
+static __always_inline size_t
+__alloc_buffer_assert_size (size_t size)
+{
+  if (!__builtin_constant_p (size))
+    {
+      __errordecl (error, "type size is not constant");
+      error ();
+    }
+  else if (size == 0)
+    {
+      __errordecl (error, "type size is zero");
+      error ();
+    }
+  return size;
+}
+
+/* Internal function.  Statically assert that the type alignment is
+   constant and valid.  */
+static __always_inline size_t
+__alloc_buffer_assert_align (size_t align)
+{
+  if (!__builtin_constant_p (align))
+    {
+      __errordecl (error, "type alignment is not constant");
+      error ();
+    }
+  else if (align == 0)
+    {
+      __errordecl (error, "type alignment is zero");
+      error ();
+    }
+  else if (!powerof2 (align))
+    {
+      __errordecl (error, "type alignment is not a power of two");
+      error ();
+    }
+  return align;
+}
+
+/* Internal function.  Obtain a pointer to an object.  */
+static inline __attribute__ ((nonnull (1))) void *
+__alloc_buffer_alloc (struct alloc_buffer *buf, size_t size, size_t align)
+{
+  if (size == 1 && align == 1)
+    return alloc_buffer_alloc_bytes (buf, size);
+
+  size_t current = buf->__alloc_buffer_current;
+  size_t aligned = roundup (current, align);
+  size_t new_current = aligned + size;
+  if (aligned >= current        /* No overflow in align step.  */
+      && new_current >= size    /* No overflow in size computation.  */
+      && new_current <= buf->__alloc_buffer_end) /* Room in buffer.  */
+    {
+      buf->__alloc_buffer_current = new_current;
+      return (void *) aligned;
+    }
+  else
+    {
+      alloc_buffer_mark_failed (buf);
+      return NULL;
+    }
+}
+
+/* Obtain a TYPE * pointer to an object in BUF of TYPE.  Consume these
+   bytes from the buffer.  Return NULL and mark the buffer as failed
+   if there is not enough room in the buffer, or if the buffer has
+   failed before.  */
+#define alloc_buffer_alloc(buf, type)				\
+  ((type *) __alloc_buffer_alloc				\
+   (buf, __alloc_buffer_assert_size (sizeof (type)),		\
+    __alloc_buffer_assert_align (__alignof__ (type))))
+
+/* Internal function.  Obtain a pointer to an object which is
+   subsequently added.  */
+static inline const __attribute__ ((nonnull (1))) void *
+__alloc_buffer_next (struct alloc_buffer *buf, size_t align)
+{
+  if (align == 1)
+    return (const void *) buf->__alloc_buffer_current;
+
+  size_t current = buf->__alloc_buffer_current;
+  size_t aligned = roundup (current, align);
+  if (aligned >= current        /* No overflow in align step.  */
+      && aligned <= buf->__alloc_buffer_end) /* Room in buffer.  */
+    {
+      buf->__alloc_buffer_current = aligned;
+      return (const void *) aligned;
+    }
+  else
+    {
+      alloc_buffer_mark_failed (buf);
+      return NULL;
+    }
+}
+
+/* Like alloc_buffer_alloc, but do not advance the pointer beyond the
+   object (so a subseqent call to alloc_buffer_next or
+   alloc_buffer_alloc returns the same pointer).  Note that the buffer
+   is still aligned according to the requirements of TYPE.  The effect
+   of this function is similar to allocating a zero-length array from
+   the buffer.  */
+#define alloc_buffer_next(buf, type)				\
+  ((const type *) __alloc_buffer_next				\
+   (buf, __alloc_buffer_assert_align (__alignof__ (type))))
+
+/* Internal function.  Allocate an array.  */
+void * __libc_alloc_buffer_alloc_array (struct alloc_buffer *buf,
+					size_t size, size_t align,
+					size_t count)
+  __attribute__ ((nonnull (1)));
+
+/* Obtain a TYPE * pointer to an array of COUNT objects in BUF of
+   TYPE.  Consume these bytes from the buffer.  Return NULL and mark
+   the buffer as failed if there is not enough room in the buffer,
+   or if the buffer has failed before.  (Zero-length allocations from
+   an empty buffer which has not yet failed succeed.)  */
+#define alloc_buffer_alloc_array(buf, type, count)       \
+  ((type *) __libc_alloc_buffer_alloc_array		 \
+   (buf, __alloc_buffer_assert_size (sizeof (type)),	 \
+    __alloc_buffer_assert_align (__alignof__ (type)),	 \
+    count))
+
+/* Internal function.  See alloc_buffer_copy_bytes below.  */
+struct alloc_buffer __libc_alloc_buffer_copy_bytes (struct alloc_buffer,
+						    const void *, size_t)
+  __attribute__ ((nonnull (2)));
+
+/* Copy SIZE bytes starting at SRC into the buffer.  If there is not
+   enough room in the buffer, the buffer is marked as failed.  No
+   alignment of the buffer is performed.  */
+static inline __attribute__ ((nonnull (1, 2))) void
+alloc_buffer_copy_bytes (struct alloc_buffer *buf, const void *src, size_t size)
+{
+  *buf = __libc_alloc_buffer_copy_bytes (*buf, src, size);
+}
+
+/* Internal function.  See alloc_buffer_copy_string below.  */
+struct alloc_buffer __libc_alloc_buffer_copy_string (struct alloc_buffer,
+						     const char *)
+  __attribute__ ((nonnull (2)));
+
+/* Copy the string at SRC into the buffer, including its null
+   terminator.  If there is not enough room in the buffer, the buffer
+   is marked as failed.  Return a pointer to the string.  */
+static inline __attribute__ ((nonnull (1, 2))) char *
+alloc_buffer_copy_string (struct alloc_buffer *buf, const char *src)
+{
+  char *result = (char *) buf->__alloc_buffer_current;
+  *buf = __libc_alloc_buffer_copy_string (*buf, src);
+  if (alloc_buffer_has_failed (buf))
+    result = NULL;
+  return result;
+}
+
+#ifndef _ISOMAC
+libc_hidden_proto (__libc_alloc_buffer_alloc_array)
+libc_hidden_proto (__libc_alloc_buffer_allocate)
+libc_hidden_proto (__libc_alloc_buffer_copy_bytes)
+libc_hidden_proto (__libc_alloc_buffer_copy_string)
+libc_hidden_proto (__libc_alloc_buffer_create_failure)
+#endif
+
+#endif /* _ALLOC_BUFFER_H */