The GNU C Library
=================
The GNU C Library version 2.25 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 2.25 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 2.25
=====================
* The feature test macro __STDC_WANT_LIB_EXT2__, from ISO/IEC TR
24731-2:2010, is supported to enable declarations of functions from that
TR. Note that not all functions from that TR are supported by the GNU C
Library.
* The feature test macro __STDC_WANT_IEC_60559_BFP_EXT__, from ISO/IEC TS
18661-1:2014, is supported to enable declarations of functions and macros
from that TS. Note that not all features from that TS are supported by
the GNU C Library.
* The feature test macro __STDC_WANT_IEC_60559_FUNCS_EXT__, from ISO/IEC TS
18661-4:2015, is supported to enable declarations of functions and macros
from that TS. Note that most features from that TS are not supported by
the GNU C Library.
* The nonstandard feature selection macros _REENTRANT and _THREAD_SAFE are
now treated as compatibility synonyms for _POSIX_C_SOURCE=199506L.
Since the GNU C Library defaults to a much newer revision of POSIX, this
will only affect programs that specifically request an old conformance
mode. For instance, a program compiled with -std=c89 -D_REENTRANT will
see a change in the visible declarations, but a program compiled with
just -D_REENTRANT, or -std=c99 -D_POSIX_C_SOURCE=200809L -D_REENTRANT,
will not.
Some C libraries once required _REENTRANT and/or _THREAD_SAFE to be
defined by all multithreaded code, but glibc has not required this for
many years.
* The inclusion of <sys/sysmacros.h> by <sys/types.h> is deprecated. This
means that in a future release, the macros “major”, “minor”, and “makedev”
will only be available from <sys/sysmacros.h>.
These macros are not part of POSIX nor XSI, and their names frequently
collide with user code; see for instance glibc bug 19239 and Red Hat bug
130601. <stdlib.h> includes <sys/types.h> under _GNU_SOURCE, and C++ code
presently cannot avoid being compiled under _GNU_SOURCE, exacerbating the
problem.
* New <fenv.h> features from TS 18661-1:2014 are added to libm: the
fesetexcept, fetestexceptflag, fegetmode and fesetmode functions, the
femode_t type and the FE_DFL_MODE and FE_SNANS_ALWAYS_SIGNAL macros.
* Integer width macros from TS 18661-1:2014 are added to <limits.h>:
CHAR_WIDTH, SCHAR_WIDTH, UCHAR_WIDTH, SHRT_WIDTH, USHRT_WIDTH, INT_WIDTH,
UINT_WIDTH, LONG_WIDTH, ULONG_WIDTH, LLONG_WIDTH, ULLONG_WIDTH; and to
<stdint.h>: INT8_WIDTH, UINT8_WIDTH, INT16_WIDTH, UINT16_WIDTH,
INT32_WIDTH, UINT32_WIDTH, INT64_WIDTH, UINT64_WIDTH, INT_LEAST8_WIDTH,
UINT_LEAST8_WIDTH, INT_LEAST16_WIDTH, UINT_LEAST16_WIDTH,
INT_LEAST32_WIDTH, UINT_LEAST32_WIDTH, INT_LEAST64_WIDTH,
UINT_LEAST64_WIDTH, INT_FAST8_WIDTH, UINT_FAST8_WIDTH, INT_FAST16_WIDTH,
UINT_FAST16_WIDTH, INT_FAST32_WIDTH, UINT_FAST32_WIDTH, INT_FAST64_WIDTH,
UINT_FAST64_WIDTH, INTPTR_WIDTH, UINTPTR_WIDTH, INTMAX_WIDTH,
UINTMAX_WIDTH, PTRDIFF_WIDTH, SIG_ATOMIC_WIDTH, SIZE_WIDTH, WCHAR_WIDTH,
WINT_WIDTH.
* New <math.h> features are added from TS 18661-1:2014:
- Signaling NaN macros: SNANF, SNAN, SNANL.
- Nearest integer functions: roundeven, roundevenf, roundevenl, fromfp,
fromfpf, fromfpl, ufromfp, ufromfpf, ufromfpl, fromfpx, fromfpxf,
fromfpxl, ufromfpx, ufromfpxf, ufromfpxl.
- llogb functions: the llogb, llogbf and llogbl functions, and the
FP_LLOGB0 and FP_LLOGBNAN macros.
- Max-min magnitude functions: fmaxmag, fmaxmagf, fmaxmagl, fminmag,
fminmagf, fminmagl.
- Comparison macros: iseqsig.
- Classification macros: iscanonical, issubnormal, iszero.
- Total order functions: totalorder, totalorderf, totalorderl,
totalordermag, totalordermagf, totalordermagl.
- Canonicalize functions: canonicalize, canonicalizef, canonicalizel.
- NaN functions: getpayload, getpayloadf, getpayloadl, setpayload,
setpayloadf, setpayloadl, setpayloadsig, setpayloadsigf, setpayloadsigl.
* The functions strfromd, strfromf, and strfroml, from ISO/IEC TS 18661-1:2014,
are added to libc. They convert a floating-point number into string.
* Most of glibc can now be built with the stack smashing protector enabled.
It is recommended to build glibc with --enable-stack-protector=strong.
Implemented by Nick Alcock (Oracle).
* The function explicit_bzero, from OpenBSD, has been added to libc. It is
intended to be used instead of memset() to erase sensitive data after use;
the compiler will not optimize out calls to explicit_bzero even if they
are "unnecessary" (in the sense that no _correct_ program can observe the
effects of the memory clear).
* On ColdFire, MicroBlaze, Nios II and SH3, the float_t type is now defined
to float instead of double. This does not affect the ABI of any libraries
that are part of the GNU C Library, but may affect the ABI of other
libraries that use this type in their interfaces.
* On x86_64, when compiling with -mfpmath=387 or -mfpmath=sse+387, the
float_t and double_t types are now defined to long double instead of float
and double. These options are not the default, and this does not affect
the ABI of any libraries that are part of the GNU C Library, but it may
affect the ABI of other libraries that use this type in their interfaces,
if they are compiled or used with those options.
* The getentropy and getrandom functions, and the <sys/random.h> header file
have been added.
* The buffer size for byte-oriented stdio streams is now limited to 8192
bytes by default. Previously, on Linux, the default buffer size on most
file systems was 4096 bytes (and thus remains unchanged), except on
network file systems, where the buffer size was unpredictable and could be
as large as several megabytes.
* The <sys/quota.h> header now includes the <linux/quota.h> header. Support
for the Linux quota interface which predates kernel version 2.4.22 has
been removed.
* The malloc_get_state and malloc_set_state functions have been removed.
Already-existing binaries that dynamically link to these functions will
get a hidden implementation in which malloc_get_state is a stub. As far
as we know, these functions are used only by GNU Emacs and this change
will not adversely affect already-built Emacs executables. Any undumped
Emacs executables, which normally exist only during an Emacs build, should
be rebuilt by re-running “./configure; make” in the Emacs build tree.
* The “ip6-dotint” and “no-ip6-dotint” resolver options, and the
corresponding RES_NOIP6DOTINT flag from <resolv.h> have been removed.
“no-ip6-dotint” had already been the default, and support for the
“ip6-dotint” option was removed from the Internet in 2006.
* The "ip6-bytestring" resolver option and the corresponding RES_USEBSTRING
flag from <resolv.h> have been removed. The option relied on a
backwards-incompatible DNS extension which was never deployed on the
Internet.
* The flags RES_AAONLY, RES_PRIMARY, RES_NOCHECKNAME, RES_KEEPTSIG,
RES_BLAST defined in the <resolv.h> header file have been deprecated.
They were already unimplemented.
* The "inet6" option in /etc/resolv.conf and the RES_USE_INET6 flag for
_res.flags are deprecated. The flag was standardized in RFC 2133, but
removed again from the IETF name lookup interface specification in RFC
2553. Applications should use getaddrinfo instead.
* DNSSEC-related declarations and definitions have been removed from the
<arpa/nameser.h> header file, and libresolv will no longer attempt to
decode the data part of DNSSEC record types. Previous versions of glibc
only implemented minimal support for the previous version of DNSSEC, which
is incompatible with the currently deployed version.
* The resource record type classification macros ns_t_qt_p, ns_t_mrr_p,
ns_t_rr_p, ns_t_udp_p, ns_t_xfr_p have been removed from the
<arpa/nameser.h> header file because the distinction between RR types and
meta-RR types is not officially standardized, subject to revision, and
thus not suitable for encoding in a macro.
* The types res_sendhookact, res_send_qhook, re_send_rhook, and the qhook
and rhook members of the res_state type in <resolv.h> have been removed.
The glibc stub resolver did not support these hooks, but the header file
did not reflect that.
* For multi-arch support it is recommended to use a GCC which has
been built with support for GNU indirect functions. This ensures
that correct debugging information is generated for functions
selected by IFUNC resolvers. This support can either be enabled by
configuring GCC with '--enable-gnu-indirect-function', or by
enabling it by default by setting 'default_gnu_indirect_function'
variable for a particular architecture in the GCC source file
'gcc/config.gcc'.
* GDB pretty printers have been added for mutex and condition variable
structures in POSIX Threads. When installed and loaded in gdb these pretty
printers show various pthread variables in human-readable form when read
using the 'print' or 'display' commands in gdb.
* Tunables feature added to allow tweaking of the runtime for an application
program. This feature can be enabled with the '--enable-tunables' configure
flag. The GNU C Library manual has details on usage and README.tunables has
instructions on adding new tunables to the library.
* A new version of condition variables functions have been implemented in
the NPTL implementation of POSIX Threads to provide stronger ordering
guarantees.
* A new version of pthread_rwlock functions have been implemented to use a more
scalable algorithm primarily through not using a critical section anymore to
make state changes.
Security related changes:
* On ARM EABI (32-bit), generating a backtrace for execution contexts which
have been created with makecontext could fail to terminate due to a
missing .cantunwind annotation. This has been observed to lead to a hang
(denial of service) in some Go applications compiled with gccgo. Reported
by Andreas Schwab. (CVE-2016-6323)
* The DNS stub resolver functions would crash due to a NULL pointer
dereference when processing a query with a valid DNS question type which
was used internally in the implementation. The stub resolver now uses a
question type which is outside the range of valid question type values.
(CVE-2015-5180)
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
Alan Modra
Alexandre Oliva
Andreas Schwab
Andrew Senkevich
Aurelien Jarno
Brent W. Baccala
Carlos O'Donell
Chris Metcalf
Chung-Lin Tang
DJ Delorie
David S. Miller
Denis Kaganovich
Dmitry V. Levin
Ernestas Kulik
Florian Weimer
Gabriel F T Gomes
Gabriel F. T. Gomes
H.J. Lu
Jakub Jelinek
James Clarke
James Greenhalgh
Jim Meyering
John David Anglin
Joseph Myers
Maciej W. Rozycki
Mark Wielaard
Martin Galvan
Martin Pitt
Mike Frysinger
Märt Põder
Nick Alcock
Paul E. Murphy
Paul Murphy
Rajalakshmi Srinivasaraghavan
Rasmus Villemoes
Rical Jasan
Richard Henderson
Roland McGrath
Samuel Thibault
Siddhesh Poyarekar
Stefan Liebler
Steve Ellcey
Svante Signell
Szabolcs Nagy
Tom Tromey
Torvald Riegel
Tulio Magno Quites Machado Filho
Wilco Dijkstra
Yury Norov
Zack Weinberg