GNU implementation of the standard C library
The
GNU C Library
, commonly known as
glibc
, is the
GNU Project
implementation of the
C standard library
. It is a wrapper around the system calls of the
Linux kernel
for application use. Despite its name, it now also directly supports
C++
(and, indirectly, other
programming languages
). It was started in the 1980s by the
Free Software Foundation
(FSF) for the
GNU
operating system.
glibc is
free software
released under the
GNU Lesser General Public License
.
[3]
The GNU C Library project provides the core libraries for the GNU system, as well as many systems that use
Linux
as the
kernel
. These libraries provide critical
APIs
including
ISO
C11
,
POSIX.1-2008
,
BSD
, OS-specific APIs and more. These APIs include such foundational facilities as
open
,
read
,
write
,
malloc
,
printf
,
getaddrinfo
,
dlopen
,
pthread_create
,
crypt
,
login
,
exit
and more.
History
[
edit
]
Version
|
Date
|
Highlights
|
0.1 ? 0.6
|
October 1991 ? February 1992
|
|
1.0
|
February 1992
|
|
1.01 ? 1.09.3
|
March 1992 ? December 1994
|
|
1.90 ? 1.102
|
May 1996 ? January 1997
|
|
2.0
|
January 1997
|
|
2.0.1
|
January 1997
|
|
2.0.2
|
February 1997
|
|
2.0.91
|
December 1997
|
|
2.0.95
|
July 1998
|
|
2.1
|
February 1999
|
|
2.1.1
|
March 1999
|
|
2.2
|
November 2000
|
|
2.2.1
|
January 2001
|
|
2.2.2
|
February 2001
|
|
2.2.3
|
March 2001
|
|
2.2.4
|
July 2001
|
|
2.3
|
October 2002
|
|
2.3.1
|
October 2002
|
|
2.3.2
|
February 2003
|
|
2.3.3
|
December 2003
|
|
2.3.4
|
December 2004
|
Minimum for
Linux Standard Base
(LSB) 3.0
|
2.3.5
|
April 2005
|
|
2.3.6
|
November 2005
|
|
2.4
|
March 2006
|
Minimum for
LSB
4.0, initial
inotify
support
|
2.5
|
September 2006
|
Full
inotify
support.
RHEL5 end of support
was November 30, 2020
; 3 years ago
(
2020-11-30
)
|
2.6
|
May 2007
|
|
2.7
|
October 2007
|
|
2.8
|
April 2008
|
|
2.9
|
November 2008
|
|
2.10
|
May 2009
|
Minimum for
LSB
5.0. Initial
psiginfo
Archived
19 September 2021 at the
Wayback Machine
support.
|
2.11
|
October 2009
|
SLES11 reached end of long-term support in
March 2022
.
|
2.12
|
May 2010
|
|
2.13
|
January 2011
|
|
2.14
|
June 2011
|
|
2.15
|
March 2012
|
|
2.16
|
June 2012
|
x32 ABI
support,
ISO C11
compliance,
SystemTap
|
2.17
|
December 2012
|
64-bit ARM
support
|
2.18
|
August 2013
|
Improved
C++11
support. Support for Intel
TSX
lock elision. Support for the Xilinx
MicroBlaze
and IBM
POWER8
microarchitectures.
|
2.19
|
February 2014
|
SystemTap probes for
malloc
. GNU Indirect Function (IFUNC) support for ppc32 and ppc64. New feature test macro _DEFAULT_SOURCE to replace _SVID_SOURCE and _BSD_SOURCE. Preliminary safety documentation for all functions in the manual. ABI change in ucontext and jmp_buf for s390/s390x.
|
2.20
|
September 2014
|
Support for file description locks
|
2.21
|
February 2015
|
New semaphore implementation
|
2.22
|
August 2015
|
Support to enable
Google Native Client
(NaCl), that originally ran on x86, running on
ARMv7-A
,
Unicode
7.0
|
2.23
|
February 2016
|
Unicode
8.0
|
2.24
|
August 2016
|
Some deprecated features have been removed
|
2.25
|
February 2017
|
The
getentropy
and
getrandom
functions, and the
<sys/random.h>
header file have been added.
|
2.26
|
August 2017
|
Improved performance (per-thread cache for malloc), Unicode 10 support
|
2.27
|
February 2018
|
Performance optimizations.
RISC-V
support.
|
2.28
|
August 2018
|
statx
,
renameat2
, Unicode 11.0.0
|
2.29
|
February 2019
|
getcpu
wrapper
- build and install all locales as directories with files
- optimized trigonomical functions
- Transactional Lock Elision for powercp64le ABI
- posix_spawn_file_actions_addchdir_np and posix_spawn_file_actions_addfchdir_np
- popen and system do not run atfork handlers anymore
- support for the C-SKY ABIV2 running on Linux
- strftime's default formatting of a locale's alternative year; the '_' and '-' flags can now be applied to its "%EY"
[7]
|
2.30
|
August 2019
|
Unicode 12.1.0, the dynamic linker accepts the
--preload
argument to preload shared objects, the
gettid
function has been added on Linux, Minguo (Republic of China) calendar support, new Japanese era added to ja_JP locale, memory allocation functions fail with total object size larger than
PTRDIFF_MAX
;
CVE
-
2019-7309
and CVE-
2019-9169
fixed
[8]
|
2.31
|
February 2020
|
Initial
C23
standard support
|
2.32
|
August 2020
|
Unicode 13.0, 'access' attribute for better warnings in GCC 10, i.e. to "help detect buffer overflows and other out-of-bounds accesses"
[9]
|
2.33
|
February 2021
|
HWCAPS
|
2.34
|
August 2021
|
libpthread, libdl, libutil, libanl has been integrated into libc.
|
2.35
|
February 2022
|
Unicode 14.0, C.UTF-8 locale, restartable sequences. Removed
Intel MPX
support.
|
2.36
|
August 2022
|
|
2.37
|
February 2023
|
|
2.38
|
August 2023
|
The strlcpy and strlcat functions added. libmvec support for ARM64.
|
2.39
|
January 2024
|
The stdbit.h header has been added from ISO C2X. Support for shadow stacks on x86_64, new security features, and the removal of libcrypt.
|
The glibc project was initially written mostly by Roland McGrath, working for the
Free Software Foundation
(FSF) in the summer of 1987 as a teenager.
[10]
[11]
In February 1988, FSF described glibc as having nearly completed the functionality required by
ANSI C
.
[12]
By 1992, it had the ANSI C-1989 and POSIX.1-1990 functions implemented and work was under way on POSIX.2.
[13]
In September 1995 Ulrich Drepper made his first contribution to the glibc and by 1997 most commits were made by him. Drepper held the maintainership position for many years and until 2012 accumulated 63% of all commits to the project.
[14]
In May 2009 glibc was migrated to a
Git
repository.
[14]
In 2010, a licensing issue was resolved which was caused by the
Sun RPC
implementation in glibc that was not GPL
compatible
. It was fixed by re-licensing the Sun RPC components under the
BSD license
.
[15]
[16]
In 2014, glibc suffered from an ABI breakage bug on s390.
[17]
In July 2017, 30 years after he started glibc, Roland McGrath announced his departure, "declaring myself maintainer emeritus and withdrawing from direct involvement in the project. These past several months, if not the last few years, have proven that you don't need me anymore".
[10]
In 2018, maintainer Raymond Nicholson removed a joke about
abortion
from the glibc source code. It was restored later by
Alexandre Oliva
after
Richard Stallman
demanded to have it returned.
[18]
In 2021, the
copyright
assignment requirement to the
Free Software Foundation
was removed from the project.
[19]
Fork and variant
[
edit
]
In 1994, the developers of the
Linux kernel
forked
glibc. Their fork, "Linux libc", was maintained separately until around 1998. Because the copyright attribution was insufficient, changes could not be merged back to the GNU Libc.
[20]
When the FSF released glibc 2.0 in January 1997, the kernel developers discontinued Linux libc due to glibc 2.0's superior compliance with POSIX standards.
[21]
glibc 2.0 also had better
internationalisation
and more in-depth translation,
IPv6
capability, 64-bit data access, facilities for multithreaded applications, future version compatibility, and the code was more portable.
[22]
The last-used version of Linux libc used the internal name (
soname
)
libc.so.5
. Following on from this, glibc 2.x on Linux uses the soname
libc.so.6
[23]
[
better source needed
]
In 2009,
Debian
and a number of
derivatives
switched from glibc to the variant
[25]
eglibc.
[26]
Eglibc was supported by a
consortium
consisting of
Freescale
,
MIPS
,
MontaVista
and
Wind River
.
[27]
It contained changes that made it more suitable for
embedded usage
and had added support for architectures that were not supported by glibc, such as the
PowerPC e500
. The code of eglibc was merged back into glibc at version 2.20.
[28]
Since 2014, eglibc is discontinued. The
Yocto Project
and Debian also moved back to glibc since the release of
Debian Jessie
.
[29]
Steering committee
[
edit
]
Starting in 2001 the library's development had been overseen by a committee,
[30]
with Ulrich Drepper
[31]
kept as the lead contributor and maintainer. The
steering committee
installation was surrounded by a public controversy, as it was openly described by Ulrich Drepper as a failed
hostile takeover
maneuver by
Richard Stallman
.
[32]
[33]
[34]
[35]
In March 2012, the steering committee voted to disband itself and remove Drepper in favor of a community-driven development process, with Ryan Arnold, Maxim Kuvyrkov, Joseph Myers, Carlos O'Donell, and
Alexandre Oliva
holding the responsibility of GNU maintainership (but no extra decision-making power).
[36]
[37]
[38]
Functionality
[
edit
]
glibc provides the functionality required by the
Single UNIX Specification
,
POSIX
(1c, 1d, and 1j) and some of the functionality required by
ISO
C11
,
ISO
C99
,
Berkeley Unix
(BSD) interfaces, the
System V Interface Definition
(SVID) and the
X/Open Portability Guide
(XPG), Issue 4.2, with all extensions common to XSI (
X/Open System Interface
) compliant systems along with all X/Open UNIX extensions.
In addition, glibc also provides extensions that have been deemed useful or necessary while developing
GNU
.
Supported hardware and kernels
[
edit
]
glibc is used in systems that run many different
kernels
and different
hardware
architectures. Its most common use is in systems using the
Linux kernel
on
x86
hardware, however, officially supported hardware
[39]
includes:
ARM
,
ARC
,
C-SKY
,
DEC Alpha
,
IA-64
,
Motorola m68k
,
MicroBlaze
,
MIPS
,
Nios II
,
PA-RISC
,
PowerPC
,
RISC-V
,
s390
,
SPARC
, and
x86
(old versions support
TILE
). It officially supports the
Hurd
and
Linux
kernels. Additionally, there are heavily patched versions that run on the kernels of
FreeBSD
and
NetBSD
(from which
Debian GNU/kFreeBSD
and
Debian GNU/NetBSD
systems are built, respectively), as well as a forked-version of
OpenSolaris
.
[40]
It is also used (in an edited form) and named
libroot.so
in
BeOS
and
Haiku
.
[41]
Use in small devices
[
edit
]
glibc has been criticized as being "
bloated
" and slower than other libraries in the past, e.g. by
Linus Torvalds
[42]
and
embedded Linux
programmers. For this reason, several
alternative C standard libraries
have been created which emphasize a smaller footprint. However, many small-device projects use GNU libc over the smaller alternatives because of its application support, standards compliance, and completeness. Examples include
Openmoko
[43]
and
Familiar Linux
for iPaq handhelds (when using the
GPE
display software).
[44]
Secure string functions
[
edit
]
glibc does not implement bounds-checking interfaces defined in
C11
and did not implement strlcpy and strlcat
[45]
[46]
until 2023 on the grounds that "in practice these functions can cause trouble, as their intended use encourages silent data truncation, adds complexity and inefficiency, and does not prevent all buffer overruns in the destinations."
[47]
The FAQ pointed out that the bounds-checking interfaces were optional in the ISO standard and that snprintf was available as an alternative.
[47]
Compatibility layers
[
edit
]
There are
compatibility layers
("
shims
") to allow programs written for other ecosystems to run on glibc interface offering systems. These include
libhybris
, a compatibility layer for
Android's
Bionic
, and
Wine
, which can be seen as a compatibility layer from
Windows
APIs to glibc and other native APIs available on Unix-like systems.
See also
[
edit
]
Notes
[
edit
]
- ^
LGPL-2.1-or-later since 2001-07-06, version 2.2.4.
[3]
[4]
- ^
LGPL-2.0-or-later from 1992 to 2001-07-05. Version 1.04? to 2.2.3.
[5]
[6]
References
[
edit
]
- ^
Corbet, Jonathan (28 March 2012).
"A turning point for GNU libc"
. LWN.net.
Archived
from the original on 23 April 2016
. Retrieved
5 April
2012
.
- ^
Andreas K. Huttel (31 January 2024).
"The GNU C Library version 2.39 is now available"
. Retrieved
1 February
2024
.
- ^
a
b
"sourceware.org Git ? glibc.git/blob ? Makefile"
.
sourceware.org
.
Archived
from the original on 10 June 2021
. Retrieved
10 June
2021
.
LGPL-2.1-or-later in the headers
- ^
"sourceware.org Git ? glibc.git/commit ? Update to LGPL v.2.1"
.
sourceware.org
. 6 July 2001.
Archived
from the original on 10 June 2021
. Retrieved
10 June
2021
.
LGPL-2.1-or-later in the headers
- ^
"glibc-1.04.tar.Z"
. 4 September 1992.
Archived
from the original on 22 December 2021
. Retrieved
22 December
2021
.
- ^
"sourceware.org Git ? glibc.git/commit ? Initial import: Makefile"
.
sourceware.org
. 18 February 1995.
Archived
from the original on 10 June 2021
. Retrieved
10 June
2021
.
LGPL-2.0-or-later in the headers
- ^
"sourceware.org Git ? glibc.git/blob ? NEWS"
.
Archived
from the original on 21 March 2022
. Retrieved
26 April
2019
.
- ^
"sourceware.org Git ? glibc.git/blob ? NEWS"
.
Archived
from the original on 26 September 2019
. Retrieved
26 April
2019
.
- ^
"The GNU C Library version 2.32 is now available"
.
sourceware.org
.
Archived
from the original on 28 September 2020
. Retrieved
13 August
2020
.
- ^
a
b
"Roland McGrath bows out as glibc maintainer [LWN.net]"
.
lwn.net
. 7 July 2017.
Archived
from the original on 1 August 2020
. Retrieved
8 July
2017
.
- ^
Chirgwin, Richard (10 July 2017).
"Roland McGrath steps down as glibc maintainer after 30 years"
.
The Register
. Situation Publishing.
Archived
from the original on 7 March 2024
. Retrieved
1 June
2024
.
- ^
"GNU's Bulletin, vol. 1 no. 4, February, 1988"
.
Archived
from the original on 16 April 2016
. Retrieved
16 April
2014
.
Most libraries are done. Roland McGrath [...] has a nearly complete set of ANSI C library functions. We hope they will be ready some time this spring.
- ^
"GNU's Bulletin, vol. 1 no. 12"
.
Archived
from the original on 11 March 2016
. Retrieved
16 April
2014
.
It now contains all of the ANSI C-1989 and POSIX.1-1990 functions, and work is in progress on POSIX.2 and Unix functions (BSD and System V)
- ^
a
b
Corbet, Jonathan (28 March 2012).
"A turning point for GNU libc"
. LWN.net.
Archived
from the original on 23 April 2016
. Retrieved
5 April
2012
.
Of the nearly 19,000 commits found in the project's git repository (which contains changes back to 1995), over 12,000 were made by Ulrich.
- ^
"Glibc finally free software ? The H Open: News and Features"
.
H-online
.
Archived
from the original on 21 March 2022
. Retrieved
19 September
2021
.
- ^
Phipps, Simon (2 September 2010).
"Gnu/Linux: Finally, it's really free software"
.
InfoWorld
.
Archived
from the original on 28 October 2021
. Retrieved
19 September
2021
.
- ^
Corbet, Jonathan.
"The glibc s390 ABI break [LWN.net]"
.
LWN.net
.
Archived
from the original on 17 March 2022
. Retrieved
17 March
2022
.
- ^
Claburn, Thomas.
"Glibc 'abortion joke' diff tiff leaves Richard Stallman miffed"
.
The Register
.
Archived
from the original on 17 January 2023
. Retrieved
17 January
2023
.
- ^
Halfacree, Gareth.
"Open-source projects glibc and gnulib look to sever copyright ties with Free Software Foundation"
.
The Register
.
Archived
from the original on 17 January 2023
. Retrieved
17 January
2023
.
- ^
"History of glibc and Linux libc"
.
Free Software Magazine
.
Archived
from the original on 26 September 2021
. Retrieved
10 May
2021
.
- ^
"Forking: it could even happen to you"
. 24 October 2000. Archived from
the original
on 15 September 2009.
the split between GNU LIBC and the Linux LIBC -- it went on for years while Linux stabilized, and then the forks re-merged into one project
- ^
Lee, Elliot (9 July 1998).
"A Technical Comparison of glibc 2.x With Legacy System Libraries"
. Archived from
the original
on 11 April 2004.
- ^
Moen, Rick (20 May 2021) [14 Nov 1999].
"Fear of Forking essay"
.
linuxmafia.com
. 6. glibc --> Linux libc --> glibc.
Archived
from the original on 27 November 2023.
- ^
"EGLIBC: FAQ"
.
eglibc.org
. Archived from
the original
on 17 March 2012
. Retrieved
16 September
2021
.
- ^
The eglibc developers emphasized themselves that eglibc is not a fork of glibc, but a variant, accepting patches from the upstream glibc project.
[24]
- ^
Vaduva, Alexandru (2016).
Linux : embedded development: leverage the power of Linux to develop captivating and powerful embedded Linux projects : a course in three modules
. Alex Gonzalez, Chris Simmonds. Birmingham, UK: Packt Publishing. p. 24.
ISBN
978-1-78712-445-5
.
OCLC
960471438
.
- ^
Stiebert, Julius (6 May 2009).
"Debian wechselt zur Eglibc"
.
golem.de
.
Archived
from the original on 16 September 2021
. Retrieved
16 September
2021
.
- ^
Simmonds, Chris (2017).
Mastering embedded Linux programming: unleash the full potential of embedded Linux
(2nd ed.). Birmingham, UK. p. 26.
ISBN
978-1-78728-885-0
.
OCLC
995052708
.
{{
cite book
}}
: CS1 maint: location missing publisher (
link
)
- ^
Vaduva, Alexandru (2015).
Learning embedded Linux using the Yocto project: develop powerful embedded Linux systems with the Yocto project components
. Birmingham, UK. p. 29.
ISBN
978-1-78439-519-3
.
OCLC
914797028
.
{{
cite book
}}
: CS1 maint: location missing publisher (
link
)
- ^
"glibc homepage"
.
Archived
from the original on 22 April 2016
. Retrieved
16 April
2014
.
In 2001 The GNU C Library Steering Committee ..., was formed and currently consists of Mark Brown, Paul Eggert, Andreas Jaeger, Jakub Jelinek, Roland McGrath and Andreas Schwab.
- ^
"Ulrich Drepper"
. LinkedIn.
Archived
from the original on 10 September 2014
. Retrieved
13 June
2012
.
- ^
online, heise (19 August 2001).
"Open-Source-Entwickler kritisiert Stallman"
.
heise online
(in German).
Archived
from the original on 16 September 2021
. Retrieved
16 September
2021
.
- ^
Drepper, Ulrich (26 June 2000).
"RMS is at it again"
. sourceware.org.
Archived
from the original on 28 December 2012
. Retrieved
20 November
2015
.
A few weeks ago RMS started the next attack on me (a single mail, followed by indirect tries to take influence, followed by another mail today). The essence is that he complains I am not following "GNU policies" and therefore have to be replaced by a steering committee of which I could be a part. Some of you (namely Roland and Andreas S.) probably know about this since he proposed both as other members of the committee. In addition there was Mark Brown listed (I know somebody of this name at IBM who would also fit in this group but I'm not sure whether it is really him.) Anyhow, I completely reject this. It is not helping at all, the opposite is true. First, I am not aware of any essential policies I'm violating. The only ones are that I'm not following orders from RMS which clearly have political intends (which is of course a sacrilege) and possibly that I do not care about Winblowz (if the latter counts at all). None of this will change in any way.
- ^
Drepper, Ulrich (15 August 2001).
"glibc 2.2.4"
. sourceware.com.
Archived
from the original on 9 April 2016
. Retrieved
29 November
2015
.
And now for some not so nice things. Stallman recently tried what I would call a hostile takeover of the glibc development. He tried to conspire behind my back and persuade the other main developers to take control so that in the end he is in control and can dictate whatever pleases him. This attempt failed but he kept on pressuring people everywhere and it got really ugly. In the end I agreed to the creation of a so-called "steering committee" (SC).
- ^
rms-accused-of-attempting-glibc-hostile-takeover
Archived
1 August 2020 at the
Wayback Machine
on
slashdot
.com on 19 August 2001
- ^
"The GNU C Library Steering Committee disbands ? The H Open: News and Features"
.
H-Online
.
Archived
from the original on 21 March 2023
. Retrieved
16 March
2023
.
- ^
McGrath, Roland (26 March 2012).
"glibc steering committee dissolving"
. Sourceware.org.
Archived
from the original on 26 September 2019
. Retrieved
13 June
2012
.
- ^
Myers, Joseph S. (26 March 2012).
"GNU C Library development and maintainers"
. Sourceware.org.
Archived
from the original on 26 September 2019
. Retrieved
13 June
2012
.
- ^
"The GNU C Library machine maintainers"
.
Archived
from the original on 18 April 2016
. Retrieved
8 October
2015
.
- ^
Bartley, David; Spang, Michael.
"GNU/kOpenSolaris (GNU libc/base + OpenSolaris kernel)"
. Archived from
the original
on 6 November 2019
. Retrieved
16 December
2008
.
- ^
"Haiku Source"
.
GitHub
.
Archived
from the original on 1 May 2016
. Retrieved
15 October
2014
.
libroot.so is not part of GNU project and is included in Haiku source code.
- ^
Torvalds, Linus (9 January 2002).
"Posting to the glibc mailing list"
.
Archived
from the original on 12 October 2015
. Retrieved
22 July
2007
.
- ^
"OpenMoko components"
.
Archived
from the original on 22 April 2016
. Retrieved
13 May
2008
.
We will use glibc (not uClibC) ... The alternatives may save more space and be more optimized, but are more likely to give us integration headaches
- ^
"Re: [Familiar] Which glibc for Familiar 0.8.4 ?"
.
Archived
from the original on 12 March 2022
. Retrieved
26 November
2018
.
Question: which version of the GLIBC was used to build the Familiar 0.8.4 ? Answer: 2.3.3
- ^
Kerrisk, Michael.
"The ups and downs of strlcpy()"
.
LWN.net
.
Archived
from the original on 9 December 2023
. Retrieved
9 December
2023
.
- ^
Corbet, Jonathan.
"Adding strlcpy() to glibc"
.
LWN.net
.
Archived
from the original on 9 December 2023
. Retrieved
9 December
2023
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"FAQ"
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