Glibc

"glibc" redirects here. Not to be confused with glib or gnulib.

GNU C Library

Original author(s)	Roland McGrath
Developer(s)	GNU Project
Initial release	1987 (1987)
Repository	sourceware.org/git/glibc.git
Operating system	Unix-like
Type	Runtime library
License	GNU Lesser General Public License
Website	www.gnu.org/software/libc/

The GNU C Library, commonly known as glibc, is the GNU Project's implementation of the C standard library. Originally written by the Free Software Foundation (FSF) for the GNU operating system, the library's development had been overseen by a committee since 2001, with Ulrich Drepper as the lead contributor and maintainer. In March 2012, the steering committee voted to disband itself, in favor of a community-driven development process, with Ryan Arnold, Maxim Kuvyrkov, Joseph Myers, Carlos O'Donell, and Alexandre Oliva as non-decision making project stewards.

Released under the GNU Lesser General Public License, glibc is free software.

History

glibc was initially written mostly by Roland McGrath, working for the Free Software Foundation (FSF) in the 1980s.

In February 1988, FSF described glibc as having nearly completed the functionality required by ANSI C. By 1992, it had the ANSI C-1989 and POSIX.1-1990 functions implemented and work was under way on POSIX.2.

A temporary fork

In the early 1990s, the developers of the Linux kernel forked glibc. Their fork, called "Linux libc", was maintained separately for years and released versions 2 through 5.

When FSF released glibc 2.0 in January 1997, it had much more complete POSIX standards compliance, better internationalisation and multilingual function, IPv6 capability, 64-bit data access, facilities for multithreaded applications, future version compatibility, and the code was more portable. At this point, the Linux kernel developers discontinued their fork and returned to using FSF's glibc.

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 (Alpha and IA64 architectures now use libc.so.6.1, instead). The soname is often abbreviated as libc6 (for example in the package name in Debian) following the normal conventions for libraries.

According to Richard Stallman, the changes that had been made in Linux libc could not be merged back into glibc because the authorship status of that code was unclear and the GNU project is quite strict about recording copyright and authors.

Version history

Version	Date	Notes
0.1 – 0.6	Oct 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	Debian 3.1 (Sarge)
2.3.3	December 2003
2.3.4	December 2004	Standard for LSB 3.0, Used in RHEL 4 (Update 5)
2.3.5	April 2005	Used in SLES 9
2.3.6	November 2005	Debian 4.0 (Etch)
2.4	March 2006	Standard for LSB 4.0, Used in SLES 10
2.5	September 2006	Used in RHEL 5
2.6	May 2007
2.7	October 2007	Debian 5 (Lenny), Ubuntu 8.04
2.8	April 2008
2.9	November 2008
2.10	May 2009
2.11	October 2009	SLES 11, Ubuntu 10.04, eglibc used in Debian 6 (Squeeze)
2.12	May 2010	Used in RHEL 6
2.13	January 2011	eglibc 2.13 used in Debian 7 (Wheezy)
2.14	June 2011
2.15	March 2012	Used in Ubuntu 12.04 and 12.10
2.16	June 2012	x32 ABI support, ISO C11 compliance, SystemTap
2.17	December 2012	64-bit ARM support; used in Ubuntu 13.04

Supported hardware and kernels

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 includes: x86, Motorola 680x0, DEC Alpha, PowerPC, ETRAX CRIS, s390, and SPARC. 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 the kernel of OpenSolaris. It is also used (in an edited form) and named libroot.so in BeOS and Haiku.

Functionality

glibc provides the functionality required by the Single UNIX Specification, POSIX (1c, 1d, and 1j) and some of the functionality required by 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.

Use in small devices

glibc has been criticized as being "bloated" and slower than other libraries in the past, e.g. by Linus Torvalds and embedded Linux programmers. For this reason, several alternative C standard libraries have been created which emphasize a smaller footprint. Among them are Bionic (based mostly on libc from BSD and used in Android), dietlibc, uClibc, Newlib, Klibc, and EGLIBC (used in Debian, Ubuntu and Ark Linux).

However, many small-device projects use GNU libc over the smaller alternatives because of its application support, standards compliance, and completeness. Examples include Openmoko and Familiar Linux for iPaq handhelds (when using the GPE display software).

See also

• Gnulib
• EGLIBC
• uClibc
• dietlibc

External links

• GNU libc homepage
• GNU libc developers' page