GNU C Library
From Wikipedia, the free encyclopedia
The GNU C Library, commonly known as glibc, is the C standard library released by the GNU Project. Originally written by the Free Software Foundation (FSF) for the GNU operating system, the library's development has been overseen by a committee since 2001, with Ulrich Drepper as the lead contributor and maintainer.
Released under the GNU Lesser General Public License, glibc is free software.
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[edit] History
glibc was initially written mostly by Roland McGrath, working for the FSF in the 1980s.
In February 1988, FSF described glibc as having nearly completed the functionality required by ANSI C.[1] By 1992, it had the ANSI C-1989 and POSIX.1-1990 functions implemented and work was under way on POSIX.2.[2]
[edit] 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 1996, it had much more complete POSIX standards support, better internationalisation/multilingual support, support for IPv6, 64-bit data access, support for multithreaded applications, future version compatibility support, and more portable source.[3] At this point, the Linux kernel developers discontinued their fork and returned to using FSF's glibc.[4]
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[5] (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.[6]
[edit] Supported hardware and kernels
Glibc is used in systems which run many different kernels and different hardware architectures. Its most common use is in systems using the Linux kernel on x86 hardware, but officially supported hardware includes: x86, Motorola 680x0, DEC Alpha, PowerPC, ARM, ETRAX CRIS, s390, and SPARC. It officially supports the Hurd and Linux kernels, although 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). It is also used (in an edited form) as the libroot of BeOS and hence Haiku.
[edit] 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 Description (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 which have been deemed useful or necessary while developing GNU.
[edit] Criticism
Glibc has been criticized as being "bloated" and slower than other libraries in the past, e.g. by Linus Torvalds and embedded Linux programmers.[7] For this reason, several alternative C standard libraries have been created which emphasize a smaller footprint, among them dietlibc, uClibc and Newlib.
[edit] See also
[edit] References
- ^ http://www.gnu.org/bulletins/bull4.html. “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. “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)”
- ^ Elliot Lee (2001). A Technical Comparison of glibc 2.x With Legacy System Libraries.
- ^ Forking: it could even happen to you. “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”
- ^ Fear of Forking essay, see "6. glibc --> Linux libc --> glibc".
- ^ Fear of Forking, footnote on Stallman's merge comments.
- ^ Linus Torvalds: Posting to the glibc mailing list, 9 January 2002 19:02:37
[edit] External links
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| Libraries | C standard library · glibc · Dietlibc · uClibc · Newlib |
| History | Criticism of the C programming language |
| Language Features | String · Syntax · Preprocessor · Variable types and declarations · Functions |
| Descendants | C++ · Objective-C · D |
| C and Other Languages | Compatibility of C and C++ · Operators in C and C++ · Comparison of Pascal and C · C to Java byte-code compiler |
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| History | GNU Manifesto · GNU Project · Free Software Foundation · History of free software |  |
| GNU licences | GNU General Public License · GNU Lesser General Public License · Affero General Public License · GNU Free Documentation License · GPL linking exception | |
| Software | GNU · Hurd · (GNU variants) · GNOME · Gnuzilla · IceCat · Gnash · Bash · GCC · GNU Emacs · glibc · Coreutils · GNU build system · Other GNU packages and programs | |
| Speakers | Robert J. Chassell · Loïc Dachary · Ricardo Galli · Georg C. F. Greve · Federico Heinz · Benjamin Mako Hill · Bradley M. Kuhn · Eben Moglen · Brett Smith · Richard Stallman · John Sullivan · Leonard H. Tower Jr. | |
