µ C l i b c

uClibc -- a C library for embedded systems

uClibc (aka µClibc/pronounced yew-see-lib-see) is a C library for developing embedded Linux systems. It is much smaller than the GNU C Library, but nearly all applications supported by glibc also work perfectly with uClibc. Porting applications from glibc to uClibc typically involves just recompiling the source code. uClibc even supports shared libraries and threading. It currently runs on standard Linux and MMU-less (also known as µClinux) systems with support for alpha, ARM, i386, i960, h8300, m68k, mips/mipsel, PowerPC, SH, SPARC, and v850 processors.

If you are building an embedded Linux system and you find that glibc is eating up too much space, you should consider using uClibc. If you are building a huge fileserver with 12 Terabytes of storage, than using glibc may be a better choice...

uClibc is maintained by Erik Andersen and is licensed under the GNU LIBRARY GENERAL PUBLIC LICENSE . This license allows you to make closed source commercial applications using uClibc (Please consider sharing some of the money you make ;-). You do not need to give away all your source code just because you use uClibc and/or run on Linux.

### Mailing List Information

uClibc has a mailing list.
To subscribe, go and visit this page.

### Frequently Asked Questions

Before asking questions on the uClibc mailing list, you might want to take a look at the list of Frequently Asked Questions or you might want to search the mailing list archives... ...

### Working Applications List

These days, pretty much everything compiles with uClibc. This is a list of applications that are known to work just fine with uClibc. Since most applications work just fine with uClibc, we are especially interested in knowing about any applications that either do not compile or do not work properly with uClibc. Submissions are welcome!

Latest News

- 25 January 2003, uClibc 0.9.17 Released
  CodePoet Consulting is pleased to announce the immediate availability of uClibc 0.9.17. The biggest piece of news with this release, thanks to Manuel Novoa's continuing hard work, is that we now have fully standards compliant locale support (optional of course). The support works nicely, (though configuring the locales you wish to support is still manual -- a task for the next release). Full locale data for over 300 locales adds approximately 250k. The collation data for all supported locales is roughly 180k. This may seem rather large to some -- but it is much smaller than the approximately 40 MB needed by Glibc to provide the same data. And if you don't need it, you can either disable locale support entirely, or enable a smaller set of locales.

  This release also fixes lots and lots of bugs. The arm architecture support (I am embarrassed to note) was totally broken in the last release, but is now working as expected. A security problem (a buffer overflow in getlogin_r) was fixed. And there were architecture updates across the board (x86, arm, powerpc, cris, h8300, sparc, and mips). And of course, this release includes the usual pile of bug fixes. Many thanks for the large number of patches and fixes that were contributed!

  Unfortunately, this release is not binary compatible with earlier uClibc releases. As noted as item 3 in Glibc_vs_uClibc_Differences.txt, uClibc does not (yet) attempt to ensure binary compatibility across releases. We will eventually do that (once we reach the "1.0" release) but not yet. A few bugs turned up that needed to be fixed, and the only good way to fix them was to change some fundamental data structure sizes. As a result, this release is _NOT_ binary compatible with earlier releases -- you will need to recompile your applications. The x86, arm, powerpc, and mips architectures (i.e. the systems Erik has available in his office for testing) have been tested and are known to work following this change. Other architectures may need additional updates. Sorry about that, but it had to be done.

  As usual, the Changelog and source code for this release are available here. You might want to download uClibc from the closest kernel.org mirror site. Just pick the closest mirror site, and then go to http://www.XX.kernel.org/pub/linux/libs/uclibc/ to download uClibc, where XX is your two letter country code.

- 25 January 2003, dev system updates, arm image released
  A number of additional problems have been fixed and the arm build is now, finally, compiling and working as expected. As such, I have updated the i386 development system image, the powerpc development system image, and I am also releasing upon an unsuspecting world the brand new arm development system image! Have fun!

  All three development system images were compiled and built using the stock buildroot system. These were also built using the (about to be announced in a couple on minutes) uClibc 0.9.17 release, so if you want to begin compiling and testing stuff with uClibc, but you don't feel like spending the _hours_ it takes to download, configure, and build your own uClibc based development system -- then you may want to download these and give them a try. They each contain a 100 MB ext2 filesystem with everything you need to begin compiling your own applications. I have (at least minimally) tested each of them and verified that the included gcc and g++ compilers produce working uClibc linked executables.

  Oh, and I have also have updated the uClibc/gcc toolchain builders, so if you just want a simple uClibc/gcc toolchain, one of these should work for you.

- 10 January 2003, dev system updates, powerpc image released
  A few problems showed up in yesterday's development system release (adduser was broken, gdb didn't work, libstdc++ shared libs were missing, etc). So I've updated the i386 development system image to fix these problems. Also, the powerpc development system image has finally finished compiling and is now released upon an unsuspecting world. Have fun!

- 9 January 2003, uClibc development system released
  CodePoet Consulting (i.e. Erik) has been working hard on buildroot recently, and is pleased to offer a full stand-alone uClibc-only development system. This is an ext2 filesystem for i386 containing all the development software you need to build your own uClibc applications. With bash, awk, make, gcc, g++, autoconf, automake, ncurses, zlib, openssl, openssh, gdb, strace, valgrind, busybox, GNU coreutils, and more, this should have pretty much everything you need to get started building your own applications linked against uClibc. By using a uClibc only system, you can avoid all the painful cross-configuration problems that have made using uClibc somewhat painful in the past. A powerpc and an arm version are in progress. Expect them to be released shortly....

  The uClibc development system is an 18MB bzip2 compressed ext2 filesystem, so be prepared to wait if you are on a slow link. If you wish to have more space, you can loop mount it and 'cp -a' the contents to their own partition, or do what I did... WARNING, the following can be very dangerous. Please be sure you know what you are doing before trying this. I am not responsible if you lose all your important data.I had a spare hard drive (in my case /dev/hdg but you'll want to adapt this to your own needs), so I partitioned it with a single ext2 partition filling the drive (in my case /dev/hdg1). Then I ran:

          bzcat root_fs_0.9.17-i386.bz2 | dd of=/dev/hdg1
          e2fsck -f /dev/hdg1
          resize2fs -p /dev/hdg1

  which overwrote everything on /dev/hdg with the new uClibc devel system, and then expanded the filesystem with the uClibc devel system till it filled the whole drive.

- Old News
  Click here to read older news.

Sponsors

Please visit our sponsors and thank them for their support! They have provided money, equipment, bandwidth, etc. Next time you need help with a project, consider these fine companies! Several individuals have also contributed (If you have contributed and would like your name added here, just email Erik and let him know).

- opensource.se
  Embedded open source consulting in Europe.
- http://i-netinnovations.com/
  Web hosting (currently hosting busybox.net and uclibc.org)
- Codepoet Consulting
  Custom Linux, embedded Linux, BusyBox, and uClibc development.

Do you like uClibc? Do you need support? Do you need some feature added? Then why not help out? We are happy to accept donations (such as bandwidth, mirrors sites, and hardware for the various architectures). We can also provide support contracts, and implement funded feature requests. To contribute, you can either click on the Donate image to donate using PayPal, or you can contact Erik at CodePoet Consulting (we have a credit card machine so you can avoid PayPal if you wish).

Download

- Source for the latest release can always be downloaded from http://www.uclibc.org/downloads
- A daily snapshot of the source is available for those wishing to follow uClibc developments, but cannot or do not wish to use CVS.
- uClibc has a publically browsable CVS tree.
- Anonymous CVS access is available to let you track development.
- CVS write access is also available for those that are actively contributing.

Other Open Source C libraries:

I am currently aware of the following open source C libraries.

- GNU C Library (aka glibc)
- Al's FREE C Runtime Library
- diet libc
- the minix C library
- newlib
- and there is a C library, for eCos as well.

Links to other useful stuff

- The uClibc home page

- The uClibc CVS tree

- BusyBox

- udhcp

- The uClinux home page

- The uClinux CVS repository

- CodePoet Consulting

Mail all comments, insults, suggestions and bribes to Erik Andersen |  |  |  |  |