From 557eef285f38cdc5a3d7a4c8b7d0d5182193ea2e Mon Sep 17 00:00:00 2001 From: Mike Frysinger Date: Tue, 17 Apr 2007 13:11:21 +0000 Subject: move uclibc.org out of actual source tree --- docs/uclibc.org/FAQ.html | 693 ----------------------------------------------- 1 file changed, 693 deletions(-) delete mode 100644 docs/uclibc.org/FAQ.html (limited to 'docs/uclibc.org/FAQ.html') diff --git a/docs/uclibc.org/FAQ.html b/docs/uclibc.org/FAQ.html deleted file mode 100644 index a21e2bdcb..000000000 --- a/docs/uclibc.org/FAQ.html +++ /dev/null @@ -1,693 +0,0 @@ - - - -

Frequently Asked Questions

- -This is a collection of some of the most frequently asked questions -about uClibc. Some of the questions even have answers. If you -have additions to this FAQ document, we would love to add them, - -
    -
  1. Why is it called uClibc? -
  2. What platforms does uClibc run on? -
  3. Why are you doing this? What's wrong with glibc? -
  4. So uClibc is smaller then glibc? Doesn't that mean it - completely sucks? How could it be smaller and not suck? -
  5. Why should I use uClibc? -
  6. If I use uClibc, do I have to release all my source code to the world for - free? I want to create a closed source commercial application and I want - to protect my intellectual property. -
  7. Can I use it on my x86 development system? -
  8. Does uClibc support shared libraries? -
  9. How do I compile programs with uClibc? -
  10. Do I really need to build a uClibc toolchain? -
  11. What happened to the old toolchain wrapper? -
  12. Is a pre-compiled uClibc development system available? -
  13. I think I found a bug in uClibc! What should I do?! -
  14. My package builds fine but link fails with errors like "undefined reference - to __fputc_unlocked", who do I blame?! -
  15. My package builds fine but link fails with errors like "undefined reference - to rpl_realloc / rpl_malloc", who do I blame?! -
  16. Why do I keep getting "sh: can't access tty; job control - turned off" errors? Why doesn't Control-C work within my shell? -
  17. How do I make autoconf and automake behave? -
  18. When I run 'ldd' to get a list of the library dependencies - for a uClibc binary, ldd segfaults! What should I do? -
  19. Why does localtime() return times in UTC even when I have my timezone set? -
  20. What is the history of uClibc? Where did it come from? -
  21. I demand that you to add <favorite feature> right now! How come - you don't answer all my questions on the mailing list instantly? I demand - that you help me with all of my problems Right Now! -
  22. I need help with uClibc! What should I do? -
  23. I need you to add <favorite feature>! Are the uClibc developers willing to - be paid in order to fix bugs or add in <favorite feature>? Are you willing to provide - support contracts? -
  24. I think you guys are great and I want to help support your work! - - -
- - -
-

-

Why is it called uClibc?

-

- - The letter 'u' is short for µ (the greek letter "mu"). µ is commonly used - as the abbreviation for the word "micro". The capital "C" is short for - "controller". So the name uClibc is sortof an abbreviation for "the - microcontroller C library". For simplicity, uClibc is pronounced - "yew-see-lib-see". -

- The name is partly historical, since uClibc was originally - created to support µClinux, a port of - Linux for MMU-less microcontrollers such as the Dragonball, Coldfire, and - ARM7TDMI. These days, uClibc also works just fine on normal Linux systems - (such as i386, ARM, and PowerPC), but we couldn't think of a better name. - -

-

-

What platforms does uClibc run on?

-

- - - Currently uClibc runs on alpha, ARM, cris, i386, i960, h8300, - m68k, mips/mipsel, PowerPC, SH, SPARC, and v850 processors. - - -

-

-

Why are you doing this? What's wrong with glibc?

-

- - Initially, the project began since the GNU C library lacked support for - MMU-less systems, and because glibc is very large. The GNU C library is - designed with a very different set of goals then uClibc. The GNU C library - is a great piece of software, make no mistake. It is compliant with just - about every standard ever created, and runs on just about every operating - system and architecture -- no small task! But there is a price to be paid - for that. It is quite a large library, and keeps getting larger with each - release. It does not even pretend to target embedded systems. To quote - from Ulrich Drepper, the maintainer of GNU libc: "...glibc is not the right - thing for [an embedded OS]. It is designed as a native library (as opposed - to embedded). Many functions (e.g., printf) contain functionality which is - not wanted in embedded systems." 24 May 1999 - - - -

-

-

So uClibc is smaller then glibc? Doesn't that mean it completely sucks? -How could it be smaller and not suck?

-

-

- - uClibc and glibc have different goals. glibc strives for features - and performance, and is targeted for desktops and servers with - (these days) lots of resources. It also strives for ABI stability. - -

- - On the other hand, the goal of uClibc is to provide as much functionality - as possible in a small amount of space, and it is intended primarily for - embedded use. It is also highly configurable in supported features, at the - cost of ABI differences for different configurations. uClibc has been - designed from the ground up to be a C library for embedded Linux. We don't - need to worry about things like MS-DOS support, or BeOS, or AmigaOs any - other system. This lets us cut out a lot of complexity and very carefully - optimize for Linux. - -

- - In other cases, uClibc leaves certain features (such as full C99 Math - library support, wordexp, IPV6, and RPC support) disabled by default. - Those features can be enabled for people that need them, but are otherwise - disabled to save space. - -

- - Some of the space savings in uClibc is obtained at the cost of performance, - and some is due to sacrificing features. Much of it comes from aggressive - refactoring of code to eliminate redundancy. In regards to locale data, - elimination of redundant data storage resulted in substantial space - savings. The result is a libc that currently includes the features needed - by nearly all applications and yet is considerably smaller than glibc. To - compare "apples to apples", if you take uClibc and compile in locale data - for about 170 UTF-8 locales, then uClibc will take up about 570k. If you - take glibc and add in locale data for the same 170 UTF-8 locales, you will - need over 30MB!!! - -

- - The end result is a C library that will compile just about everything you - throw at it, that looks like glibc to application programs when you - compile, and is many times smaller. - - -

-

-

Why should I use uClibc?

-

- - I don't know if you should use uClibc or not. It depends on your needs. - If you are building an embedded Linux system and you are tight on space, then - using uClibc instead if glibc may be a very good idea. - -

- - 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, then using glibc may make more sense. Unless, for - example, that 12 Terabytes will be Network Attached Storage and - you plan to burn Linux into the system's firmware... - - - -

-

-

If I use uClibc, do I have to release all my source code to the world for - free? I want to create a closed source commercial application and I want - to protect my intellectual property.

-

- - No, you do not need to give away your application source code just because - you use uClibc and/or run on Linux. uClibc is licensed under the Lesser GPL license, just - like the GNU C library (glibc). Please read this license, or have a lawyer - read this license if you have any questions. Here is my brief summary... - Using shared libraries makes complying with the license easy. You can - distribute a closed source application which is linked with an unmodified - uClibc shared library. In this case, you do not need to give away any - source code for your application. Please consider sharing some of the - money you make with us! :-) -

- - If you make any changes to uClibc, and distribute uClibc or distribute any - applications using your modified version, you must also distribute the - source code for uClibc containing all of your changes. -

- - If you distribute an application which has uClibc statically linked, you - must also make your application available as an object file which can later - be re-linked against updated versions of uClibc. This will (in theory) - allow your customers to apply uClibc bug fixes to your application. You do - not need to make the application object file available to everyone, just to - those you gave the fully linked application. - - -

-

-

Can I use it on my x86 development system?

-

- - Sure! In fact, this can be very nice during development. By - installing uClibc on your development system, you can be sure that - the code you are working on will actually run when you deploy it on - your target system. - - - -

-

-

Does uClibc support shared libraries?

-

- - Yes. uClibc has native shared library support on i386, ARM, mips, - SH, CRIS, and PowerPC processors. Other architectures can use shared - libraries but will need to use the GNU libc shared library loader. -

- Shared Libraries are not currently supported by uClibc on MMU-less systems. - SnapGear has implemented - shared library support for MMU-less systems, however, so if you need MMU-less - shared library support they may be able to help. - - -

-

-

How do I compile programs with uClibc?

-

- - You will need to have your own uClibc toolchain. A toolchain consists - of GNU binutils, - the gcc compiler, and uClibc, all - built to produce binaries for your target system linked with uClibc. - You can build your own native uClibc toolchain using the - uClibc buildroot system. - -

- To build your own uClibc toolchain, follow the following simple - steps: -

- -
-

-

Do I really need to build a uClibc toolchain?

-

- - Yes, you really do need to build a toolchain to produce uClibc binaries. - We used to provide a toolchain wrapper, but that has been removed due to - numerous problems. The uClibc developers have gone to a lot of trouble - to produce the - uClibc buildroot system, - which makes it easy to build your own uClibc toolchain and/or an initial - uClibc based system. - -

- Feel free to take the gcc and binutils patches we provide and use them in - your own toolchain build system. If you choose to use your own toolchain - build system, you will need to use these patches since the upstream GNU - binutils and gcc releases do not currently have full support for building a - uClibc toolchain. - - -

-

-

What happened to the old toolchain wrapper?

-

- - It is possible in some limited cases to re-use an existing glibc toolchain - and subvert it into building uClibc binaries by using gcc commands such as - "-nostdlib" and "-nostdinc". In fact, this used to be the recommended - method for compiling programs with uClibc, and we made this easy to do by - providing a uClibc toolchain wrapper, which attempted to automagically subvert - an existing glibc toolchain. - -

- - This toolchain wrapper was removed from uClibc 0.9.22, and it will not be - coming back. This is because it proved impossible to completely subvert an - existing toolchain in many cases, and therefore proved to be a real - maintainence burder. As uClibc became more capable, the many problems with - re-using an existing glibc toolchain led us to conclude that the only safe - and sane way to build uClibc binaries was to use a uClibc toolchain. - -

- - Some discussion on the reasoning behind this decision can be found here: - - http://www.uclibc.org/lists/uclibc/2003-October/007315.html - in the uClibc mailing list archives. - -

-

-

Is a pre-compiled uClibc development system available?

-

- - If you want to be really lazy and start using uClibc right away - without needing to compile your own toolchain or anything, you can grab a - pre-compiled uClibc development system. These are currently available for - - arm, - armeb, - i386, - mips, - mipsel, - powerpc, and - sh4. - -

- - These are bzip2 compressed ext2 filesystems containing all the development - software you need to build your own uClibc applications, including: bash, awk, - make, gcc, g++, autoconf, automake, ncurses, zlib, openssl, openssh, gdb, - strace, busybox, GNU coreutils, GNU tar, GNU grep, etc. - -

- - Each of these uClibc development systems was created using - buildroot. - -

- - These development systems should provide pretty much everything you need to get - started building your own applications with uClibc. Once you download one of - these systems, you can then boot into it, loop mount it, dd it to a spare drive - and use a tool such as resize2fs to make it fill a partition... Whatever works - best for you. - -

- The quickest way to get started using a root_fs image (using the i386 - platform as an example) is: -

- Type "exit" to end the chroot session and return to the host system. -

- - - -

-

-

I think I found a bug in uClibc! What should I do?

-

- - If you find a problem with uClibc, please submit a detailed bug report to - the uClibc mailing list at - uclibc@mail.uclibc.org. Please do not send private email to Erik - (the maintainer of uClibc) asking for private help unless you are planning - on paying for consulting services. When we answer questions on the uClibc - mailing list, it helps everyone, while private answers help only you... - - A well-written bug report should include an example that demonstrates the - problem behaviors and enables anyone else to duplicate the bug on their own - machine. For larger applications where it may prove difficult to provide - an example application, we recommend that you use a tool such as gdb, - strace, ltrace, and or valgrind to create a logfile showing the problem - behavior. - - -

-

-

My package builds fine but link fails with errors like - "undefined reference to __fputc_unlocked", who do I blame?!

-

- - This error crops up when a build system mixes system headers (say glibc) - with the target headers (say uClibc). Make sure your build system is not - including extraneous include options (-I) and double check that it is using - the correct compiler. Many build systems incorrectly force things like - -I/usr/include or -I/usr/local/include or -I${prefix}/include (which usually - just expands to -I/usr/include). - - -

-

-

My package builds fine but link fails with errors like "undefined reference - to rpl_realloc / rpl_malloc", who do I blame?!

-

- - This error crops up because you didn't enable MALLOC_GLIBC_COMPAT support. - Configure scripts detect whether your libc supports "GNU malloc" features by - seeing whether malloc(0) returns NULL (glibc malloc(0) will return a non NULL - pointer). uClibc defaults to malloc(0) returning NULL so autoconf will assume - malloc from your libc sucks and procede to try and compile the malloc replacement - version in the gnulib addon. However, since not many packages include gnulib, - they will fail to link with rpl_realloc / rpl_malloc errors. You could force - configure to assume working behavior by exporting the variables 'jm_cv_func_working_malloc' - (older autoconf) and 'ac_cv_func_malloc_0_nonnull' (newer autoconf) to 'yes' - before running `./configure`. - - -

-

-

Why do I keep getting "sh: can't access tty; job control - turned off" errors? Why doesn't Control-C work within my shell?

-

- - This isn't really a uClibc question, but I'll answer it here anyways. Job - control will be turned off since your shell can not obtain a controlling - terminal. This typically happens when you run your shell on /dev/console. - The kernel will not provide a controlling terminal on the /dev/console - device. Your should run your shell on a normal tty such as tty1 or ttyS0 - and everything will work perfectly. If you REALLY want your shell - to run on /dev/console, then you can hack your kernel (if you are into that - sortof thing) by changing drivers/char/tty_io.c to change the lines where - it sets "noctty = 1;" to instead set it to "0". I recommend you instead - run your shell on a real console... - - -

-

-

How do I make autoconf and automake behave?

-

- - When you are cross-compiling, autoconf and automake are known to behave - badly. This is because a large number of configure scripts (such as the - one from openssh) try to actually execute applications that were cross - compiled for your target system. This is bad, since of course these won't - run, and this will also prevent your programs from compiling. You need to - complain to the authors of these programs and ask them to fix their broken - configure scripts. - - -

-

-

When I run 'ldd' to get a list of the library dependencies - for a uClibc binary, ldd segfaults! What should I do?

-

- - Use the ldd that is built by uClibc, not your system's one. You can build - uClibc'd ldd for your host system by going into the uClibc/utils/ directory - in the uClibc source and running 'make ldd.host'. -

- - When your system's ldd looks for library dependencies, it actually _runs_ - that program. This works fine -- usually. It generally will not work at - all when you have been cross compiling (which is why ldd segfaults). The - ldd program created by uClibc is cross platform and doesn't mind at all if - it cannot execute the target program. If you use the uClibc version of - 'ldd', it will do the right thing and produce correct results, even when it - is used on cross compiled binaries. - - -

-

-

Why does localtime() return times in UTC even when I have my timezone set?

-

- - - The uClibc time functions get timezone information from the TZ environment - variable, as described in the Single Unix Specification Version 3. See - - http://www.opengroup.org/onlinepubs/007904975/basedefs/xbd_chap08.html - for details on valid settings of TZ. For some additional examples, read - - http://www.uclibc.org/lists/uclibc/2002-August/004010.html in the uClibc - mailing list archive. - You can store the value of TZ in the file '/etc/TZ' and uClibc will then - automagically use the specified setting. - - -

-

-

What is the history of uClibc? Where did it come from?

-

- - - uClibc started off as a fork on the Linux-8086 C library, which is - part of the elks project. - The Linux-8086 C library was, apparently, largely written from scratch but - also borrowed code from libc4, glibc, some Atari library code, with bits - and pieces from about 20 other places. - -

- - I had for some time been despairing over the state of C libraries in Linux. - GNU libc, the standard, is very poorly suited to embedded systems and has - been getting bigger with every release. I spent quite a bit of time - looking over the available Open Source C libraries that I knew of, and none - of them really impressed me. I felt there was a real vacancy in the - embedded Linux ecology. The closest library to what I imagined an embedded - C library should be was uClibc. But it had a lot of problems too -- not - the least of which was that, traditionally, uClibc required a complete - source tree fork in order to support each and every new platform. This - resulted in a big mess of twisty versions, all different. I decided to fix - it and the result is what you see here. - -

- - To start with, (with some initial help from D. Jeff Dionne), I ported - uClibc to run on i386. I then grafted in the header files from glibc and - cleaned up the resulting breakage. This (plus some additional work) has - made it much less dependant on kernel headers, a large departure from its - traditional tightly-coupled-to-the-kernel origins. I have written and/or - rewritten a number of things that were missing or broken, and sometimes - grafted in bits of code from the current glibc and libc5. I have also - added a proper configuration system which allows you to easily select your - target architecture and enable and disable various features. Many people - have helped by testing, contributing ports to new architectures, and adding - support for missing features. - -

- - In particular, around the end of 2000, Manuel Novoa III got involved with - uClibc. One of his first contributions was the original gcc wrapper (which - has since been removed). Since then, he has written virtually all of the - current uClibc stdio, time, string, ctype, locale, and wchar-related code, - as well as much of stdlib and various other bits throught the library. - -

- - These days, uClibc is being developed and enhanced by Erik Andersen - and Manuel Novoa III of - CodePoet Consulting - along with the rest of the embedded Linux community. - - - -

-

-

I demand that you to add <favorite feature> right now! How come - you don't answer all my questions on the mailing list instantly? I demand - that you help me with all of my problems Right Now!

-

- - You have not paid us a single cent and yet you still have the - product of several years of work from Erik and Manuel and - many other people. We are not your slaves! We work on uClibc - because we find it interesting. If you go off flaming us, we will - ignore you. - - - -

-

-

I need help with uClibc! What should I do?

-

- - If you find that you need help with uClibc, you can ask for help on the - uClibc mailing list at uclibc@mail.uclibc.org. In addition to the uClibc - mailing list, Erik and Manuel are also known to sometimes hang out on the - uClibc IRC channel: #uclibc on irc.freenode.net. - -

- - Please do not send private email to Erik and/or Manuel asking for - private help unless you are planning on paying for consulting services. - When we answer questions on the uClibc mailing list, it helps everyone - since people with similar problems in the future will be able to get help - by searching the mailing list archives. Private help is reserved as a paid - service. If you need to use private communication, or if you are serious - about getting timely assistance with uClibc, you should seriously consider - paying for consulting time. - -

- - - -

-

-

I need you to add <favorite feature>! Are the uClibc developers willing to - be paid in order to fix bugs or add in <favorite feature>? Are you willing to provide - support contracts?

-

- - Sure! Now you have our attention! What you should do is contact Erik Andersen of CodePoet Consulting to bid - on your project. If Erik is too busy to personally add your feature, there - are several other active uClibc contributors who will almost certainly be able - to help you out. Erik can contact them and ask them about their availability. - - -

-

-

I think you guys are great and I want to help support your work!

-

- - Wow, that would be great! You can click here to help support uClibc and/or request features. - - -

-
- - - - - - -
-
- - - If you prefer to contact us directly for payments, hardware donations, - support requests, etc., you can contact - CodePoet Consulting here. - -
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