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- <TITLE>uClibc FAQ-- a C library for embedded systems</TITLE>
-</HEAD>
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-
-<basefont face="lucida, helvetica, arial" size="3">
+<h3>Frequently Asked Questions</h3>
+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,
-<CENTER>
+<ol>
+<li><a href="#naming">Why is it called uClibc?</a>
+<li><a href="#platforms">What platforms does uClibc run on?</a>
+<li><a href="#why">Why are you doing this? What's wrong with glibc?</a>
+<li><a href="#doesnt_suck">So uClibc is smaller then glibc? Doesn't that mean it
+ completely sucks? How could it be smaller and not suck?</a>
+<li><a href="#why_should_i">Why should I use uClibc?</a>
+<li><a href="#licensing">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.</a>
+<li><a href="#development">Can I use it on my x86 development system?</a>
+<li><a href="#shared"> Does uClibc support shared libraries?</a>
+<li><a href="#compiling">How do I compile programs with uClibc?</a>
+<li><a href="#toolchain">Do I really need to build a uClibc toolchain?</a>
+<li><a href="#wrapper">What happened to the old toolchain wrapper?</a>
+<li><a href="#dev_systems">Is a pre-compiled uClibc development system available?</a>
+<li><a href="#bugs">I think I found a bug in uClibc! What should I do?!</a>
+<li><a href="#miscompile">My package builds fine but link fails with errors like "undefined reference
+ to __fputc_unlocked", who do I blame?!</a>
+<li><a href="#gnu_malloc">My package builds fine but link fails with errors like "undefined reference
+ to rpl_realloc / rpl_malloc", who do I blame?!</a>
+<li><a href="#job_control">Why do I keep getting "sh: can't access tty; job control
+ turned off" errors? Why doesn't Control-C work within my shell?</a>
+<li><a href="#autoconf">How do I make autoconf and automake behave?</a>
+<li><a href="#ldd">When I run 'ldd' to get a list of the library dependencies
+ for a uClibc binary, ldd segfaults! What should I do?</a>
+<li><a href="#timezones">Why does localtime() return times in UTC even when I have my timezone set?</a>
+<li><a href="#history">What is the history of uClibc? Where did it come from?</a>
+<li><a href="#demanding">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 <em>Right Now</em>!</a>
+<li><a href="#helpme">I need help with uClibc! What should I do?</a>
+<li><a href="#contracts">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?</a>
+<li><a href="#support">I think you guys are great and I want to help support your work!</a>
+
+
+</ol>
+
+
+<hr />
+<p>
+<h2><a name="naming">Why is it called uClibc?</a></h2>
<p>
-<TABLE BORDER=0 CELLSPACING=1 CELLPADDING=2>
- <TR>
- <td bgcolor="#000000">
- <FONT FACE="lucida, helvetica" COLOR="#ccccc0">
- <B>µ C l i b c</B>
- </FONT>
- </TD>
- </TR>
-</TABLE>
+ 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".
+ <p>
+ The name is partly historical, since uClibc was originally
+ created to support <a href="http://www.uclinux.org">µClinux</a>, 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.
+
+<hr />
+<p>
+<h2><a name="platforms">What platforms does uClibc run on?</a></h2>
<p>
-<!-- Begin NOT Working List -->
+ Currently uClibc runs on alpha, ARM, cris, i386, i960, h8300,
+ m68k, mips/mipsel, PowerPC, SH, SPARC, and v850 processors.
-<TABLE WIDTH=95% CELLSPACING=1 CELLPADDING=4 BORDER=1>
-<TR><TD BGCOLOR="#ccccc0" ALIGN=center>
- <A NAME="notworking"> <BIG><B>
- uClibc Frequently Asked Questions (FAQ)
- </font>
- </A></B></BIG>
-</TD></TR>
-<TR><TD BGCOLOR="#eeeee0">
+<hr />
+<p>
+<h2><a name="why">Why are you doing this? What's wrong with glibc?</a></h2>
+<p>
+
+ 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
+
-<p>
-This is a collection of some of the 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,
-<br>
-When you are done, <a href="http://uclibc.org/">you can click here to return
-to the uClibc home page.</a>
+<hr />
<p>
-<TR><TD BGCOLOR="#ccccc0" ALIGN=left>
- <B>
- What platforms does uClibc run on?
- </B>
-</TD></TR>
-<TR><TD BGCOLOR="#eeeee0">
+<h2><a name="doesnt_suck">So uClibc is smaller then glibc? Doesn't that mean it completely sucks?
+How could it be smaller and not suck?</a></h2>
+<p>
+<p>
+
+ 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.
+
+ <p>
+
+ 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.
+
+ <p>
+
+ 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.
+
+ <p>
+
+ 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!!!
+
+ <p>
- Currently uClibc runs on arm, i386, h8300, m68k, mips, mipsel, powerpc,
- sh, sparc, and v850.
-
+ 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.
+
+<hr />
+<p>
+<h2><a name="why_should_i">Why should I use uClibc?</a></h2>
<p>
-<TR><TD BGCOLOR="#ccccc0" ALIGN=left>
- <B>
- Does uClibc support shared libraries?
- </B>
-</TD></TR>
-<TR><TD BGCOLOR="#eeeee0">
-
- Yes. uClibc has shared library support on x86, arm, and powerpc.
- Shared Libraries are _not_ currently supported on MMU-less systems.
+
+ 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.
+
+ <p>
+
+ 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...
+<hr />
<p>
-<TR><TD BGCOLOR="#ccccc0" ALIGN=left>
- <B>
- Why is it called uClibc?
- </B>
-</TD></TR>
-<TR><TD BGCOLOR="#eeeee0">
+<h2><a name="licensing">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.</a></h2>
+<p>
+
+ 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 <a
+ href="http://www.gnu.org/copyleft/lesser.html">Lesser GPL</a> licence, just
+ like the GNU C library (glibc). Please read this licence, or have a lawyer
+ read this licence 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! :-)
+ <p>
- For simplicity, uClibc is pronounced "yew-see-lib-see". 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 uClibc is sortof an abbreviation for "the
- microcontroller C library". This is partly historical, since
- uClibc was originally created to support <a href="http://www.uclinux.org">µClinux</a>, a port of Linux
- for MMU-less microcontrollers such as the Dragonball, Coldfire, and
- ARM7TDMI. These days, uClibc works just fine with normal Linux
- system (like on x86, strongArm, and powerpc).
+ 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.
+ <p>
+ 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.
+<hr />
+<p>
+<h2><a name="development">Can I use it on my x86 development system?</a></h2>
<p>
-<TR><TD BGCOLOR="#ccccc0" ALIGN=left>
- <B>
- Can I use it on my desktop x86 system?
- </B>
-</TD></TR>
-<TR><TD BGCOLOR="#eeeee0">
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
+ the code you are working on will actually run when you deploy it on
your target system.
+
+<hr />
+<p>
+<h2><a name="shared"> Does uClibc support shared libraries?</a></h2>
<p>
-<TR><TD BGCOLOR="#ccccc0" ALIGN=left>
- <B>
- Why are you doing this? What's wrong with glibc?
- </B>
-</TD></TR>
-<TR><TD BGCOLOR="#eeeee0">
-
- Initially, the project began because glibc does not support
- MMU-less systems. But uClibc is also very useful because it is so
- much smaller then the GNU C library. 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 to
- 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
-
-
-
-<p>
-<TR><TD BGCOLOR="#ccccc0" ALIGN=left>
- <B>
- So uClibc is smaller then glibc? Doesn't that mean it completely sucks?
- How could it be smaller and not suck?
- </B>
-</TD></TR>
-<TR><TD BGCOLOR="#eeeee0">
-
- 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 Cygwin, or AmigaOs any other system. This lets us cut out
- a lot of complexity and very carefully optimize for Linux. By very
- careful design, we can also take a few shortcuts. For example, glibc
- contains an implementation of the wordexp() function, in compliance
- with the Single Unix Specification, version 2. Well, standards are
- important. But so is pragmatism. The wordexp function is huge, yet I
- am not aware of even one Linux application that uses it! So uClibc
- doesn't provide wordexp(). There are many similar examples. In other
- cases, uClibc leaves certain features (such as full C99 Math library
- support, IPV6, and RPC support) disabled by default. Those features
- can be enabled for people that need them, but are otherwise disabled to
- save space.
+ 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.
<p>
+ Shared Libraries are not currently supported by uClibc on MMU-less systems.
+ <a href="http://www.snapgear.com/">SnapGear</a> 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.
+
+
+<hr />
+<p>
+<h2><a name="compiling">How do I compile programs with uClibc?</a></h2>
+<p>
- Glibc is a general purpose C library, and so as policy things are optimized
- for speed. Most of uClibc's routines have been very carefully written to
- optimize them for size instead.
+ You will need to have your own uClibc toolchain. A toolchain consists
+ of <a href="http://sources.redhat.com/binutils/">GNU binutils</a>,
+ <a href="http://gcc.gnu.org/">the gcc compiler</a>, and uClibc, all
+ built to produce binaries for your target system linked with uClibc.
+ You can build your own native uClibc toolchain using the
+ <a href="http://buildroot.uclibc.org/">uClibc buildroot system</a>.
<p>
+ To build your own uClibc toolchain, follow the following simple
+ steps:
+ <ul>
+ <li> Point your web browser <a href="http://buildroot.uclibc.org/">here</a>,
+ <li> Download of copy of buildroot
+ <li> Unpack the tarball on your Linux system somewhere
+ <li> Edit the Makefile as needed if you wish to change anything.
+ <li> run 'unset CC'. Then run 'unset CXX'. Some Linux systems
+ (i.e. Gentoo) set variables such as 'CC' in the system environment
+ which really messes things up when cross compiling.
+ <li> run 'make menuconfig'
+ <li> Select the things you want to build. If you <em>only</em> want a
+ toolchain, leave everything except the toolchain disabled.
+ <li> save your buildroot configuration.
+ <li> run 'make'
+ <li> go eat a nice wholesome sandwich, drink a pop, call a friend,
+ play a video game, and generally find something to do. While you
+ are waiting, buildroot will download all the needed source code and
+ then compile things up for you.
+ <li> You should now have a shiny new toolchain, and maybe even a shiny
+ new uClibc based root filesystem or development system, depending on
+ the options you selected.
+ </ul>
+
+<hr />
+<p>
+<h2><a name="toolchain">Do I really need to build a uClibc toolchain?</h2>
+<p>
- 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, but is many times smaller.
+ 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
+ <a href="http://buildroot.uclibc.org/">uClibc buildroot system</a>,
+ which makes it easy to build your own uClibc toolchain and/or an initial
+ uClibc based system.
+
+ <p>
+ 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.
-
+<hr />
+<p>
+<h2><a name="wrapper">What happened to the old toolchain wrapper?</h2>
<p>
-<TR><TD BGCOLOR="#ccccc0" ALIGN=left>
- <B>
- Why should I use uClibc?
- </B>
-</TD></TR>
-<TR><TD BGCOLOR="#eeeee0">
- 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.
+ 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.
- If you are trying to build a huge fileserver for your company that will
- have 12 Terabytes of storage, then using glibc may make more sense...
+ <p>
+
+ 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.
+ <p>
+ Some discussion on the reasoning behind this decision can be found here:
+ <a href="http://www.uclibc.org/lists/uclibc/2003-October/007315.html">
+ http://www.uclibc.org/lists/uclibc/2003-October/007315.html</a>
+ in the uClibc mailing list archives.
+<hr />
<p>
-<TR><TD BGCOLOR="#ccccc0" ALIGN=left>
- <B>
- I want to create a closed source commercial application and I want to
- protect my intellectual property. If I use uClibc, don't I have to
- release all my source code for free? Is that legal?
- </B>
-</TD></TR>
-<TR><TD BGCOLOR="#eeeee0">
+<h2><a name="dev_systems">Is a pre-compiled uClibc development system available?</a></h2>
+<p>
+
+ If you want to be <em>really</em> 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
+
+ <a href="http://www.uclibc.org/downloads/root_fs_arm.ext2.bz2">arm</a>,
+ <a href="http://www.uclibc.org/downloads/root_fs_armeb.ext2.bz2">armeb</a>,
+ <a href="http://www.uclibc.org/downloads/root_fs_i386.ext2.bz2">i386</a>,
+ <a href="http://www.uclibc.org/downloads/root_fs_mips.ext2.bz2">mips</a>,
+ <a href="http://www.uclibc.org/downloads/root_fs_mipsel.ext2.bz2">mipsel</a>,
+ <a href="http://www.uclibc.org/downloads/root_fs_powerpc.ext2.bz2">powerpc</a>, and
+ <a href="http://www.uclibc.org/downloads/root_fs_sh4.ext2.bz2">sh4</a>.
+
+ <p>
+
+ 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.
+
+ <p>
+
+ Each of these uClibc development systems was created using
+ <a href="http://buildroot.uclibc.org/">buildroot</a>, specifically,
+ <a href="http://www.uclibc.org/downloads/buildroot.tar.bz2">buildroot.tar.bz2</a>
+ along with <a href="http://www.uclibc.org/downloads/buildroot-sources">these sources</a>.
+
+ <p>
- No, you do not need to give away your source code just because you use
- uClibc and/or run on Linux. uClibc is licensed under the LGPL, just
- like GNU libc. If you are using uClibc as a shared library, then your
- closed source application is 100% legal. Please consider sharing some
- of the money you make with us! :-)
+ 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.
<p>
-
- If you are statically linking your closed source application with
- uClibc, then you must take additional steps to comply with the uClibc
- license. You may sell your statically linked application as usual, but
- you must also make your application available to your customers 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.
-
-
-<p>
-<TR><TD BGCOLOR="#ccccc0" ALIGN=left>
- <B>
- How do I compile programs with uClibc?
- </B>
-</TD></TR>
-<TR><TD BGCOLOR="#eeeee0">
-
- The easiest way is to use the compiler wrapper built by uClibc. Instead of
- using your usual compiler or cross compiler, you can use i386-uclibc-gcc,
- (or whatever is appropriate for your target architecture) and your
- applications will auto-magically link against uClibc.
-
-
-
-<p>
-<TR><TD BGCOLOR="#ccccc0" ALIGN=left>
- <B>
- How do I make autoconf and automake behave?
- </B>
-</TD></TR>
-<TR><TD BGCOLOR="#eeeee0">
-
- First run
- <pre>export PATH=/usr/i386-linux-uclibc/bin:$PATH</pre>
- (or similar adjusted for your target architecture) then run you can simply
- run autoconf/automake and it should _just work_.
-
-
-
-<p>
-<TR><TD BGCOLOR="#ccccc0" ALIGN=left>
- <B>
- When I run 'ldd' to get a list of the library dependencies for a uClibc
- binary, ldd segfaults! What should I do?
- </B>
-</TD></TR>
-<TR><TD BGCOLOR="#eeeee0">
-
- Use the ldd that is built by uClibc, not your system's one. When your
- system's ldd looks for library dependencies, it actually _runs_ that
- program. This works fine -- usually. It doesn't 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 even try to run
- the target program (like your system one does). So use the uClibc one
- and it will do the right thing, and it won't segfault even when you are
- cross compiling.
-
-
-<p>
-<TR><TD BGCOLOR="#ccccc0" ALIGN=left>
- <B>
- What is the history of uClibc? Where did it come from?
- </B>
-</TD></TR>
-<TR><TD BGCOLOR="#eeeee0">
-
- The history and origin of uClibc is long and twisty.
- In the beginning, there was <a href="http://www.gnu.org/software/libc/libc.html">GNU libc</a>. Then, libc4
- (which later became linux libc 5) forked from GNU libc version 1.07.4, with
- additions from 4.4BSD, in order to support Linux. Later, the <a
- href="http://www.cix.co.uk/~mayday/">Linux-8086 C library</a>, which is part of
- the <a href="http://www.elks.ecs.soton.ac.uk/">elks project</a>, was created,
- which 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. Then uClibc forked off from the Linux-8086 C library in order to run
- on <a href="http://www.uclinux.org">µClinux</a>.
+ The quickest way to get started using a root_fs image (using the i386
+ platform as an example) is:
+ <ul>
+ <li>Download root_fs_i386.bz2 from uclibc.org</li>
+ <li>bunzip2 root_fs_i386.bz2</li>
+ <li>mkdir root_fs</li>
+ <li>su root</li>
+ <li>mount -o loop root_fs_i386 root_fs</li>
+ <li>chroot root_fs /bin/su -</li>
+ </ul>
+ Type "exit" to end the chroot session and return to the host system.
+ <p>
+
+
+
+<hr />
+<p>
+<h2><a name="bugs">I think I found a bug in uClibc! What should I do?</h2>
+<p>
+
+ If you find a problem with uClibc, please submit a detailed bug report to
+ the uClibc mailing list at <a href="mailto:uclibc@mail.uclibc.org">
+ uclibc@mail.uclibc.org</a>. 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.
+
+
+<hr />
+<p>
+<h2><a name="miscompile">My package builds fine but link fails with errors like
+ "undefined reference to __fputc_unlocked", who do I blame?!</h2>
+<p>
+
+ 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).
+
+
+<hr />
+<p>
+<h2><a name="gnu_malloc">My package builds fine but link fails with errors like "undefined reference
+ to rpl_realloc / rpl_malloc", who do I blame?!</h2>
+<p>
+
+ 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`.
+
+
+<hr />
+<p>
+<h2><a name="job_control">Why do I keep getting "sh: can't access tty; job control
+ turned off" errors? Why doesn't Control-C work within my shell?</a></h2>
+<p>
+
+ 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 <em>REALLY</em> 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...
+
+
+<hr />
+<p>
+<h2><a name="autoconf">How do I make autoconf and automake behave?</a></h2>
+<p>
+
+ 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.
+
+
+<hr />
+<p>
+<h2><a name="ldd">When I run 'ldd' to get a list of the library dependencies
+ for a uClibc binary, ldd segfaults! What should I do?</a></h2>
+<p>
+
+ 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'.
+ <p>
+
+ 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.
+
+
+<hr />
+<p>
+<h2><a name="timezones">Why does localtime() return times in UTC even when I have my timezone set?</a></h2>
+<p>
+
+
+ The uClibc time functions get timezone information from the TZ environment
+ variable, as described in the Single Unix Specification Version 3. See
+ <a href="http://www.opengroup.org/onlinepubs/007904975/basedefs/xbd_chap08.html">
+ http://www.opengroup.org/onlinepubs/007904975/basedefs/xbd_chap08.html</a>
+ for details on valid settings of TZ. For some additional examples, read
+ <a href="http://www.uclibc.org/lists/uclibc/2002-August/004010.html">
+ http://www.uclibc.org/lists/uclibc/2002-August/004010.html</a> 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.
+
+
+<hr />
+<p>
+<h2><a name="history">What is the history of uClibc? Where did it come from?</a></h2>
+<p>
+
+
+ uClibc started off as a fork on the <a
+ href="http://www.cix.co.uk/~mayday/">Linux-8086 C library</a>, which is
+ part of the <a href="http://www.elks.ecs.soton.ac.uk/">elks project</a>.
+ 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.
+
<p>
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 (listed below), 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 had 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.
- My source tree has now become the official uClibc source tree and it now lives
- on cvs.uclinux.org and www.uclibc.org.
+ 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.
<p>
To start with, (with some initial help from <a
- href="http://www.uclinux.org/developers/index.html">D. Jeff Dionne</a>), I
- ported it to run on x86. I then grafted in the header files from glibc 2.1.3
- and cleaned up the resulting breakage. This (plus some additional work) has
- made it almost completely independent of 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 built a proper
- platform abstraction layer, so now you can simply edit the file "Config" and
- use that to decide which architecture you will be compiling for, and whether or
- not your target has an MMU, and FPU, etc. I have also added a test suite,
- which, though incomplete, is a good start. Several people have helped by
- contributing ports to new architectures, and a lot of work has been done on
- adding support for missing features.
+ href="http://www.uclinux.org/developers/">D. Jeff Dionne</a>), 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.
+
+ <p>
+
+ 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.
<p>
- These days, uClibc is being developed and enhanced by Erik Andersen of
- <a href="http://codepoet-consulting.com/">CodePoet Consulting</a> along
- with the rest of the embedded Linux community.
+ These days, uClibc is being developed and enhanced by Erik Andersen
+ and Manuel Novoa III of
+ <a href="http://codepoet-consulting.com/">CodePoet Consulting</a>
+ along with the rest of the embedded Linux community.
+<hr />
+<p>
+<h2><a name="demanding">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 <em>Right Now</em>!</a></h2>
<p>
-<TR><TD BGCOLOR="#ccccc0" ALIGN=left>
- <B>
- 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 <em>Right Now</em>!
- </B>
-</TD></TR>
-<TR><TD BGCOLOR="#eeeee0">
You have not paid us a single cent and yet you still have the
- product of nearly two years of work from Erik and Manuel and
+ 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.
+
+<hr />
+<p>
+<h2><a name="helpme">I need help with uClibc! What should I do?</a></h2>
+<p>
+
+ 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.
+
+ <p>
+
+ <b>Please do not send private email to Erik and/or Manuel asking for
+ private help unless you are planning on paying for consulting services.</b>
+ 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.
+
+ <p>
+
+
+
+<hr />
+<p>
+<h2><a name="contracts">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?</a></h2>
<p>
-<TR><TD BGCOLOR="#ccccc0" ALIGN=left>
- <B>
- 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?
- </B>
-</TD></TR>
-<TR><TD BGCOLOR="#eeeee0">
Sure! Now you have our attention! What you should do is contact <a
href="mailto:andersen@codepoet.org">Erik Andersen</a> of <a
href="http://codepoet-consulting.com/">CodePoet Consulting</a> 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
+ 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.
-
-
+
+
+<hr />
+<p>
+<h2><a name="support">I think you guys are great and I want to help support your work!</a></h2>
<p>
-<TR><TD BGCOLOR="#ccccc0" ALIGN=left>
- <B>
- I think you guys are great and I want to help support your work!
- </B>
-</TD></TR>
-<TR><TD BGCOLOR="#eeeee0">
Wow, that would be great! You can click here to help support uClibc and/or request features.
-
+
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- <input type="image" src="images/donate.png" border="0" name="submit" alt="Make donation using PayPal">
+ <input type="image" src="images/donate.png" name="submit" alt="Make donation using PayPal">
</form>
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- If you prefer to contact us directly for payments (Erik has a credit card machine so
- you can avoid making payments online), hardware donations, support requests, etc., you can
- contact <a href="http://codepoet-consulting.com/">CodePoet Consulting</a> here.
-
-<p>
-<TR><TD BGCOLOR="#ccccc0" ALIGN=left>
- <B>
- Ok, I'm done reading all these questions.
- </B>
-</TD></TR>
-<TR><TD BGCOLOR="#eeeee0">
-
-<a href="http://uclibc.org/">Well then, click here to return to the uClibc home page.</a>
-
-
-
-<!-- End things -->
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- </font>
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+ If you prefer to contact us directly for payments, hardware donations,
+ support requests, etc., you can contact
+ <a href="http://codepoet-consulting.com/">CodePoet Consulting</a> here.
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