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| author | Eric Andersen <andersen@codepoet.org> | 2001-12-20 14:23:44 +0000 |
|---|---|---|
| committer | Eric Andersen <andersen@codepoet.org> | 2001-12-20 14:23:44 +0000 |
| commit | 3deb1308865cc114984e9396af2ff80daa186a1b (patch) | |
| tree | 45f1877eb9be4b35472d9d787d3af3fa7a62fb86 /docs/uclibc.org/FAQ.html | |
| parent | 5e62bc31b1f97a9974109c726f5667f4df9995e7 (diff) | |
Update the docs and website
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| -rw-r--r-- | docs/uclibc.org/FAQ.html | 436 |
1 files changed, 436 insertions, 0 deletions
diff --git a/docs/uclibc.org/FAQ.html b/docs/uclibc.org/FAQ.html new file mode 100644 index 000000000..92b227edb --- /dev/null +++ b/docs/uclibc.org/FAQ.html @@ -0,0 +1,436 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd"> + +<HTML> +<HEAD> + <TITLE>uClibc FAQ-- a C library for embedded systems</TITLE> +</HEAD> + +<body text="#000000" alink="#660000" link="#660000" bgcolor="#dee2de" vlink="#660000"> + +<basefont face="lucida, helvetica, arial" size="3"> + + +<CENTER> +<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> +<p> + + +<!-- Begin NOT Working List --> + + +<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"> + +<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> + +<p> +<TR><TD BGCOLOR="#ccccc0" ALIGN=left> + <B> + What platforms does uClibc run on? + </B> +</TD></TR> +<TR><TD BGCOLOR="#eeeee0"> + + Currently uClibc runs on arm, i386, m68k, mipsel, powerpc, sh, + sparc, and v850. + + +<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. + + + +<p> +<TR><TD BGCOLOR="#ccccc0" ALIGN=left> + <B> + Why is it called uClibc? + </B> +</TD></TR> +<TR><TD BGCOLOR="#eeeee0"> + + 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 you uClibc is simply the microcontroller C library. + This is because uClibc was originaly created to support uClinux, a port of + Linux for MMU-less microcontrollers such as the Dragonball, Coldfire, and + ARM7TDMI. For simplicity, it is pronounced "yew-see-lib-see". + + + +<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 using it on + your development system, you can be sure that the code you are working on + will actually run when you deploy it your target system. + + + +<p> +<TR><TD BGCOLOR="#ccccc0" ALIGN=left> + <B> + Why are you doing this? Whats wrong with glibc? + </B> +</TD></TR> +<TR><TD BGCOLOR="#eeeee0"> + + The inital reason, was that glibc does not support MMU-less systems. But + also because uClibc is so much smaller then the GNU C library. The GNU C + library has a different set of goals then uClibc. The GNU C library is a + great piece of software. It complies with just about every standard ever + created, and runs on just about every operating system as well -- 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 whether we support MS-DOS, or Cygwin, + or any other system. This lets us cut out lots 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 Specificaion, + version 2. Well, standards are important. But so is pragmatism. The + wordexp function is huge, and yet I am not aware of even one Linux + application that uses wordexp. So uClibc doesn't provide wordexp(). There + are many similar examples. + + Glibc is a general purpose C library, and so as policy things are optimized + for speed. Most of uClibc's routines have been very carefuly written to + optimize them for size instead of speed. + + 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. + + + +<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 system, and you are tight on space, then + using uClibc instead if glibc should allow you to use your storage for + other things. + + If you are trying to build a ultra fast fileserver for your company that + has 12 Terabytes of storage, then you probably want to use glibc... + + + +<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? + </B> +</TD></TR> +<TR><TD BGCOLOR="#eeeee0"> + + No, you do not need to give away your source code just because you use + uClibc and/or run on Linux. + + + +<p> +<TR><TD BGCOLOR="#ccccc0" ALIGN=left> + <B> + I want to create a closed source commercial application using uClibc. + Is that legal? + </B> +</TD></TR> +<TR><TD BGCOLOR="#eeeee0"> + + Yes. 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. :-) + + If you are staticly linking your closed source commercial application with + uClibc, then you must take additional steps to comply with the uClibc + license. You can sell your application as usual, but you must also make + your closed source application available to your customers as an object + file which can then be linked with updated versions of uClibc. This will + (in theory) allow your customers to later link with updated versions of + uClibc. 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 stuff? + </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 architecture) and it will automagically + make your program 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 dependancies for a uClibc + binary, ldd segfault! Or it runs my application? Anyways, it doesn't + work! 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 the library dependancies, it actually tries to + _execute_ that program. This works fine -- usually. I doesn't work at all + when you are cross compiling (thats why ldd segfaults). The ldd program + created by uClibc is cross platform and doesn't actually try to run the + target program like your system one does, so it should do the right thing, + and 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"> + + This 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>. + <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 it just + gets bigger with every release). I spent quite a bit of time looking over the + other 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 that 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, resulting 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. + + <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 independant 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. + + + +<p> +<TR><TD BGCOLOR="#ccccc0" ALIGN=left> + <B> + I need you to add <favorite feature> now! How come you don't answer all my + questions on the mailing list withing 5 minutes? I demand that you help me <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 + over year and a half of work from Erik and Manuel and lots of other people. + How dare you treat us that way! We work on uClibc because we find it + interesting. If you go off flaming us, we will ignore you. + + + +<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 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 may be able to help you out. + Erik can contact them and ask them about their availability. + + +<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. + + <!-- Begin PayPal Logo --> + <center> + <form action="https://www.paypal.com/cgi-bin/webscr" method="post"> + <input type="hidden" name="cmd" value="_xclick"> + <input type="hidden" name="business" value="andersen@codepoet.org"> + <input type="hidden" name="item_name" value="Support uClibc and/or request features"> + <input type="hidden" name="image_url" value="https://codepoet-consulting.com/images/codepoet.png"> + <input type="hidden" name="no_shipping" value="1"> + <input type="image" src="images/donate.png" border="0" name="submit" alt="Make donation using PayPal"> + </form> + </center> + <!-- End PayPal Logo --> + + If you prefer to contact us directly for payments (we have a credit card machine so + you can avoid online payments), 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"> +</TD></TR> +</TABLE> +</P> + +<a href="http://uclibc.org/">Well then, click here to return to the uClibc home page.</a> + + +<!-- Footer --> +<HR> +<TABLE WIDTH="100%"> + <TR> + <TD> + <font size="-1" face="arial, helvetica, sans-serif"> + Mail all comments, insults, suggestions and bribes to + <a href="mailto:andersen@codepoet.org">Erik Andersen</a><BR> + </font> + </TD> + + <TD> + <a href="http://www.vim.org"><img border=0 width=90 height=36 + src="images/written.in.vi.png" + alt="This site created with the vi editor"></a> + </TD> + + <TD> + <a href="http://www.gimp.org/"><img border=0 width=90 height=36 + src="images/gfx_by_gimp.png" alt="Graphics by GIMP"></a> + </TD> + + <TD> + <a href="http://www.linuxtoday.com"><img width=90 height=36 + src="images/ltbutton2.png" alt="Linux Today"></a> + </TD> + + <TD> + <p><a href="http://slashdot.org"><img width=90 height=36 + src="images/sdsmall.png" alt="Slashdot"></a> + </TD> + + <TD> + <a href="http://freshmeat.net"><img width=90 height=36 + src="images/fm.mini.png" alt="Freshmeat"></a> + </TD> + + </TR> +</TABLE> + + +</CENTER> +</BODY> +</HTML> + + + |