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authorEric Andersen <andersen@codepoet.org>2001-11-24 10:17:24 +0000
committerEric Andersen <andersen@codepoet.org>2001-11-24 10:17:24 +0000
commitdfb5fe2dee1b64c57c3df7fc4c0ecb7ad0450730 (patch)
treecc3db9a916b8d9821f142b97a3200bad61c3975e /FAQ.txt
parent1df709beaf6f88e7906d427be4f0c7dcf12e8a55 (diff)
Move the FAQ. Add a docs dir. Add in a report on thread support.
-Erik
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-This is a collection of some of the frequently asked question
-about uClibc. Some of the questions even have answers. If you
-have additions to this FAQ document, I'd love to add them,
-
- -Erik
-
-
-Q: Why is it called uClibc?
-
- The letter 'u' is short for the greek letter "mu". "Mu" stands for
- "micro", and the "C" is for "controller". uClibc was originaly created to
- support uClinux, a port of Linux for MMU-less microcontrollers such as the
- Dragonball, Coldfire, and ARM7TDMI.
-
-
-
-Q: Can I use it on my desktop x86 system?
-
- 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 on your target system.
-
-
-
-Q: Why are you doing this? Whats wrong with glibc?
-
- The inital reason, is that glibc does not support MMU-les systems. But
- additionaly, 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
-
-
-Q: So uClibc is smaller then glibc? Doesn't that mean it completely sucks?
- How could it be smaller and not suck?
-
- 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 make a
- few shotcuts. 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 adds almost 100k to glibc, and yet I am not aware of even
- one Linux application that uses wordexp. So uClibc doesn't have wordexp().
-
- Glibc is a general purpose C library, and so as policy things are optimized
- for speed. uClibc has a large number of routines that have been very
- carefuly written to optimize for size instead of speed.
-
- The end result is a C library that will compile just about everything you
- throw at it, thet looks like glibc to application programs when you
- compile, and is many times smaller.
-
-
-
-Q: Why should I use uClibc?
-
- I don't know if you should use uClibc or not. It depends on your goals.
- 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...
-
-
-
-
-Q: 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 my source code?
-
- No, you do not need to give away your source code just because you use
- uClibc and/or run on Linux.
-
-
-
-Q: I want to create a closed source commercial application using uClibc.
- Is that legal?
-
- 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.
-
-
-
-Q: How do I compile stuff?
-
- 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.
-
-
-
-Q: How do I make autoconf and automake behave?
- First run
- export PATH=/usr/i386-linux-uclibc/bin:$PATH
- (or similar adjusted for your target architecture) then run you can simply
- run autoconf/automake and it should _just work_.
-
-
-
-Q: 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?
-
- 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.
-
-
-
-Q: 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
- Right Now!
-
-
- You have not paid me a single cent and yet you still have the product of
- over year and a half of my work, and lots of work from other people. How
- dare you treat me that way! I work on uClibc because I find it
- interesting. If you go off flaming me, I will ignore you.
-
-
-
-Q: 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?
-
-
- 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
-
-
-Q: I think you guys are great and I want to help support your work!
-
- Wow, that would be great! You can visit
- http://paypal.com/
- click on "Send Money" and donate to andersen@codepoet.org
-
-
-
-I hope that was helpful... If you have and comment, corrections, insults,
-suggestions, or bribes, email me at andersen@codepoet.org.
-
- -Erik
-
---
-Erik B. Andersen
-andersen@codepoet.org
-http://codepoet-consulting.com/