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205 lines
9.3 KiB
Plaintext
205 lines
9.3 KiB
Plaintext
Busybox TODO
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Stuff that needs to be done
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find
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doesn't understand (), lots of susv3 stuff.
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----
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sh
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The command shell situation is a big mess. We have three or four different
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shells that don't really share any code, and the "standalone shell" doesn't
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work all that well (especially not in a chroot environment), due to apps not
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being reentrant. Unifying the various shells and figuring out a configurable
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way of adding the minimal set of bash features a given script uses is a big
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job, but it would be a big improvement.
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Note: Rob Landley (rob@landley.net) is working on this one, but very slowly...
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---
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diff
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We should have a diff -u command. We have patch, we should have diff
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(we only need to support unified diffs though).
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---
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patch
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Should have simple fuzz factor support to apply patches at an offset which
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shouldn't take up too much space.
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And while we're at it, a new patch filename quoting format is apparently
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coming soon: http://marc.theaimsgroup.com/?l=git&m=112927316408690&w=2
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---
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man
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It would be nice to have a man command. Not one that handles troff or
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anything, just one that can handle preformatted ascii man pages, possibly
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compressed. This could probably be a script in the extras directory that
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calls cat/zcat/bzcat | less
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---
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bzip2
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Compression-side support.
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---
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init
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General cleanup.
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Architectural issues:
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bb_close() with fsync()
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We should have a bb_close() in place of normal close, with a CONFIG_ option
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to not just check the return value of close() for an error, but fsync().
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Close can't reliably report anything useful because if write() accepted the
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data then it either went out or it's in cache or a pipe buffer. Either way,
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there's no guarantee it'll make it to its final destination before close()
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gets called, so there's no guarantee that any error will be reported.
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You need to call fsync() if you care about errors that occur after write(),
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but that can have a big performance impact. So make it a config option.
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---
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Do a SUSv3 audit
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Look at the full Single Unix Specification version 3 (available online at
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"http://www.opengroup.org/onlinepubs/009695399/nfindex.html") and
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figure out which of our apps are compliant, and what we're missing that
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we might actually care about.
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Even better would be some kind of automated compliance test harness that
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exercises each command line option and the various corner cases.
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---
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Internationalization
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How much internationalization should we do?
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The low hanging fruit is UTF-8 character set support. We should do this.
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(Vodz pointed out the shell's cmdedit as needing work here. What else?)
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We also have lots of hardwired english text messages. Consolidating this
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into some kind of message table not only makes translation easier, but
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also allows us to consolidate redundant (or close) strings.
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We probably don't want to be bloated with locale support. (Not unless we can
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cleanly export it from our underlying C library without having to concern
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ourselves with it directly. Perhaps a few specific things like a config
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option for "date" are low hanging fruit here?)
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What level should things happen at? How much do we care about
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internationalizing the text console when X11 and xterms are so much better
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at it? (There's some infrastructure here we don't implement: The
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"unicode_start" and "unicode_stop" shell scripts need "vt-is-UTF8" and a
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--unicode option to loadkeys. That implies a real loadkeys/dumpkeys
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implementation to replace loadkmap/dumpkmap. Plus messing with console font
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loading. Is it worth it, or do we just say "use X"?)
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---
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Unify archivers
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Lots of archivers have the same general infrastructure. The directory
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traversal code should be factored out, and the guts of each archiver could
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be some setup code and a series of callbacks for "add this file",
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"add this directory", "add this symlink" and so on.
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This could clean up tar and zip, and make it cheaper to add cpio and ar
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write support, and possibly even cheaply add things like mkisofs someday,
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if it becomes relevant.
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---
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Text buffer support.
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Several existing applets (sort, vi, less...) read
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a whole file into memory and act on it. There might be an opportunity
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for shared code in there that could be moved into libbb...
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---
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Individual compilation of applets.
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It would be nice if busybox had the option to compile to individual applets,
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for people who want an alternate implementation less bloated than the gnu
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utils (or simply with less political baggage), but without it being one big
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executable.
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Turning libbb into a real dll is another possibility, especially if libbb
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could export some of the other library interfaces we've already more or less
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got the code for (like zlib).
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---
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buildroot - Make a "dogfood" option
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Busybox 1.1 will be capable of replacing most gnu packages for real world use,
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such as developing software or in a live CD. It needs wider testing.
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Busybox should now be able to replace bzip2, coreutils, e2fsprogs, file,
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findutils, gawk, grep, inetutils, less, modutils, net-tools, patch, procps,
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sed, shadow, sysklogd, sysvinit, tar, util-linux, and vim. The resulting
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system should be self-hosting (I.E. able to rebuild itself from source code).
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This means it would need (at least) binutils, gcc, and make, or equivalents.
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It would be a good "eating our own dogfood" test if buildroot had the option
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of using a "make allyesconfig" busybox instead of the all of the above
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packages. Anything that's wrong with the resulting system, we can fix. (It
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would be nice to be able to upgrade busybox to be able to replace bash and
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diffutils as well, but we're not there yet.)
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One example of an existing system that does this already is Firmware Linux:
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http://www.landley.net/code/firmware
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---
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Memory Allocation
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We have a CONFIG_BUFFER mechanism that lets us select whether to do memory
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allocation on the stack or the heap. Unfortunately, we're not using it much.
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We need to audit our memory allocations and turn a lot of malloc/free calls
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into RESERVE_CONFIG_BUFFER/RELEASE_CONFIG_BUFFER.
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And while we're at it, many of the CONFIG_FEATURE_CLEAN_UP #ifdefs will be
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optimized out by the compiler in the stack allocation case (since there's no
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free for an alloca()), and this means that various cleanup loops that just
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call free might also be optimized out by the compiler if written right, so
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we can yank those #ifdefs too, and generally clean up the code.
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---
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Switch CONFIG_SYMBOLS to ENABLE_SYMBOLS
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In busybox 1.0 and earlier, configuration was done by CONFIG_SYMBOLS
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that were either defined or undefined to indicate whether the symbol was
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selected in the .config file. They were used with #ifdefs, ala:
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#ifdef CONFIG_SYMBOL
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if (other_test) {
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do_code();
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}
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#endif
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In 1.1, we have new ENABLE_SYMBOLS which are always defined (as 0 or 1),
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meaning you can still use them for preprocessor tests by replacing
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"#ifdef CONFIG_SYMBOL" with "#if ENABLE_SYMBOL". But more importantly, we
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can use them as a true or false test in normal C code:
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if (ENABLE_SYMBOL && other_test) {
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do_code();
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}
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(Optimizing away if() statements that resolve to a constant value
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is known as "dead code elimination", an optimization so old and simple that
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Turbo Pascal for DOS did it twenty years ago. Even modern mini-compilers
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like the Tiny C Compiler (tcc) and the Small Device C Compiler (SDCC)
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perform dead code elimination.)
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Right now, busybox.h is #including both "config.h" (defining the
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CONFIG_SYMBOLS) and "bb_config.h" (defining the ENABLE_SYMBOLS). At some
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point in the future, it would be nice to wean ourselves off of the
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CONFIG versions. (Among other things, some defective build environments
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leak the Linux kernel's CONFIG_SYMBOLS into the system's standard #include
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files. We've experienced collisions before.)
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---
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FEATURE_CLEAN_UP
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This is more an unresolved issue than a to-do item. More thought is needed.
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Normally we rely on exit() to free memory, close files, and unmap segments
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for us. This makes most calls to free(), close(), and unmap() optional in
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busybox applets that don't intend to run for very long, and optional stuff
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can be omitted to save size.
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The idea was raised that we could simulate fork/exit with setjmp/longjmp
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for _really_ brainless embedded systems, or speed up the standalone shell
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by not forking. Doing so would require a reliable FEATURE_CLEAN_UP.
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Unfortunately, this isn't as easy as it sounds.
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The problem is, lots of things exit(), sometimes unexpectedly (xmalloc())
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and sometimes reliably (bb_perror_msg_and_die() or show_usage()). This
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jumps out of the normal flow control and bypasses any cleanup code we
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put at the end of our applets.
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It's possible to add hooks to libbb functions like xmalloc() and bb_xopen()
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to add their entries to a linked list, which could be traversed and
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freed/closed automatically. (This would need to be able to free just the
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entries after a checkpoint to be usable for a forkless standalone shell.
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You don't want to free the shell's own resources.)
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Right now, FEATURE_CLEAN_UP is more or less a debugging aid, to make things
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like valgrind happy. It's also documentation of _what_ we're trusting
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exit() to clean up for us. But new infrastructure to auto-free stuff would
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render the existing FEATURE_CLEAN_UP code redundant.
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For right now, exit() handles it just fine.
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