+
+Architectural issues:
+
+Do a SUSv3 audit
+ Look at the full Single Unix Specification version 3 (available online at
+ "http://www.opengroup.org/onlinepubs/009695399/nfindex.html") and
+ figure out which of our apps are compliant, and what we're missing that
+ we might actually care about.
+
+ Even better would be some kind of automated compliance test harness that
+ exercises each command line option and the various corner cases.
+--
+Unify archivers
+ Lots of archivers have the same general infrastructure. The directory
+ traversal code should be factored out, and the guts of each archiver could
+ be some setup code and a series of callbacks for "add this file",
+ "add this directory", "add this symlink" and so on.
+
+ This could clean up tar and zip, and make it cheaper to add cpio and ar
+ write support, and possibly even cheaply add things like mkisofs someday,
+ if it becomes relevant.
+---
+Text buffer support.
+ Several existing applets and potential additions (sort, vi, less...) read
+ a whole file into memory and act on it. There might be an opportunity
+ for shared code in there that could be moved into libbb...
+---
+Individual compilation of applets.
+ It would be nice if busybox had the option to compile to individual applets,
+ for people who want an alternate implementation less bloated than the gnu
+ utils (or simply with less political baggage), but without it being one big
+ executable.
+
+ Turning libbb into a real dll is another possibility, especially if libbb
+ could export some of the other library interfaces we've already more or less
+ got the code for (like zlib).
+---
+buildroot - Make a "dogfood" option
+ Busybox is now capable of replacing most gnu packages for real world use,
+ such as developing software or in a live CD. A system built from busybox
+ (1.00 with updated sort.c), uclibc 0.9.27, gcc, binutils, make, and a few
+ other development tools (http://www.landley.net/code/firmware has an example
+ system using autoconf, automake, bison, flex, libtools, m4, zlib,
+ and groff: dunno what subset of that is actually necessary) is capable of
+ rebuilding itself, from scratch, under itself.
+
+ It would be a good "eating our own dogfood" test if buildroot had the option
+ of using busybox instead of bzip2, coreutils, file, findutils, gawk, grep,
+ inetutils, modutils, net-tools, procps, sed, shadow, sysklogd, sysvinit, tar,
+ util-linux, and vim. Anything that's wrong with the resulting system, we
+ can fix. (It would be nice to be able to upgrade busybox to be able to
+ replace bash, diffutils, gzip, less, and patch as well.)
+---
+Memory Allocation
+ We have a CONFIG_BUFFER mechanism that lets us select whether to do memory
+ allocation on the stack or the heap. Unfortunately, we're not using it much.
+ We need to audit our memory allocations and turn a lot of malloc/free calls
+ into RESERVE_CONFIG_BUFFER/RELEASE_CONFIG_BUFFER.
+
+ And while we're at it, many of the CONFIG_FEATURE_CLEAN_UP #ifdefs will be
+ optimized out by the compiler in the stack allocation case (since there's no
+ free for an alloca()), and this means that various cleanup loops that just
+ call free might also be optimized out by the compiler if written right, so
+ we can yank those #ifdefs too, and generally clean up the code.
+---
+Switch CONFIG_SYMBOLS to ENABLE_SYMBOLS
+
+ In busybox 1.0 and earlier, configuration was done by CONFIG_SYMBOLS
+ that were either defined or undefined to indicate whether the symbol was
+ selected in the .config file. They were used with #ifdefs, ala:
+
+ #ifdef CONFIG_SYMBOL
+ if (other_test) {
+ do_code();
+ }
+ #endif
+
+ In 1.1, we have new ENABLE_SYMBOLS which are always defined (as 0 or 1),
+ meaning you can still use them for preprocessor tests by replacing
+ "#ifdef CONFIG_SYMBOL" with "#if ENABLE_SYMBOL". But more importantly, we
+ can use them as a true or false test in normal C code:
+
+ if (ENABLE_SYMBOL && other_test) {
+ do_code();
+ }
+
+ (Optimizing away if() statements that resolve to a constant value
+ is known as "dead code elimination", an optimization so old and simple that
+ Turbo Pascal for DOS did it twenty years ago. Even modern mini-compilers
+ like the Tiny C Compiler (tcc) and the Small Device C Compiler (SDCC)
+ perform dead code elimination.)
+
+ Right now, busybox.h is #including both "config.h" (defining the
+ CONFIG_SYMBOLS) and "bb_config.h" (defining the ENABLE_SYMBOLS). At some
+ point in the future, it would be nice to wean ourselves off of the
+ CONFIG versions. (Among other things, some defective build environments
+ leak the Linux kernel's CONFIG_SYMBOLS into the system's standard #include
+ files. We've experienced collisions before.)
+---
+FEATURE_CLEAN_UP
+ This is more an unresolved issue than a to-do item. More thought is needed.
+
+ Normally we rely on exit() to free memory, close files, and unmap segments
+ for us. This makes most calls to free(), close(), and unmap() optional in
+ busybox applets that don't intend to run for very long, and optional stuff
+ can be omitted to save size.
+
+ The idea was raised that we could simulate fork/exit with setjmp/longjmp
+ for _really_ brainless embedded systems, or speed up the standalone shell
+ by not forking. Doing so would require a reliable FEATURE_CLEAN_UP.
+ Unfortunately, this isn't as easy as it sounds.
+
+ The problem is, lots of things exit(), sometimes unexpectedly (xmalloc())
+ and sometimes reliably (bb_perror_msg_and_die() or show_usage()). This
+ jumps out of the normal flow control and bypasses any cleanup code we
+ put at the end of our applets.
+
+ It's possible to add hooks to libbb functions like xmalloc() and bb_xopen()
+ to add their entries to a linked list, which could be traversed and
+ freed/closed automatically. (This would need to be able to free just the
+ entries after a checkpoint to be usable for a forkless standalone shell.
+ You don't want to free the shell's own resources.)
+
+ Right now, FEATURE_CLEAN_UP is more or less a debugging aid, to make things
+ like valgrind happy. It's also documentation of _what_ we're trusting
+ exit() to clean up for us. But new infrastructure to auto-free stuff would
+ render the existing FEATURE_CLEAN_UP code redundant.
+
+ For right now, exit() handles it just fine.