Annotation of /trunk/mkinitrd-magellan/busybox/TODO

Busybox TODO

Stuff that needs to be done.  This is organized by who plans to get around to
doing it eventually, but that doesn't mean they "own" the item.  If you want to
do one of these bounce an email off the person it's listed under to see if they
have any suggestions how they plan to go about it, and to minimize conflicts
between your work and theirs.  But otherwise, all of these are fair game.

Rob Landley <rob@landley.net>:
  Add BB_NOMMU to platform.h and migrate __uClinux__ tests to that.
    #if defined __UCLIBC__ && !defined __ARCH_USE_MMU__
  Add a libbb/platform.c
    Implement fdprintf() for platforms that haven't got one.
    Implement bb_realpath() that can handle NULL on non-glibc.
    Cleanup bb_asprintf()

  Migrate calloc() and bb_calloc() occurrences to bb_xzalloc().
  Remove obsolete _() wrapper crud for internationalization we don't do.
  Figure out where we need utf8 support, and add it.

  sh
    The command shell situation is a big mess.  We have three or four different
    shells that don't really share any code, and the "standalone shell" doesn't
    work all that well (especially not in a chroot environment), due to apps not
    being reentrant.  I'm writing a new shell (bbsh) to unify the various
    shells and configurably add the minimal set of bash features people
    actually use.  The hardest part is it has to configure down as small as
    lash while providing lash's features.  The rest is easy in comparison.
  bzip2
    Compression-side support.
  init
    General cleanup (should use ENABLE_FEATURE_INIT_SYSLOG and ENABLE_FEATURE_INIT_DEBUG).
  depmod
    busybox lacks a way to update module deps when running from firmware without the
    use of the depmod.pl (perl is to bloated for most embedded setups) and or orig
    modutils. The orig depmod is rather pointless to have to add to a firmware image
    in when we already have a insmod/rmmod and friends.
  Unify base64 handling.
    There's base64 encoding and decoding going on in:
      networking/wget.c:base64enc()
      coreutils/uudecode.c:read_base64()
      coreutils/uuencode.c:tbl_base64[]
      networking/httpd.c:decodeBase64()
    And probably elsewhere.  That needs to be unified into libbb functions.
  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.
  Internationalization
    How much internationalization should we do?

    The low hanging fruit is UTF-8 character set support.  We should do this.
    (Vodz pointed out the shell's cmdedit as needing work here.  What else?)

    We also have lots of hardwired english text messages.  Consolidating this
    into some kind of message table not only makes translation easier, but
    also allows us to consolidate redundant (or close) strings.

    We probably don't want to be bloated with locale support.  (Not unless we
    can cleanly export it from our underlying C library without having to
    concern ourselves with it directly.  Perhaps a few specific things like a
    config option for "date" are low hanging fruit here?)

    What level should things happen at?  How much do we care about
    internationalizing the text console when X11 and xterms are so much better
    at it?  (There's some infrastructure here we don't implement: The
    "unicode_start" and "unicode_stop" shell scripts need "vt-is-UTF8" and a
    --unicode option to loadkeys.  That implies a real loadkeys/dumpkeys
    implementation to replace loadkmap/dumpkmap.  Plus messing with console font
    loading.  Is it worth it, or do we just say "use X"?)

  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 1.1 will be capable of replacing most gnu packages for real world
    use, such as developing software or in a live CD.  It needs wider testing.

    Busybox should now be able to replace bzip2, coreutils, e2fsprogs, file,
    findutils, gawk, grep, inetutils, less, modutils, net-tools, patch, procps,
    sed, shadow, sysklogd, sysvinit, tar, util-linux, and vim.  The resulting
    system should be self-hosting (I.E. able to rebuild itself from source
    code).  This means it would need (at least) binutils, gcc, and make, or
    equivalents.

    It would be a good "eating our own dogfood" test if buildroot had the option
    of using a "make allyesconfig" busybox instead of the all of the above
    packages.  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 and
    diffutils as well, but we're not there yet.)

    One example of an existing system that does this already is Firmware Linux:
      http://www.landley.net/code/firmware
  initramfs
    Busybox should have a sample initramfs build script.  This depends on
    bbsh, mdev, and switch_root.
  mkdep
    Write a mkdep that doesn't segfault if there's a directory it doesn't
    have permission to read, isn't based on manually editing the output of
    lexx and yacc, doesn't make such a mess under include/config, etc.
  Group globals into unions of structures.
    Go through and turn all the global and static variables into structures,
    and have all those structures be in a big union shared between processes,
    so busybox uses less bss.  (This is a big win on nommu machines.)  See
    sed.c and mdev.c for examples.
  Go through bugs.busybox.net and close out all of that somehow.
    This one's open to everybody, but I'll wind up doing it...


Bernhard Fischer <busybox@busybox.net> suggests to look at these:
  New debug options:
    -Wlarger-than-127
    Cleanup any big users
    -Wunused-parameter
    Facilitate applet PROTOTYPES to provide means for having applets that
    do a) not take any arguments b) need only one of argc or argv c) need
    both argc and argv. All of these three options should go for the most
    feature complete denominator.
  Collate BUFSIZ IOBUF_SIZE MY_BUF_SIZE PIPE_PROGRESS_SIZE BUFSIZE PIPESIZE
    make bb_common_bufsiz1 configurable, size wise.
    make pipesize configurable, size wise.
    Use bb_common_bufsiz1 throughout applets!
  Add chrt applet. Please CC Bernhard if you suggest a patch.

As yet unclaimed:

----
find
  doesn't understand (), lots of susv3 stuff.
----
diff
  Make sure we handle empty files properly:
    From the patch man page:

    you can remove a file by sending out a context diff that compares
    the file to be deleted with an empty file dated the Epoch.  The
    file will be removed unless patch is conforming to POSIX and the
    -E or --remove-empty-files option is not given.
---
patch
  Should have simple fuzz factor support to apply patches at an offset which
  shouldn't take up too much space.

  And while we're at it, a new patch filename quoting format is apparently
  coming soon:  http://marc.theaimsgroup.com/?l=git&m=112927316408690&w=2
---
man
  It would be nice to have a man command.  Not one that handles troff or
  anything, just one that can handle preformatted ascii man pages, possibly
  compressed.  This could probably be a script in the extras directory that
  calls cat/zcat/bzcat | less

  (How doclifter might work into this is anybody's guess.)
---
ar
  Write support?
----
stty / catv
  stty's visible() function and catv's guts are identical. Merge them into
  an appropriate libbb function.
----

Architectural issues:

bb_close() with fsync()
  We should have a bb_close() in place of normal close, with a CONFIG_ option
  to not just check the return value of close() for an error, but fsync().
  Close can't reliably report anything useful because if write() accepted the
  data then it either went out to the network or it's in cache or a pipe
  buffer.  Either way, there's no guarantee it'll make it to its final
  destination before close() gets called, so there's no guarantee that any
  error will be reported.

  You need to call fsync() if you care about errors that occur after write(),
  but that can have a big performance impact.  So make it a config option.
---
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 or
  mksquashfs someday, if they become relevant.
---
Text buffer support.
  Several existing applets (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...
---
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.
  For a start, see e.g. make EXTRA_CFLAGS=-Wlarger-than-64

  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 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.


Minor stuff:
  watchdog.c could autodetect the timer duration via:
    if(!ioctl (fd, WDIOC_GETTIMEOUT, &tmo)) timer_duration = 1 + (tmo / 2);
  Unfortunately, that needs linux/watchdog.h and that contains unfiltered
  kernel types on some distros, which breaks the build.
---
  use bb_error_msg where appropriate: See
  egrep "(printf.*\([[:space:]]*(stderr|2)|[^_]write.*\([[:space:]]*(stderr|2))"
---
  use bb_perror_msg where appropriate: See
  egrep "[^_]perror"
---
  Remove superfluous fmt occurances: e.g.
  fprintf(stderr, "%s: %s not found\n", "unalias", *argptr);
  -> fprintf(stderr, "unalias: %s not found\n", *argptr);
---
  possible code duplication ingroup() and is_a_group_member()
---
  Move __get_hz() to a better place and (re)use it in route.c, ash.c, msh.c
---


Code cleanup:

Replace deprecated functions.

bzero() -> memset()
---
sigblock(), siggetmask(), sigsetmask(), sigmask() -> sigprocmask et al
---
vdprintf() -> similar sized functionality
---
1	niro	532	Busybox TODO
2
3			Stuff that needs to be done. This is organized by who plans to get around to
4			doing it eventually, but that doesn't mean they "own" the item. If you want to
5			do one of these bounce an email off the person it's listed under to see if they
6			have any suggestions how they plan to go about it, and to minimize conflicts
7			between your work and theirs. But otherwise, all of these are fair game.
8
9			Rob Landley <rob@landley.net>:
10			Add BB_NOMMU to platform.h and migrate __uClinux__ tests to that.
11			#if defined __UCLIBC__ && !defined __ARCH_USE_MMU__
12			Add a libbb/platform.c
13			Implement fdprintf() for platforms that haven't got one.
14			Implement bb_realpath() that can handle NULL on non-glibc.
15			Cleanup bb_asprintf()
16
17			Migrate calloc() and bb_calloc() occurrences to bb_xzalloc().
18			Remove obsolete _() wrapper crud for internationalization we don't do.
19			Figure out where we need utf8 support, and add it.
20
21			sh
22			The command shell situation is a big mess. We have three or four different
23			shells that don't really share any code, and the "standalone shell" doesn't
24			work all that well (especially not in a chroot environment), due to apps not
25			being reentrant. I'm writing a new shell (bbsh) to unify the various
26			shells and configurably add the minimal set of bash features people
27			actually use. The hardest part is it has to configure down as small as
28			lash while providing lash's features. The rest is easy in comparison.
29			bzip2
30			Compression-side support.
31			init
32			General cleanup (should use ENABLE_FEATURE_INIT_SYSLOG and ENABLE_FEATURE_INIT_DEBUG).
33			depmod
34			busybox lacks a way to update module deps when running from firmware without the
35			use of the depmod.pl (perl is to bloated for most embedded setups) and or orig
36			modutils. The orig depmod is rather pointless to have to add to a firmware image
37			in when we already have a insmod/rmmod and friends.
38			Unify base64 handling.
39			There's base64 encoding and decoding going on in:
40			networking/wget.c:base64enc()
41			coreutils/uudecode.c:read_base64()
42			coreutils/uuencode.c:tbl_base64[]
43			networking/httpd.c:decodeBase64()
44			And probably elsewhere. That needs to be unified into libbb functions.
45			Do a SUSv3 audit
46			Look at the full Single Unix Specification version 3 (available online at
47			"http://www.opengroup.org/onlinepubs/009695399/nfindex.html") and
48			figure out which of our apps are compliant, and what we're missing that
49			we might actually care about.
50
51			Even better would be some kind of automated compliance test harness that
52			exercises each command line option and the various corner cases.
53			Internationalization
54			How much internationalization should we do?
55
56			The low hanging fruit is UTF-8 character set support. We should do this.
57			(Vodz pointed out the shell's cmdedit as needing work here. What else?)
58
59			We also have lots of hardwired english text messages. Consolidating this
60			into some kind of message table not only makes translation easier, but
61			also allows us to consolidate redundant (or close) strings.
62
63			We probably don't want to be bloated with locale support. (Not unless we
64			can cleanly export it from our underlying C library without having to
65			concern ourselves with it directly. Perhaps a few specific things like a
66			config option for "date" are low hanging fruit here?)
67
68			What level should things happen at? How much do we care about
69			internationalizing the text console when X11 and xterms are so much better
70			at it? (There's some infrastructure here we don't implement: The
71			"unicode_start" and "unicode_stop" shell scripts need "vt-is-UTF8" and a
72			--unicode option to loadkeys. That implies a real loadkeys/dumpkeys
73			implementation to replace loadkmap/dumpkmap. Plus messing with console font
74			loading. Is it worth it, or do we just say "use X"?)
75
76			Individual compilation of applets.
77			It would be nice if busybox had the option to compile to individual applets,
78			for people who want an alternate implementation less bloated than the gnu
79			utils (or simply with less political baggage), but without it being one big
80			executable.
81
82			Turning libbb into a real dll is another possibility, especially if libbb
83			could export some of the other library interfaces we've already more or less
84			got the code for (like zlib).
85			buildroot - Make a "dogfood" option
86			Busybox 1.1 will be capable of replacing most gnu packages for real world
87			use, such as developing software or in a live CD. It needs wider testing.
88
89			Busybox should now be able to replace bzip2, coreutils, e2fsprogs, file,
90			findutils, gawk, grep, inetutils, less, modutils, net-tools, patch, procps,
91			sed, shadow, sysklogd, sysvinit, tar, util-linux, and vim. The resulting
92			system should be self-hosting (I.E. able to rebuild itself from source
93			code). This means it would need (at least) binutils, gcc, and make, or
94			equivalents.
95
96			It would be a good "eating our own dogfood" test if buildroot had the option
97			of using a "make allyesconfig" busybox instead of the all of the above
98			packages. Anything that's wrong with the resulting system, we can fix. (It
99			would be nice to be able to upgrade busybox to be able to replace bash and
100			diffutils as well, but we're not there yet.)
101
102			One example of an existing system that does this already is Firmware Linux:
103			http://www.landley.net/code/firmware
104			initramfs
105			Busybox should have a sample initramfs build script. This depends on
106			bbsh, mdev, and switch_root.
107			mkdep
108			Write a mkdep that doesn't segfault if there's a directory it doesn't
109			have permission to read, isn't based on manually editing the output of
110			lexx and yacc, doesn't make such a mess under include/config, etc.
111			Group globals into unions of structures.
112			Go through and turn all the global and static variables into structures,
113			and have all those structures be in a big union shared between processes,
114			so busybox uses less bss. (This is a big win on nommu machines.) See
115			sed.c and mdev.c for examples.
116			Go through bugs.busybox.net and close out all of that somehow.
117			This one's open to everybody, but I'll wind up doing it...
118
119
120			Bernhard Fischer <busybox@busybox.net> suggests to look at these:
121			New debug options:
122			-Wlarger-than-127
123			Cleanup any big users
124			-Wunused-parameter
125			Facilitate applet PROTOTYPES to provide means for having applets that
126			do a) not take any arguments b) need only one of argc or argv c) need
127			both argc and argv. All of these three options should go for the most
128			feature complete denominator.
129			Collate BUFSIZ IOBUF_SIZE MY_BUF_SIZE PIPE_PROGRESS_SIZE BUFSIZE PIPESIZE
130			make bb_common_bufsiz1 configurable, size wise.
131			make pipesize configurable, size wise.
132			Use bb_common_bufsiz1 throughout applets!
133			Add chrt applet. Please CC Bernhard if you suggest a patch.
134
135			As yet unclaimed:
136
137			----
138			find
139			doesn't understand (), lots of susv3 stuff.
140			----
141			diff
142			Make sure we handle empty files properly:
143			From the patch man page:
144
145			you can remove a file by sending out a context diff that compares
146			the file to be deleted with an empty file dated the Epoch. The
147			file will be removed unless patch is conforming to POSIX and the
148			-E or --remove-empty-files option is not given.
149			---
150			patch
151			Should have simple fuzz factor support to apply patches at an offset which
152			shouldn't take up too much space.
153
154			And while we're at it, a new patch filename quoting format is apparently
155			coming soon: http://marc.theaimsgroup.com/?l=git&m=112927316408690&w=2
156			---
157			man
158			It would be nice to have a man command. Not one that handles troff or
159			anything, just one that can handle preformatted ascii man pages, possibly
160			compressed. This could probably be a script in the extras directory that
161			calls cat/zcat/bzcat \| less
162
163			(How doclifter might work into this is anybody's guess.)
164			---
165			ar
166			Write support?
167			----
168			stty / catv
169			stty's visible() function and catv's guts are identical. Merge them into
170			an appropriate libbb function.
171			----
172
173			Architectural issues:
174
175			bb_close() with fsync()
176			We should have a bb_close() in place of normal close, with a CONFIG_ option
177			to not just check the return value of close() for an error, but fsync().
178			Close can't reliably report anything useful because if write() accepted the
179			data then it either went out to the network or it's in cache or a pipe
180			buffer. Either way, there's no guarantee it'll make it to its final
181			destination before close() gets called, so there's no guarantee that any
182			error will be reported.
183
184			You need to call fsync() if you care about errors that occur after write(),
185			but that can have a big performance impact. So make it a config option.
186			---
187			Unify archivers
188			Lots of archivers have the same general infrastructure. The directory
189			traversal code should be factored out, and the guts of each archiver could
190			be some setup code and a series of callbacks for "add this file",
191			"add this directory", "add this symlink" and so on.
192
193			This could clean up tar and zip, and make it cheaper to add cpio and ar
194			write support, and possibly even cheaply add things like mkisofs or
195			mksquashfs someday, if they become relevant.
196			---
197			Text buffer support.
198			Several existing applets (sort, vi, less...) read
199			a whole file into memory and act on it. There might be an opportunity
200			for shared code in there that could be moved into libbb...
201			---
202			Memory Allocation
203			We have a CONFIG_BUFFER mechanism that lets us select whether to do memory
204			allocation on the stack or the heap. Unfortunately, we're not using it much.
205			We need to audit our memory allocations and turn a lot of malloc/free calls
206			into RESERVE_CONFIG_BUFFER/RELEASE_CONFIG_BUFFER.
207			For a start, see e.g. make EXTRA_CFLAGS=-Wlarger-than-64
208
209			And while we're at it, many of the CONFIG_FEATURE_CLEAN_UP #ifdefs will be
210			optimized out by the compiler in the stack allocation case (since there's no
211			free for an alloca()), and this means that various cleanup loops that just
212			call free might also be optimized out by the compiler if written right, so
213			we can yank those #ifdefs too, and generally clean up the code.
214			---
215			Switch CONFIG_SYMBOLS to ENABLE_SYMBOLS
216
217			In busybox 1.0 and earlier, configuration was done by CONFIG_SYMBOLS
218			that were either defined or undefined to indicate whether the symbol was
219			selected in the .config file. They were used with #ifdefs, ala:
220
221			#ifdef CONFIG_SYMBOL
222			if (other_test) {
223			do_code();
224			}
225			#endif
226
227			In 1.1, we have new ENABLE_SYMBOLS which are always defined (as 0 or 1),
228			meaning you can still use them for preprocessor tests by replacing
229			"#ifdef CONFIG_SYMBOL" with "#if ENABLE_SYMBOL". But more importantly, we
230			can use them as a true or false test in normal C code:
231
232			if (ENABLE_SYMBOL && other_test) {
233			do_code();
234			}
235
236			(Optimizing away if() statements that resolve to a constant value
237			is known as "dead code elimination", an optimization so old and simple that
238			Turbo Pascal for DOS did it twenty years ago. Even modern mini-compilers
239			like the Tiny C Compiler (tcc) and the Small Device C Compiler (SDCC)
240			perform dead code elimination.)
241
242			Right now, busybox.h is #including both "config.h" (defining the
243			CONFIG_SYMBOLS) and "bb_config.h" (defining the ENABLE_SYMBOLS). At some
244			point in the future, it would be nice to wean ourselves off of the
245			CONFIG versions. (Among other things, some defective build environments
246			leak the Linux kernel's CONFIG_SYMBOLS into the system's standard #include
247			files. We've experienced collisions before.)
248			---
249			FEATURE_CLEAN_UP
250			This is more an unresolved issue than a to-do item. More thought is needed.
251
252			Normally we rely on exit() to free memory, close files, and unmap segments
253			for us. This makes most calls to free(), close(), and unmap() optional in
254			busybox applets that don't intend to run for very long, and optional stuff
255			can be omitted to save size.
256
257			The idea was raised that we could simulate fork/exit with setjmp/longjmp
258			for _really_ brainless embedded systems, or speed up the standalone shell
259			by not forking. Doing so would require a reliable FEATURE_CLEAN_UP.
260			Unfortunately, this isn't as easy as it sounds.
261
262			The problem is, lots of things exit(), sometimes unexpectedly (xmalloc())
263			and sometimes reliably (bb_perror_msg_and_die() or show_usage()). This
264			jumps out of the normal flow control and bypasses any cleanup code we
265			put at the end of our applets.
266
267			It's possible to add hooks to libbb functions like xmalloc() and xopen()
268			to add their entries to a linked list, which could be traversed and
269			freed/closed automatically. (This would need to be able to free just the
270			entries after a checkpoint to be usable for a forkless standalone shell.
271			You don't want to free the shell's own resources.)
272
273			Right now, FEATURE_CLEAN_UP is more or less a debugging aid, to make things
274			like valgrind happy. It's also documentation of _what_ we're trusting
275			exit() to clean up for us. But new infrastructure to auto-free stuff would
276			render the existing FEATURE_CLEAN_UP code redundant.
277
278			For right now, exit() handles it just fine.
279
280
281
282			Minor stuff:
283			watchdog.c could autodetect the timer duration via:
284			if(!ioctl (fd, WDIOC_GETTIMEOUT, &tmo)) timer_duration = 1 + (tmo / 2);
285			Unfortunately, that needs linux/watchdog.h and that contains unfiltered
286			kernel types on some distros, which breaks the build.
287			---
288			use bb_error_msg where appropriate: See
289			egrep "(printf.\([[:space:]](stderr\|2)\|[^_]write.\([[:space:]](stderr\|2))"
290			---
291			use bb_perror_msg where appropriate: See
292			egrep "[^_]perror"
293			---
294			Remove superfluous fmt occurances: e.g.
295			fprintf(stderr, "%s: %s not found\n", "unalias", *argptr);
296			-> fprintf(stderr, "unalias: %s not found\n", *argptr);
297			---
298			possible code duplication ingroup() and is_a_group_member()
299			---
300			Move __get_hz() to a better place and (re)use it in route.c, ash.c, msh.c
301			---
302
303
304			Code cleanup:
305
306			Replace deprecated functions.
307
308			bzero() -> memset()
309			---
310			sigblock(), siggetmask(), sigsetmask(), sigmask() -> sigprocmask et al
311			---
312			vdprintf() -> similar sized functionality
313			---