busybox

History

Denys Vlasenko 3b4d04b77e ash: input: Allow two consecutive calls to pungetc Upstream commit: input: Allow two consecutive calls to pungetc The commit ef91d3d6a4c39421fd3a391e02cd82f9f3aee4a8 ([PARSER] Handle backslash newlines properly after dollar sign) created cases where we make two consecutive calls to pungetc. As we don't explicitly support that there are corner cases where you end up with garbage input leading to undefined behaviour. This patch adds explicit support for two consecutive calls to pungetc. Reported-by: Jilles Tjoelker <jilles@stack.nl> Reported-by: Juergen Daubert <jue@jue.li> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> In bbox case, bashism >& may need two pungetc() too. function old new delta pgetc 514 555 +41 pushstring 114 144 +30 basepf 52 76 +24 popstring 134 151 +17 parse_command 1584 1585 +1 pungetc 12 9 -3 ------------------------------------------------------------------------------ (add/remove: 0/0 grow/shrink: 5/1 up/down: 113/-3) Total: 110 bytes Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>		2016-09-29 02:11:19 +02:00
..
ash_test
hush_test
msh_test
ash_doc.txt
ash_ptr_hack.c
ash.c	ash: input: Allow two consecutive calls to pungetc	2016-09-29 02:11:19 +02:00
brace.txt
Config.src
cttyhack.c
hush_doc.txt
hush_leaktool.sh
hush.c
Kbuild.src
match.c
match.h
math.c
math.h
random.c
random.h
README
README.job
shell_common.c
shell_common.h

README

http://www.opengroup.org/onlinepubs/9699919799/
Open Group Base Specifications Issue 7


http://www.opengroup.org/onlinepubs/9699919799/utilities/V3_chap01.html
Shell & Utilities

It says that any of the standard utilities may be implemented
as a regular shell built-in. It gives a list of utilities which
are usually implemented that way (and some of them can only
be implemented as built-ins, like "alias"):

alias
bg
cd
command
false
fc
fg
getopts
jobs
kill
newgrp
pwd
read
true
umask
unalias
wait


http://www.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html
Shell Command Language

It says that shell must implement special built-ins. Special built-ins
differ from regular ones by the fact that variable assignments
done on special builtin are *PRESERVED*. That is,

VAR=VAL special_builtin; echo $VAR

should print VAL.

(Another distinction is that an error in special built-in should
abort the shell, but this is not such a critical difference,
and moreover, at least bash's "set" does not follow this rule,
which is even codified in autoconf configure logic now...)

List of special builtins:

. file
: [argument...]
break [n]
continue [n]
eval [argument...]
exec [command [argument...]]
exit [n]
export name[=word]...
export -p
readonly name[=word]...
readonly -p
return [n]
set [-abCefhmnuvx] [-o option] [argument...]
set [+abCefhmnuvx] [+o option] [argument...]
set -- [argument...]
set -o
set +o
shift [n]
times
trap n [condition...]
trap [action condition...]
unset [-fv] name...

In practice, no one uses this obscure feature - none of these builtins
gives any special reasons to play such dirty tricks.

However. This section also says that *function invocation* should act
similar to special built-in. That is, variable assignments
done on function invocation should be preserved after function invocation.

This is significant: it is not unthinkable to want to run a function
with some variables set to special values. But because of the above,
it does not work: variable will "leak" out of the function.