busybox/shell
Denys Vlasenko 3f4847b6d9 ash: shell: Fix clang warnings about "string plus integer"
Upstream commit:

    Date: Sat, 15 Dec 2018 18:49:31 +0100
    shell: Fix clang warnings about "string plus integer"

    Building with clang results in some warnings about integer values being
    added to strings.

    While the code itself is fine and the warnings are indeed harmless,
    fixing them also makes the semantic more explicit: what it is actually
    being increased is the address which points to the start of the string
    in order to skip the initial character when some conditions are met.

    Signed-off-by: Antonio Ospite <ao2@ao2.it>
    Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2020-02-16 19:29:31 +01:00
..
ash_test ash: [BUILTIN] Exit without arguments in a trap should use status outside traps 2020-02-16 19:14:45 +01:00
hush_test hush: restore redirected stdin 2019-11-01 14:16:07 +01:00
ash_doc.txt
ash_ptr_hack.c
ash.c ash: shell: Fix clang warnings about "string plus integer" 2020-02-16 19:29:31 +01:00
brace.txt
Config.src shell: implement optional "BASE#nnnn" numeric literals 2019-05-19 17:23:31 +02:00
cttyhack.c config: update size information 2018-12-28 03:20:17 +01:00
hush_doc.txt
hush_leaktool.sh
hush.c ash,hush: allow builtins to be tab-completed, closes 7532 2020-01-29 15:23:17 +01:00
Kbuild.src Make it possible to select "sh" and "bash" aliases without selecting ash or hush 2016-12-23 16:56:43 +01:00
match.c hush: fix a='a\\'; echo "${a%\\\\}" 2018-03-02 20:48:36 +01:00
match.h hush: optimize #[#] and %[%] for speed. size -2 bytes. 2010-09-04 21:21:07 +02:00
math.c shell: better comments in BASE#nn code 2019-10-22 14:25:43 +02:00
math.h shell: move all definitions of strto_arith_t() together 2019-05-26 14:02:10 +02:00
random.c whitespace fixes 2018-07-17 15:04:17 +02:00
random.h ash,hush: improve randomness of $RANDOM, add easy-ish way to test it 2014-03-13 12:52:43 +01:00
README
README.job
shell_common.c shell/ulimit: code shrink 2019-10-21 16:47:09 +02:00
shell_common.h hush: fix "export PS1=xyz" and "local PS1=xyz" messing up prompt 2019-05-14 18:56:04 +02:00

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.