48cb983b13
Upstream commit:
Date: Wed, 27 May 2020 12:19:13 +1000
parser: Get rid of PEOA
PEOA is a special character used to mark an alias as being finished
so that we don't enter an infinite loop with nested aliases. It
complicates the parser because we have to ensure that it is skipped
where necessary and not copied to the resulting token text.
This patch removes it and instead delays the marking of aliases
until the second pgetc. This has the same effect as the current
PEOA code while keeping the complexities within the input code.
This adds ~32 bytes of global data:
function old new delta
__pgetc - 512 +512
freestrings - 95 +95
popfile 86 110 +24
pushstring 141 160 +19
basepf 76 84 +8
syntax_index_table 258 257 -1
S_I_T 30 28 -2
.rodata 104255 104247 -8
pgetc_without_PEOA 13 - -13
xxreadtoken 230 215 -15
popstring 158 120 -38
readtoken1 3110 3045 -65
pgetc 547 22 -525
------------------------------------------------------------------------------
(add/remove: 2/1 grow/shrink: 3/7 up/down: 658/-667) Total: -9 bytes
text data bss dec hex filename
1043102 559 5020 1048681 100069 busybox_old
1043085 559 5052 1048696 100078 busybox_unstripped
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
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|---|---|---|
| .. | ||
| ash_test | ||
| hush_test | ||
| ash_doc.txt | ||
| ash_ptr_hack.c | ||
| ash_remove_unnecessary_code_in_backquote_expansion.patch | ||
| ash.c | ||
| 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 | ||
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.