88e15703ac
Upstreams commit:
Date: Mon, 8 Oct 2007 21:32:25 +0800
[PARSER] Report substition errors at expansion time
On Wed, Apr 11, 2007 at 01:24:21PM -0700, Micah Cowan wrote:
> This operation fails on Ubuntu:
>
> $ /bin/sh -c 'if false; then d="${foo/bar}"; fi'
> /bin/sh: Syntax error: Bad substitution
>
> When used with other POSIX shells it succeeds. While semantically the
> variable reference ${foo/bar} is not valid, this is not a syntax error
> according to POSIX, and since the variable assignment expression is
> never invoked (because it's within an "if false") it should not be seen
> as an error.
>
> I ran into this because after restarting my system I could no longer log
> in. It turns out that the problem was (a) I had edited .gnomerc to
> source my .bashrc file so that my environment would be set properly, and
> (b) I had added some new code to my .bashrc WITHIN A CHECK FOR BASH!
> that used bash's ${var/match/sub} feature. Even though this code was
> within a "case $BASH_VERSION; in *[0-9]*) ... esac (so dash would never
> execute it since that variable is not set), it still caused dash to
> throw up.
>
> FYI, some relevant details from POSIX:
>
> Section 2.3, Token Recognition:
>
> 5. If the current character is an unquoted '$' or '`', the shell shall
> identify the start of any candidates for parameter expansion ( Parameter
> Expansion), command substitution ( Command Substitution), or arithmetic
> expansion ( Arithmetic Expansion) from their introductory unquoted
> character sequences: '$' or "${", "$(" or '`', and "$((", respectively.
> The shell shall read sufficient input to determine the end of the unit
> to be expanded (as explained in the cited sections).
>
> Section 2.6.2, Parameter Expansion:
>
> The format for parameter expansion is as follows:
>
> ${expression}
>
> where expression consists of all characters until the matching '}'. Any
> '}' escaped by a backslash or within a quoted string, and characters in
> embedded arithmetic expansions, command substitutions, and variable
> expansions, shall not be examined in determining the matching '}'.
> [...]
>
> The parameter name or symbol can be enclosed in braces, which are
> optional except for positional parameters with more than one digit or
> when parameter is followed by a character that could be interpreted as
> part of the name. The matching closing brace shall be determined by
> counting brace levels, skipping over enclosed quoted strings, and
> command substitutions.
> ---
> In addition to bash I've checked Solaris /bin/sh and ksh and they don't
> report an error.
>
> -----
> Micah Cowan:
>
> The applicable portion of POSIX is in XCU 2.10.1:
>
> "The WORD tokens shall have the word expansion rules applied to them
> immediately before the associated command is executed, not at the time
> the command is parsed."
>
> This seems fairly clear to me.
This patch moves the error detection to expansion time.
Test case:
if false; then
echo ${a!7}
fi
echo OK
Old result:
dash: Syntax error: Bad substitution
New result:
OK
function old new delta
evalvar 574 585 +11
readtoken1 2763 2750 -13
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
|
||
|---|---|---|
| .. | ||
| ash_test | ||
| hush_test | ||
| ash_doc.txt | ||
| ash_ptr_hack.c | ||
| 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.