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authorDenys Vlasenko <vda.linux@googlemail.com>2016-10-26 01:55:56 +0200
committerDenys Vlasenko <vda.linux@googlemail.com>2016-10-26 01:55:56 +0200
commit88e15703acdbfb182440cf35fdb8972fc4931dd2 (patch)
treeabdeba10ffe2446c197bdb2d539fb1c4f3fb5277 /include/busybox.h
parenteaf9436b08f68be8b96730307fe1da1faf374ee0 (diff)
downloadbusybox-88e15703acdbfb182440cf35fdb8972fc4931dd2.tar.gz
ash: [PARSER] Report substition errors at expansion time
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>
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