Quotation of patterns is not POSIXly correct
magicant magicant Other examples
ForkP="x\?x"; var='x?xyyy';printf '%s\n' ${var#${P}}
P="x\?x"; var='x?xyyy';printf '%s\n' "${var#${P}}"
P="\[a]"; var='[a]bc';printf '%s\n' ${var#$P}
P="\\[a]"; var='[a]bc';printf '%s\n' ${var#$P}
P="\\?"; var='1-2-3-\?';printf '%s\n' ${var%-${P}}
magicant magicant In word expansion in the simple command, backslashes are correctly handled. So, to fix this bug, we should do the same thing to the case pattern?
$ v='\z' $ printf '%s\n' \z $v z \z
magicant The problem is not that simple.
Currently the expand_four function returns \\z for ${var}, which is indistinguishable from literal \z. We need to tell if the backslash was part of the original word or coming from expansion, since the quote removal rule requires to remove only the former.
Idea: Can we (ab)use the splittability string to tell whether the backslash is subject to quote removal?
magicant XCU 2.6.1:
The pathname resulting from tilde expansion shall be treated as if quoted to prevent it being altered by field splitting and pathname expansion.
XCU 2.6.2:
If a parameter expansion occurs inside double-quotes: ... Field splitting shall not be performed on the results of the expansion.
XCU 2.6.3:
If a command substitution occurs inside double-quotes, field splitting and pathname expansion shall not be performed on the results of the substitution.
XCU 2.6.5:
the shell shall scan the results of expansions and substitutions that did not occur in double-quotes for field splitting and multiple fields can result.
To sum up, field splitting is performed on the results of unquoted expansions (but not tilde expansion).
XCU 2.6.7:
The quote characters ( <backslash>, single-quote, and double-quote) that were present in the original word shall be removed unless they have themselves been quoted.
This is almost the same as "the quote characters resulting from expansions", but including the results from tilde expansion. (sigh)
magicant Yash prints 1-2-3 for IFS=-; echo "${unset-1\-2-3}" but other shells (bash, dash, ksh, mksh, zsh) correctly prints 1\-2-3. Maybe this issue can be handled in this ticket?
Note that all the shells including yash correctly prints 1-2 3 for IFS=-; echo ${unset-1\-2-3} and that the behavior is not well-defined for IFS=-; echo "${unset-"1\-2-3"}".
magicant XCU 2.13.1
If a pattern ends with an unescaped <backslash>, it is unspecified whether the pattern does not match anything or the pattern is treated as invalid.
Ouch. Yash's behavior is neither of the two. I need to fix some tests, too.
But, wait, existing shells (including yash) print match for the following code, which is contrary to POSIX...:
bs='\'
case \\ in ${bs}) echo match; esac
magicant)
magicant magicant The main issue was fixed in r4073
magicant magicant への返信
Yash prints 1-2-3 for IFS=-; echo "${unset-1\-2-3}" but other shells (bash, dash, ksh, mksh, zsh) correctly prints 1\-2-3. Maybe this issue can be handled in this ticket? Note that all the shells including yash correctly prints 1-2 3 for IFS=-; echo ${unset-1\-2-3} and that the behavior is not well-defined for IFS=-; echo "${unset-"1\-2-3"}".
I'll handle this in #40751.
magicant magicant への返信
XCU 2.13.1
If a pattern ends with an unescaped <backslash>, it is unspecified whether the pattern does not match anything or the pattern is treated as invalid.
Ouch. Yash's behavior is neither of the two. I need to fix some tests, too. But, wait, existing shells (including yash) print match for the following code, which is contrary to POSIX...: {{{ bs='\' case \\ in ${bs}) echo match; esac }}}
New ticket: #40752.
magicant
var="\z" case ${var} in (${var}) printf M;; (*) printf X;; esacThis should not match because the backslash in the pattern should be special (an escape character).
Pull request: https://github.com/magicant/yash/pull/8