Re: FYI: fix dollar handling in func_quote_for_expand [libtool--devo--1.0--patch-265]

[Noah Misch]

On Wed, Oct 20, 2004 at 09:45:46PM +0100, Gary V. Vaughan wrote:

>       (func_quote_for_eval): Four space indent margin for functions!

Does this deserve mention in HACKING?

>   +# Save mangling of backslash escaped dollars by the above.  Running this
>   +# substitution after double_quote_subst notices and corrects expansion
>   +# of already escaped meta-chars.  \$x -> double_quote_subst -> \\$x,
>   +# which doesn't protect $x from expansion.  To correct this we do:
>   +# \\$x -> sed_double_backslash -> \\\$x, properly protecting $x.
>   +sed_double_backslash='s/\([[^\\]]\)\\\\$/\1\\\\\\$/g'

I am glad you caught that.  The first $ does need a \, and I believe the \ in
the character class does not need one.  That said, this substitution handles
'x\$y', but it does not seem to handle '\$y' (no non-backslash preceding
character) or 'x\\\$y'.  I believe this variant does so:

# Re-`\' parameter expansions in output of double_quote_subst that were
# `\'-ed in input to the same.  If an odd number of `\' preceded a '$'
# in input to double_quote_subst, that '$' was protected from expansion.
# Since each input `\' is now two `\'s, look for any number of runs of
# four `\'s followed by two `\'s and then a '$'.  `\' that '$'.  Note
# that the embedded single quotes serve only to enhance readability.
sed_double_backslash='s/\(\(^\|[^\]\)\(\\\\''\\\\''\)*\)''\\\\''\$/\1\\\\''\\''\$/g'

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