URL: <https://savannah.gnu.org/support/?111221>
Summary: _AC_DEFINE_UNQUOTED has broken regex
Group: Autoconf
Submitter: ericb
Submitted: Mon 07 Apr 2025 10:48:46 AM CDT
Priority: 5 - Unprioritized
Severity: 3 - Normal
Status: None
Privacy: Public
Assigned to: None
Originator Email:
Open/Closed: Open
Discussion Lock: Any
Operating System: None
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Follow-up Comments:
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Date: Mon 07 Apr 2025 10:48:46 AM CDT By: Eric Blake <ericb>
Captured from https://lists.gnu.org/archive/html/bug-m4/2025-04/msg00027.html.
It looks like the existing regex of _AC_DEFINE_UNQUOTED searches for the
literal 8-byte string "(|{|@S|@" when it really wanted to search for the
alternation of any of the following three strings "(" "{" "@S|@".
lib/autoconf/general.m4:[m4_if(m4_bregexp([$1],
[#\|\\\|`\|\(\$\|@S|@\)\((|{|@{:@\)]), [-1],
in the definition of _AC_DEFINE_UNQUOTED. That regex is asking for a
literal "#", "\", "`", or the concatenation of [either "$" or the
quadrigraph "@S|@" (an alias for "$")] with [literal "(|{|"
concatenated with the quadrigraph @{:@ (for "(")]. Despite my HUH[*]?
factor, this appears to WANT to match a "{" as a literal, at any rate,
since it is using bare "{" with the next byte neither a digit nor ",",
it would break if we turn on "{}" for intervals by default.
[*]At any rate, I think that's a bug in autoconf (hence why I added
them in cc). If the _intent_ was to match literal "#", "\", "`", and
the sequences "$(" and "${" (either as literals or via quadrigraphs),
it isn't quite doing that. The correct spelling (with added
whitespace for clarity, although the whitespace would not be part of
the regex) would be
[ # \| \\ \| ` \| \( \$ \| @S|@ \) \( | \| { \| @{:@ \) ]
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