Module:
Description
During regex compilation, Perl v5.32 appears to be misidentifying a \K that occurs
after a nested set of lookaheads as being inside a lookahead, and therefore incorrectly
terminates compilation with:
\K not permitted in lookahead/lookbehind in regex
This is, for example, causing problems for the Regexp::Debugger module,
which injects small lookaheads into regexes to assist with its reporting of
their matching process.
The reported misbehaviour does not occur in Perl v5.30.0 and earlier
(presumably because they didn't prohibit \K inside lookaheads).
Steps to Reproduce
use v5.32.0;
qr/(?=(?=x)x)\K/;
Expected behavior
This regex should compile correctly. The \K is not inside a lookahead.
Perl configuration
Summary of my perl5 (revision 5 version 32 subversion 0) configuration:
Platform:
osname=darwin
osvers=18.7.0
archname=darwin-2level
uname='darwin daneel.local 18.7.0 darwin kernel version 18.7.0: mon apr 27 20:09:39 pdt 2020; root:xnu-4903.278.35~1release_x86_64 x86_64 '
config_args='-de -Dprefix=/Users/damian/perl5/perlbrew/perls/perl-5.32.0 -Aeval:scriptdir=/Users/damian/perl5/perlbrew/perls/perl-5.32.0/bin'
hint=recommended
useposix=true
d_sigaction=define
useithreads=undef
usemultiplicity=undef
use64bitint=define
use64bitall=define
uselongdouble=undef
usemymalloc=n
default_inc_excludes_dot=define
bincompat5005=undef
Compiler:
cc='cc'
ccflags ='-fno-common -DPERL_DARWIN -mmacosx-version-min=10.14 -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -DPERL_USE_SAFE_PUTENV'
optimize='-O3'
cppflags='-fno-common -DPERL_DARWIN -mmacosx-version-min=10.14 -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include'
ccversion=''
gccversion='4.2.1 Compatible Apple LLVM 11.0.0 (clang-1100.0.33.8)'
gccosandvers=''
intsize=4
longsize=8
ptrsize=8
doublesize=8
byteorder=12345678
doublekind=3
d_longlong=define
longlongsize=8
d_longdbl=define
longdblsize=16
longdblkind=3
ivtype='long'
ivsize=8
nvtype='double'
nvsize=8
Off_t='off_t'
lseeksize=8
alignbytes=8
prototype=define
Linker and Libraries:
ld='cc'
ldflags =' -mmacosx-version-min=10.14 -fstack-protector-strong -L/usr/local/lib'
libpth=/usr/local/lib /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/clang/11.0.0/lib /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/lib /usr/lib
libs=-lpthread -lgdbm -ldbm -ldl -lm -lutil -lc
perllibs=-lpthread -ldl -lm -lutil -lc
libc=
so=dylib
useshrplib=false
libperl=libperl.a
gnulibc_version=''
Dynamic Linking:
dlsrc=dl_dlopen.xs
dlext=bundle
d_dlsymun=undef
ccdlflags=' '
cccdlflags=' '
lddlflags=' -mmacosx-version-min=10.14 -bundle -undefined dynamic_lookup -L/usr/local/lib -fstack-protector-strong'
Characteristics of this binary (from libperl):
Compile-time options:
HAS_TIMES
PERLIO_LAYERS
PERL_COPY_ON_WRITE
PERL_DONT_CREATE_GVSV
PERL_MALLOC_WRAP
PERL_OP_PARENT
PERL_PRESERVE_IVUV
PERL_USE_SAFE_PUTENV
USE_64_BIT_ALL
USE_64_BIT_INT
USE_LARGE_FILES
USE_LOCALE
USE_LOCALE_COLLATE
USE_LOCALE_CTYPE
USE_LOCALE_NUMERIC
USE_LOCALE_TIME
USE_PERLIO
USE_PERL_ATOF
Built under darwin
Compiled at Jun 27 2020 22:49:58
%ENV:
PERL5LIB="./lib:/Users/damian/perl5/perlbrew/perls/perl-5.32.0/lib/perl5/darwin-thread-multi-2level/:/Users/damian/perl5/perlbrew/perls/perl-5.32.0/lib/perl5/darwin-2level/:/Users/damian/perl5/perlbrew/perls/perl-5.32.0/lib/perl5:/Users/damian/perl5/perlbrew/perls/perl-5.32.0/lib"
PERL6LIB="./lib6:/Users/damian/lib/perl6"
PERLBREW_CSHRC_VERSION="0.76"
PERLBREW_HOME="/Users/damian/.perlbrew"
PERLBREW_MANPATH="/Users/damian/perl5/perlbrew/perls/perl-5.32.0/man"
PERLBREW_PATH="/Users/damian/perl5/perlbrew/bin:/Users/damian/perl5/perlbrew/perls/perl-5.32.0/bin"
PERLBREW_PERL="perl-5.32.0"
PERLBREW_ROOT="/Users/damian/perl5/perlbrew"
PERLBREW_VERSION="0.76"
PERL_MB_OPT="--install_base /Users/damian/perl5/perlbrew/perls/perl-5.32.0/"
PERL_MM_OPT="INSTALL_BASE=/Users/damian/perl5/perlbrew/perls/perl-5.32.0/"
@INC:
./lib
/Users/damian/perl5/perlbrew/perls/perl-5.32.0/lib/perl5/darwin-thread-multi-2level/
/Users/damian/perl5/perlbrew/perls/perl-5.32.0/lib/perl5/darwin-2level/
/Users/damian/perl5/perlbrew/perls/perl-5.32.0/lib/perl5/darwin-2level
/Users/damian/perl5/perlbrew/perls/perl-5.32.0/lib/perl5
/Users/damian/perl5/perlbrew/perls/perl-5.32.0/lib/5.32.0/darwin-2level
/Users/damian/perl5/perlbrew/perls/perl-5.32.0/lib/5.32.0
/Users/damian/perl5/perlbrew/perls/perl-5.32.0/lib
/Users/damian/perl5/perlbrew/perls/perl-5.32.0/lib/site_perl/5.32.0/darwin-2level
/Users/damian/perl5/perlbrew/perls/perl-5.32.0/lib/site_perl/5.32.0
/Users/damian/perl5/perlbrew/perls/perl-5.32.0/lib/5.32.0/darwin-2level
/Users/damian/perl5/perlbrew/perls/perl-5.32.0/lib/5.32.0
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