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[perl #51568] Scalar::Util::looks_like_number vs. Optimzation in regex?

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Steffen_Ullrich @ genua . de
March 10, 2008 08:39
[perl #51568] Scalar::Util::looks_like_number vs. Optimzation in regex?
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This is a bug report for perl from,
generated with the help of perlbug 1.35 running under perl v5.8.8.

[Please enter your report here]

looks like I've triggered a problem with a regex followed by a looks_like_number.
With the example program (below) I can trigger the problem on perl5.8.8 on Linux,
OpenBSD, and MacOSX and with perl5.10 on MacOSX (no other platforms tested).

If I use this example program the call of test1 on line 5 gives shows, that
looks_like_number gives false, while the same call in line 7 gives true.
If I slightly modify the call to have a temporary variable in the call of
looks_like_number it succeedes. 
Playing with the order of the calls of test1 and test2 I get:
- test2 (with the temp variable=) succeedes every time
- test1 fails if called as the first test
- test1 succeeds if called after a (successful) test2 or after a (failed) test1

Because a similar bug from me
was considered high I put this one as high too.

Steffen (cpan: SULLR)

     1	use strict;
     2	use warnings;
     3	use Scalar::Util 'looks_like_number';
     5	warn "test1: ",test1('duration>0.25'),"\n";
     6	warn "test2: ",test2('duration>0.25'),"\n";
     7	warn "test1: ",test1('duration>0.25'),"\n";
     8	warn "test2: ",test2('duration>0.25'),"\n";
    10	sub test1 {
    11	    my $x = shift;
    12	    if ( $x =~m{^(\w+)([<>])(\S+)$} ) {
    13		    if ( looks_like_number($3) ) {
    14			    return "looks like number $3";
    15		    } else {
    16			    return "no number $3";
    17		    }
    18	    } else {
    19		    return "no comparison";
    20	    }
    21	}
    23	sub test2 {
    24	    my $x = shift;
    25	    if ( $x =~m{^(\w+)([<>])(\S+)$} ) {
    26		    if ( looks_like_number(my $k = $3) ) {
    27			    return "looks like number $3";
    28		    } else {
    29			    return "no number $3";
    30		    }
    31	    } else {
    32		    return "no comparison";
    33	    }
    34	}

[Please do not change anything below this line]
Site configuration information for perl v5.8.8:

Configured by Debian Project at Mon Nov  5 06:19:33 UTC 2007.

Summary of my perl5 (revision 5 version 8 subversion 8) configuration:
    osname=linux, osvers=2.6.22-3-amd64, archname=i486-linux-gnu-thread-multi
    uname='linux deneb 2.6.22-3-amd64 #1 smp thu oct 11 15:23:23 utc 2007 i686 gnulinux '
    config_args='-Dusethreads -Duselargefiles -Dccflags=-DDEBIAN -Dcccdlflags=-fPIC -Darchname=i486-linux-gnu -Dprefix=/usr -Dprivlib=/usr/share/perl/5.8 -Darchlib=/usr/lib/perl/5.8 -Dvendorprefix=/usr -Dvendorlib=/usr/share/perl5 -Dvendorarch=/usr/lib/perl5 -Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl/5.8.8 -Dsitearch=/usr/local/lib/perl/5.8.8 -Dman1dir=/usr/share/man/man1 -Dman3dir=/usr/share/man/man3 -Dsiteman1dir=/usr/local/man/man1 -Dsiteman3dir=/usr/local/man/man3 -Dman1ext=1 -Dman3ext=3perl -Dpager=/usr/bin/sensible-pager -Uafs -Ud_csh -Uusesfio -Uusenm -Duseshrplib -Dd_dosuid -des'
    hint=recommended, useposix=true, d_sigaction=define
    usethreads=define use5005threads=undef useithreads=define usemultiplicity=define
    useperlio=define d_sfio=undef uselargefiles=define usesocks=undef
    use64bitint=undef use64bitall=undef uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
    cc='cc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -DTHREADS_HAVE_PIDS -DDEBIAN -fno-strict-aliasing -pipe -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -DTHREADS_HAVE_PIDS -DDEBIAN -fno-strict-aliasing -pipe -I/usr/local/include'
    ccversion='', gccversion='4.1.2 20061115 (prerelease) (Debian 4.1.1-21)', gccosandvers=''
    intsize=4, longsize=4, ptrsize=4, doublesize=8, byteorder=1234
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=12
    ivtype='long', ivsize=4, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=4, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib
    libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
    perllibs=-ldl -lm -lpthread -lc -lcrypt
    libc=/lib/, so=so, useshrplib=true,
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fPIC', lddlflags='-shared -L/usr/local/lib'

Locally applied patches:

@INC for perl v5.8.8:

Environment for perl v5.8.8:
    LANG (unset)
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PERL_BADLANG (unset)

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