Non-canonical hexadecimal floats are parsed prematurely

[p5pRT]

Migrated from rt.perl.org#127183 (status was 'resolved')

Searchable as RT127183$

[p5pRT]

From dankogai@dan.co.jp

Created by dankogai@dan-imac151.local

I am so glad Perl 5.22 adds support to the C99 hexadecimal floating point notation. What I am not so glad is I found that perl sometimes parses hex floats prematurely.

  % perl -E 'say sprintf "%a", 0x0.b17217f7d1cf78p0 - 0x1.62e42fefa39efp-1'
  -0x1p-53

As you see, LHS is non-normal form and RHS normal. AFAIK in other platforms that support hexfloats 0x0.b17217f7d1cf78p0 == 0x1.62e42fefa39efp-1​:

C​:
  http​://ideone.com/Q0kbTL
C++​:
  http​://ideone.com/j3odtE
Ruby​:
  http​://ideone.com/VPj3Ie
Swift​:
  http​://swiftlang.ng.bluemix.net/#/repl/2e2ccb20e8e262f8f54dc7e8af7fda9511f526198c1e71584bd17029616c3cf6

Dan the Bit-Picking Perl Monger

Perl Info

Flags:
    category=core
    severity=medium

Site configuration information for perl 5.22.1:

Configured by dankogai at Thu Dec 17 00:32:07 JST 2015.

Summary of my perl5 (revision 5 version 22 subversion 1) configuration:

  Platform:
    osname=darwin, osvers=15.2.0, archname=darwin-thread-multi-2level
    uname='darwin dan-imac151.local 15.2.0 darwin kernel version 15.2.0: fri nov 13 19:56:56 pst 2015; root:xnu-3248.20.55~2release_x86_64 x86_64 '
    config_args='-DDEBUGGING -Doptimize=-g -pipe -Os -Accflags=-DPERL_USE_SAFE_PUTENV -Duseshplib -Dusethreads -Dusemultiplicity -Duse64bitall -des'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    use64bitint=define, use64bitall=define, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-fno-common -DPERL_DARWIN -arch x86_64 -DPERL_USE_SAFE_PUTENV -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector-strong -I/opt/local/include',
    optimize='-g -pipe -Os',
    cppflags='-arch x86_64 -fno-common -DPERL_DARWIN -arch x86_64 -DPERL_USE_SAFE_PUTENV -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector-strong -I/opt/local/include'
    ccversion='', gccversion='4.2.1 Compatible Apple LLVM 7.0.2 (clang-700.1.81)', 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='env MACOSX_DEPLOYMENT_TARGET=10.3 cc -arch x86_64', ldflags =' -arch x86_64 -fstack-protector-strong -L/usr/local/lib -L/opt/local/lib'
    libpth=/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../lib/clang/7.0.2/lib /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib /usr/lib /usr/local/lib /opt/local/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=' -bundle -undefined dynamic_lookup -L/usr/local/lib -L/opt/local/lib -fstack-protector-strong'



@INC for perl 5.22.1:
    /usr/local/lib/perl5/site_perl/5.22.1/darwin-thread-multi-2level
    /usr/local/lib/perl5/site_perl/5.22.1
    /usr/local/lib/perl5/5.22.1/darwin-thread-multi-2level
    /usr/local/lib/perl5/5.22.1
    /usr/local/lib/perl5/site_perl/5.22.0/darwin-thread-multi-2level
    /usr/local/lib/perl5/site_perl/5.22.0
    /usr/local/lib/perl5/site_perl
    .


Environment for perl 5.22.1:
    DYLD_LIBRARY_PATH (unset)
    HOME=/Users/dankogai
    LANG=en_US.UTF-8
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/Users/dankogai/sbin:/Users/dankogai/bin:/Users/dankogai/.rakudobrew/bin:/Users/dankogai/node_modules/.bin:/usr/local/bin:/opt/local/sbin:/opt/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
    PERL_BADLANG (unset)
    SHELL=/bin/tcsh

[p5pRT]

From @sisyphus

-----Original Message-----
From​: Dan Kogai (via RT)
Sent​: Wednesday, January 06, 2016 10​:57 PM
To​: bugs-bitbucket@​rt.perl.org
Subject​: [perl #127183] Non-canonical hexadecimal floats are parsed
prematurely

This is a bug report for perl from dankogai@​dan-imac151.local,
generated with the help of perlbug 1.40 running under perl 5.22.1.

% perl -E 'say sprintf "%a", 0x0.b17217f7d1cf78p0 -
0x1.62e42fefa39efp-1'
-0x1p-53

Works fine for me on MS Windows, perl-5.22.0​:

C​:\>perl -E "say sprintf '%a', 0x0.b17217f7d1cf78p0 - 0x1.62e42fefa39efp-1"
0x0p+0

A regression ?

Cheers,
Rob

[p5pRT]

The RT System itself - Status changed from 'new' to 'open'

[p5pRT]

From @jhi

If you can, please test the bleadperl at

http​://perl5.git.perl.org/perl.git/commit/eba98284740b799def26803ebac340aaa8930437

Test the hexfp literals and the %a without mercy.

[p5pRT]

From @iabyn

On Thu, Jan 07, 2016 at 01​:42​:01PM +1100, sisyphus1@​optusnet.com.au wrote​:

-----Original Message----- From​: Dan Kogai (via RT)
Sent​: Wednesday, January 06, 2016 10​:57 PM
To​: bugs-bitbucket@​rt.perl.org
Subject​: [perl #127183] Non-canonical hexadecimal floats are parsed
prematurely

This is a bug report for perl from dankogai@​dan-imac151.local,
generated with the help of perlbug 1.40 running under perl 5.22.1.

% perl -E 'say sprintf "%a", 0x0.b17217f7d1cf78p0 -
0x1.62e42fefa39efp-1'
-0x1p-53

Works fine for me on MS Windows, perl-5.22.0​:

C​:\>perl -E "say sprintf '%a', 0x0.b17217f7d1cf78p0 - 0x1.62e42fefa39efp-1"
0x0p+0

A regression ?

the maint-5.22 branch now prints 0x0p+0, as well as perl-5.23.0 onwards.
So I think this ticket can be closed.

--
"But Sidley Park is already a picture, and a most amiable picture too.
The slopes are green and gentle. The trees are companionably grouped at
intervals that show them to advantage. The rill is a serpentine ribbon
unwound from the lake peaceably contained by meadows on which the right
amount of sheep are tastefully arranged." -- Lady Croom, "Arcadia"

[p5pRT]

@iabyn - Status changed from 'open' to 'resolved'