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Re: [ID 20010824.010] Alpha error writing exceptional math value

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From:
Nicholas Clark
Date:
August 26, 2001 04:53
Subject:
Re: [ID 20010824.010] Alpha error writing exceptional math value
Message ID:
20010826125300.E4950@plum.flirble.org
On Fri, Aug 24, 2001 at 05:00:44PM -0400, Andrew Dalke wrote:

Thanks for the very thorough report.

> There is a problem with Perl 5.005_03 and 5.6.1  when printing
> the IEEE 754 NaN exception value.
> 
> Here's the reproducible, with the first to show that non-exceptional
> values really do work.
> 
>  ===============
> [dalke@pw600a perl-5.6.1]$ ./perl -Ilib -e 'use POSIX; print acos(0.5), "\n"'
> 1.0471975511966
> [dalke@pw600a perl-5.6.1]$ ./perl -Ilib -e 'use POSIX; print acos(3.7), "\n"'
> Floating exception (core dumped)

I asked a friend to run
perl -we 'use POSIX; print acos(3.7), "\n"'

on an alpha running Debian GNU/Linux. He gets NaN rather than a core dump.
He suggests building with -mieee in the cflags, which is what Debian use.


>   Compiler:
>     cc='cc', ccflags ='-fno-strict-aliasing -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
>     optimize='-O2',
>     cppflags='-fno-strict-aliasing -I/usr/local/include'
>     ccversion='', gccversion='egcs-2.91.66 19990314/Linux (egcs-1.1.2 release)', gccosandvers=''
>     intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678
>     d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=8
>     ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
>     alignbytes=8, usemymalloc=n, prototype=define
>   Linker and Libraries:
>     ld='cc', ldflags =' -L/usr/local/lib'
>     libpth=/usr/local/lib /usr/shlib /lib /usr/lib
>     libs=-lnsl -lndbm -lgdbm -ldb -ldl -lm -lc -lposix -lcrypt -lutil
>     perllibs=-lnsl -ldl -lm -lc -lposix -lcrypt -lutil
>     libc=, so=so, useshrplib=false, libperl=libperl.a
>   Dynamic Linking:
>     dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-rdynamic'
>     cccdlflags='-fpic', lddlflags='-shared -L/usr/local/lib'

Debian's Alpha perl gives a -V of

Summary of my perl5 (revision 5.0 version 6 subversion 1) configuration:
  Platform:
    osname=linux, osvers=2.2.15, archname=alpha-linux
    uname='linux flatline 2.2.15 #8 smp fri jul 12 09:36:31 mst 2052 alpha unknown '
    config_args='-Dccflags=-DDEBIAN -mieee -Dcccdlflags=-fPIC -Darchname=alpha-linux -Dprefix=/usr -Dprivlib=/usr/share/perl/5.6.1 -Darchlib=/usr/lib/perl/5.6.1 -Dvendorprefix=/usr -Dvendorlib=/usr/share/perl5 -Dvendorarch=/usr/lib/perl5 -Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl/5.6.1 -Dsitearch=/usr/local/lib/perl/5.6.1 -Dman1dir=/usr/share/man/man1 -Dman3dir=/usr/share/man/man3 -Dman1ext=1 -Dman3ext=3perl -Dpager=/usr/bin/sensible-pager -Uafs -Ud_csh -Uusesfio -Dotherlibdirs=/usr/lib/perl5/5.6:/usr/lib/perl5/5.005 -Duseshrplib -Dlibperl=libperl.so.5.6.1 -Dd_dosuid -des'
    hint=recommended, useposix=true, d_sigaction=define
    usethreads=undef use5005threads=undef useithreads=undef usemultiplicity=undef
    useperlio=undef d_sfio=undef uselargefiles=define usesocks=undef
    use64bitint=define use64bitall=define uselongdouble=undef
  Compiler:
    cc='cc', ccflags ='-DDEBIAN -mieee -fno-strict-aliasing -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
    optimize='-O2',
    cppflags='-DDEBIAN -mieee -fno-strict-aliasing -I/usr/local/include'
    ccversion='', gccversion='2.95.4 20010604 (Debian prerelease)', gccosandvers=''
    intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=8
    ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=8, usemymalloc=n, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib
    libs=-lgdbm -ldbm -ldb -ldl -lm -lc -lcrypt
    perllibs=-ldl -lm -lc -lcrypt
    libc=, so=so, useshrplib=true, libperl=libperl.so.5.6.1
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-rdynamic'
    cccdlflags='-fPIC', lddlflags='-shared -L/usr/local/lib'


Characteristics of this binary (from libperl): 
  Compile-time options: USE_64_BIT_INT USE_64_BIT_ALL USE_LARGE_FILES
  Built under linux
  Compiled at Jun 24 2001 01:25:23
  @INC:
    /usr/local/lib/perl/5.6.1
    /usr/local/share/perl/5.6.1
    /usr/lib/perl5
    /usr/share/perl5
    /usr/lib/perl/5.6.1
    /usr/share/perl/5.6.1
    /usr/local/lib/site_perl
    /usr/lib/perl5/5.6/alpha-linux
    /usr/lib/perl5/5.6
    /usr/lib/perl5/5.005
    .


Is building with -mieee a sensible idea? If so, should it be on by
default on Alpha linux?

Nicholas Clark

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