perl整数运算给出浮点答案

Question

以下代码模仿实际的生产代码.双引号用作来自XML文件的实际数据,使用XML:Twig以下方法解析:

#!/usr/bin/perl

use strict;
use warnings;
use diagnostics;
use Devel::Peek;

my $linetotalinclusive = "8458.80" * 1_000_000;

$linetotalinclusive = $linetotalinclusive;

my $c = "7980.00" * 1_000_000;

my $data = $linetotalinclusive - $c;

print Dump $c;

print Dump $linetotalinclusive;

print "$linetotalinclusive - $c = $data \n";

给出以下结果:

SV = PVNV(0x22885f0) at 0x21984f8
  REFCNT = 1
  FLAGS = (PADMY,IOK,NOK,pIOK,pNOK)
  IV = 7980000000
  NV = 7980000000
  PV = 0
SV = PVNV(0x2288650) at 0x21984c8
  REFCNT = 1
  FLAGS = (PADMY,NOK,pIOK,pNOK)
  IV = 8458799999
  NV = 8458800000
  PV = 0

8458800000 - 7980000000 = 478799999.999999

在我的笔记本电脑和生产服务器上运行时.(以上是我的笔记本电脑)但是,当我在另一台生产机器上运行时,它工作正常. use integer;在上面的代码使它工作.但我无法对生产代码(轻松)这样做.所以,我想知道......

1. 为什么会发生这种情况.
2. 修复它的perl解释器缺少什么编译选项.

更多信息:这是来自破碎的机器:

This is perl 5, version 18, subversion 1 (v5.18.1) built for x86_64-linux-thread-multi
perl -MPOSIX -le 'print LONG_MAX'
9223372036854775807

perl -V:[in]vsize
ivsize='8';
nvsize='8';

这是来自工作的机器:

This is perl, v5.8.9 built for x86_64-linux-ld

perl -MPOSIX -le 'print LONG_MAX'
9223372036854775807

perl -V:[in]vsize
ivsize='8';
nvsize='16';

这给出了预期的答案:

Summary of my perl5 (revision 5 version 8 subversion 9) configuration:
  Platform:
    osname=linux, osvers=2.6.32-431.3.1.el6.x86_64, archname=x86_64-linux-ld
    uname='linux 553291-amon-sul2.firstb2b.net 2.6.32-431.3.1.el6.x86_64 #1 smp sat jan 4 02:04:49 est 2014 x86_64 x86_64 x86_64 gnulinux '
    config_args=''
    hint=recommended, useposix=true, d_sigaction=define
    usethreads=undef use5005threads=undef useithreads=undef usemultiplicity=undef
    useperlio=define d_sfio=undef uselargefiles=define usesocks=undef
    use64bitint=define use64bitall=define uselongdouble=define
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-fno-strict-aliasing -pipe -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I/usr/include/gdbm',
    optimize='-O2',
    cppflags='-fno-strict-aliasing -pipe -I/usr/local/include -I/usr/include/gdbm'
    ccversion='', gccversion='4.4.7 20120313 (Red Hat 4.4.7-4)', gccosandvers=''
    intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16
    ivtype='long', ivsize=8, nvtype='long double', nvsize=16, Off_t='off_t', lseeksize=8
    alignbytes=16, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib /lib64 /usr/lib64 /usr/local/lib64
    libs=-lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc
    perllibs=-lnsl -ldl -lm -lcrypt -lutil -lc
    libc=, so=so, useshrplib=false, libperl=libperl.a
    gnulibc_version='2.12'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fPIC', lddlflags='-shared -O2 -L/usr/local/lib'


Characteristics of this binary (from libperl): 
  Compile-time options: PERL_MALLOC_WRAP USE_64_BIT_ALL USE_64_BIT_INT
                        USE_FAST_STDIO USE_LARGE_FILES USE_LONG_DOUBLE
                        USE_PERLIO

这个没有:

Summary of my perl5 (revision 5 version 8 subversion 8) configuration:
  Platform:
    osname=linux, osvers=2.6.18-194.26.1.el5, archname=x86_64-linux-thread-multi
    uname='linux x86-002.build.bos.redhat.com 2.6.18-194.26.1.el5 #1 smp fri oct 29 14:21:16 edt 2010 x86_64 x86_64 x86_64 gnulinux '
    config_args='-des -Doptimize=-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -Dversion=5.8.8 -Dmyhostname=localhost -Dperladmin=root@localhost -Dcc=gcc -Dcf_by=Red Hat, Inc. -Dinstallprefix=/usr -Dprefix=/usr -Dlibpth=/usr/local/lib64 /lib64 /usr/lib64 -Dprivlib=/usr/lib/perl5/5.8.8 -Dsitelib=/usr/lib/perl5/site_perl/5.8.8 -Dvendorlib=/usr/lib/perl5/vendor_perl/5.8.8 -Darchlib=/usr/lib64/perl5/5.8.8/x86_64-linux-thread-multi -Dsitearch=/usr/lib64/perl5/site_perl/5.8.8/x86_64-linux-thread-multi -Dvendorarch=/usr/lib64/perl5/vendor_perl/5.8.8/x86_64-linux-thread-multi -Darchname=x86_64-linux-thread-multi -Dvendorprefix=/usr -Dsiteprefix=/usr -Duseshrplib -Dusethreads -Duseithreads -Duselargefiles -Dd_dosuid -Dd_semctl_semun -Di_db -Ui_ndbm -Di_gdbm -Di_shadow -Di_syslog -Dman3ext=3pm -Duseperlio -Dinstallusrbinperl=n -Ubincompat5005 -Uversiononly -Dpager=/usr/bin/less -isr -Dd_gethostent_r_proto -Ud_endhostent_r_proto -Ud_sethostent_r_proto -Ud_endprotoent_r_proto -Ud_setprotoent_r_proto -Ud_endservent_r_proto -Ud_setservent_r_proto -Dinc_version_list=5.8.7 5.8.6 5.8.5 -Dscriptdir=/usr/bin'
    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=define use64bitall=define uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='gcc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing -pipe -Wdeclaration-after-statement -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -I/usr/include/gdbm',
    optimize='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -fno-strict-aliasing -pipe -Wdeclaration-after-statement -I/usr/local/include -I/usr/include/gdbm'
    ccversion='', gccversion='4.1.2 20080704 (Red Hat 4.1.2-50)', gccosandvers=''
    intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16
    ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='gcc', ldflags =''
    libpth=/usr/local/lib64 /lib64 /usr/lib64
    libs=-lresolv -lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lpthread -lc
    perllibs=-lresolv -lnsl -ldl -lm -lcrypt -lutil -lpthread -lc
    libc=, so=so, useshrplib=true, libperl=libperl.so
    gnulibc_version='2.5'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E -Wl,-rpath,/usr/lib64/perl5/5.8.8/x86_64-linux-thread-multi/CORE'
    cccdlflags='-fPIC', lddlflags='-shared -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic'


Characteristics of this binary (from libperl): 
  Compile-time options: MULTIPLICITY PERL_IMPLICIT_CONTEXT
                        PERL_MALLOC_WRAP USE_64_BIT_ALL USE_64_BIT_INT
                        USE_ITHREADS USE_LARGE_FILES USE_PERLIO
                        USE_REENTRANT_API

Answer 1

那不是整数运算.两个方程都包含浮点数.

my $linetotalinclusive = "8458.80" * 1_000_000;
                         ^^^^^^^^^    
my $c = "7980.00" * 1_000_000;
        ^^^^^^^^^

有时Perl会变得聪明并注意到浮点数可以存储为整数,但是当有字符串转换时似乎有问题.

Dump 7980.00 + 1_000_000_000_000;
Dump "7980.00" + 1_000_000_000_000;

SV = IV(0x7fd55401c8e0) at 0x7fd55401c8f0
  REFCNT = 1
  FLAGS = (PADTMP,IOK,READONLY,pIOK)
  IV = 1000000007980
SV = NV(0x7fd553831200) at 0x7fd553844990
  REFCNT = 1
  FLAGS = (PADTMP,NOK,READONLY,pNOK)
  NV = 1000000007980

还有其他事情发生:不断折叠.如果表达式只包含常量,Perl通常会在编译时执行数学运算.如果您通过B :: Deparse运行代码,它从已编译的操作码重构代码,您会看到您的方程已转换为常量.

my $linetotalinclusive = 8458799999.9999990463;
my $c = 7980000000;

第一个遭遇浮点错误.第二个没有.