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Re: [perl #125471] sprintf behavior or documentation bug

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From:
Chas. Owens
Date:
June 24, 2015 13:47
Subject:
Re: [perl #125471] sprintf behavior or documentation bug
Message ID:
CAH2YjjGProzqLsvzmD=7=gxR=pt4L5Ga5EO20S3R1fwdo=otgw@mail.gmail.com
SUSv3 says "+ The result of a signed conversion shall always begin with a
sign ('+' or '-'). The conversion shall begin with a sign only when a
negative value is converted if this flag is not specified."

This tells me that our documentation incorrectly used the word positive as
the opposite of negative forgetting that 0 is neither.  Patch to correct
documentation follows.

diff --git a/pod/perlfunc.pod b/pod/perlfunc.pod
index 650ad0e..a781158 100644
--- a/pod/perlfunc.pod
+++ b/pod/perlfunc.pod
@@ -7244,10 +7244,15 @@ For example:
   printf '<%#B>',  12;   # prints "<0B1100>"

 When a space and a plus sign are given as the flags at once,
-a plus sign is used to prefix a positive number.
-
-  printf '<%+ d>', 12;   # prints "<+12>"
-  printf '<% +d>', 12;   # prints "<+12>"
+a plus sign is used to prefix a non-negative number in addition
+to the default prefixing of negative numbers.
+
+  printf '<%+ d>', -12; # prints "<-12>"
+  printf '<% +d>', -12; # prints "<-12>"
+  printf '<%+ d>', 0;   # prints "<+0>"
+  printf '<% +d>', 0;   # prints "<+0>"
+  printf '<%+ d>', 12;  # prints "<+12>"
+  printf '<% +d>', 12;  # prints "<+12>"

 When the # flag and a precision are given in the %o conversion,
 the precision is incremented if it's necessary for the leading "0".



On Tue, Jun 23, 2015 at 10:46 PM via RT <perlbug-followup@perl.org> wrote:

> # New Ticket Created by
> # Please include the string:  [perl #125471]
> # in the subject line of all future correspondence about this issue.
> # <URL: https://rt.perl.org/Ticket/Display.html?id=125471 >
>
>
> This is a bug report for perl from saint.snit@gmail.com,
> generated with the help of perlbug 1.40 running under perl 5.20.2.
>
> Hi,
>
> I've found a discrepancy between documentation and behavior.  I'm not
> sure which is correct.
>
> perldoc -f sprintf says, "When a space and a plus sign are given as
> the flags at once, a plus sign is used to prefix a positive number."
> This is not accurate.  As the documentation notes,
>
> printf '<%+ d>', 12;   # prints "<+12>"
>
> However, the plus sign is printed even in the case of one number that
> isn't positive:
>
> printf '<%+ d>', 0;   # prints "<+0>" instead of "<0>" or "< 0>"
>
> Is the documentation supposed to say "a plus sign is used to prefix a
> nonnegative number"?  Or is the combination of space and + supposed to
> inhibit the printing of a plus sign before a 0?  The latter makes more
> sense, since there seems to be no other way to inhibit the illogical
> "+0" output while retaining the + for positive numbers.  (Why isn't this
> simply the default for all uses of the + flag?)
>
> Thank you.
> ---
> Flags:
>     category=library
>     severity=low
> ---
> Site configuration information for perl 5.20.2:
>
> Configured by Gentoo at Mon Apr  6 15:25:39 CDT 2015.
>
> Summary of my perl5 (revision 5 version 20 subversion 2) configuration:
>
>   Platform:
>     osname=linux, osvers=3.12.13-gentoo-3.12.13-custom,
> archname=i686-linux
>     uname='linux evo 3.12.13-gentoo-3.12.13-custom #3 smp sat jul 12
> 18:05:24 cdt 2014 i686 intel(r) pentium(r) 4 cpu 1.70ghz genuineintel
> gnulinux '
>     config_args='-des -Duseshrplib -Darchname=i686-linux
> -Dcc=i686-pc-linux-gnu-gcc -Doptimize=-O2 -march=native -pipe
> -Dldflags=-Wl,-O1 -Wl,--as-needed -Dprefix=/usr -Dinstallprefix=/usr
> -Dsiteprefix=/usr/local -Dvendorprefix=/usr -Dscriptdir=/usr/bin
> -Dprivlib=/usr/lib/perl5/5.20.2 -Darchlib=/usr/lib/perl5/5.20.2/i686-linux
> -Dsitelib=/usr/local/lib/perl5/5.20.2
> -Dsitearch=/usr/local/lib/perl5/5.20.2/i686-linux
> -Dvendorlib=/usr/lib/perl5/vendor_perl/5.20.2
> -Dvendorarch=/usr/lib/perl5/vendor_perl/5.20.2/i686-linux
> -Dman1dir=/usr/share/man/man1 -Dman3dir=/usr/share/man/man3
> -Dsiteman1dir=/usr/local/man/man1 -Dsiteman3dir=/usr/local/man/man3
> -Dvendorman1dir=/usr/share/man/man1 -Dvendorman3dir=/usr/share/man/man3
> -Dman1ext=1 -Dman3ext=3pm -Dlibperl=libperl.so.5.20.2
> -Dlocincpth=/usr/include  -Dglibpth=/lib /usr/lib  -Duselargefiles
> -Dd_semctl_semun -Dcf_by=Gentoo -Dmyhostname=localhost
> -Dperladmin=root@localhost -Dinstallusrbinperl=n -Ud_csh -Uusenm -Di_ndbm
> -Di_gdbm -Di_db -DDEBUGGING=none -Dinc_version_list=5.20.0/i686-linux
> 5.20.0 5.20.1/i686-linux 5.20.1  -Dnoextensions=ODBM_File'
>     hint=recommended, useposix=true, d_sigaction=define
>     useithreads=undef, usemultiplicity=undef
>     use64bitint=undef, use64bitall=undef, uselongdouble=undef
>     usemymalloc=n, bincompat5005=undef
>   Compiler:
>     cc='i686-pc-linux-gnu-gcc', ccflags ='-fwrapv -fno-strict-aliasing
> -pipe -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
>     optimize='-O2 -march=native -pipe',
>     cppflags='-fwrapv -fno-strict-aliasing -pipe'
>     ccversion='', gccversion='4.8.3', 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='i686-pc-linux-gnu-gcc', ldflags ='-Wl,-O1 -Wl,--as-needed'
>     libpth=/usr/lib/gcc/i686-pc-linux-gnu/4.8.3/include-fixed /usr/lib
> /lib/../lib /usr/lib/../lib /lib
>     libs=-lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc -lgdbm_compat
>     perllibs=-lnsl -ldl -lm -lcrypt -lutil -lc
>     libc=libc-2.19.so, so=so, useshrplib=true, libperl=libperl.so.5.20.2
>     gnulibc_version='2.19'
>   Dynamic Linking:
>     dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
>     cccdlflags='-fPIC', lddlflags='-shared -O2 -march=native -pipe
> -Wl,-O1 -Wl,--as-needed'
>
> Locally applied patches:
>     gentoo/hints_hpux - Fix hpux hints
>     gentoo/aix_soname - aix gcc detection and shared library soname
> support
>     gentoo/EUMM-RUNPATH - https://bugs.gentoo.org/105054
> cpan/ExtUtils-MakeMaker
> <https://bugs.gentoo.org/105054cpan/ExtUtils-MakeMaker>: drop
> $PORTAGE_TMPDIR from LD_RUN_PATH
>     gentoo/config_over - Remove -rpath and append LDFLAGS to lddlflags
>     gentoo/opensolaris_headers - [PATCH] Add headers for opensolaris
>     gentoo/patchlevel - List packaged patches for perl-5.20.2(#1)
> in patchlevel.h
>     gentoo/cpanplus_definstalldirs - Configure CPANPLUS to use the site
> directories by default.
>     gentoo/cleanup-paths - [PATCH] Cleanup PATH and shrpenv
>     gentoo/enc2xs - Tweak enc2xs to follow symlinks and ignore missing
> @INC directories.
>     gentoo/enc2xs_checksums -
>     gentoo/darwin-cc-ld - https://bugs.gentoo.org/297751 [PATCH] darwin:
> Use $CC to link
>     gentoo/cpan_definstalldirs - Provide a sensible INSTALLDIRS default
> for modules installed from CPAN.
>     gentoo/interix - [PATCH] Fix interix hints
>     gentoo/create_libperl_soname - https://bugs.gentoo.org/286840 [PATCH]
> Set libperl soname
>     gentoo/mod_paths - Add /etc/perl to @INC
>     gentoo/EUMM_delete_packlist -
>     gentoo/drop_fstack_protector - https://bugs.gentoo.org/348557 [PATCH]
> Don't force -fstack-protector on everyone
>     gentoo/usr_local - [PATCH] Remove /usr/local paths
>     gentoo/D-SHA-CFLAGS - https://bugs.gentoo.org/506818 [PATCH] Do not
> set custom CFLAGS in cpan/Digest-SHA
>     gentoo/io_socket_ip_tests -
>     debian/cpan-missing-site-dirs - Fix CPAN::FirstTime defaults with
> nonexisting site dirs if a parent is writable
>     debian/regcomp-mips-optim - Downgrade the optimization of regcomp.c
> on mips and mipsel due to a gcc-4.9 bug
>     debian/perldoc-less-R - Tell the 'less' pager to allow terminal
> escape sequences
>     debian/makemaker-pasthru - Pass LD settings through to subdirectories
>     fixes/net_smtp_docs - [rt.cpan.org #36038] Document the Net::SMTP
> 'Port' option
>     fixes/memoize_storable_nstore - [rt.cpan.org #77790]
> Memoize::Storable: respect 'nstore' option not respected
>     fixes/document_makemaker_ccflags - [rt.cpan.org #68613] Document
> that CCFLAGS should include $Config{ccflags}
>
> ---
> @INC for perl 5.20.2:
>     /etc/perl
>     /usr/local/lib/perl5/5.20.2/i686-linux
>     /usr/local/lib/perl5/5.20.2
>     /usr/lib/perl5/vendor_perl/5.20.2/i686-linux
>     /usr/lib/perl5/vendor_perl/5.20.2
>     /usr/local/lib/perl5
>     /usr/lib/perl5/vendor_perl/5.20.1/i686-linux
>     /usr/lib/perl5/vendor_perl/5.20.1
>     /usr/lib/perl5/vendor_perl
>     /usr/lib/perl5/5.20.2/i686-linux
>     /usr/lib/perl5/5.20.2
>     .
>
> ---
> Environment for perl 5.20.2:
>     HOME=/home/vax
>     LANG=en_US
>     LANGUAGE (unset)
>     LC_COLLATE=C
>     LD_LIBRARY_PATH (unset)
>     LOGDIR (unset)
>
> PATH=/home/vax/bin:/usr/local/bin:/usr/bin:/bin:/opt/bin:/usr/i686-pc-linux-gnu/gcc-bin/4.7.3:/usr/games/bin:/sbin:/usr/sbin:/usr/games/bin:./bin
>     PERL_BADLANG (unset)
>     SHELL=/bin/bash
>
>

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