| CC: | zefram [...] fysh.org |
| From: | zefram [...] fysh.org |
| Date: | Wed, 10 Aug 2016 15:10:18 +0100 |
| Subject: | printf %a mishandles negative pseudo-precision |
| To: | perlbug [...] perl.org |
This is a bug report for perl from zefram@fysh.org,
generated with the help of perlbug 1.40 running under perl 5.24.0.
-----------------------------------------------------------------
[Please describe your issue here]
$ perl -lwe 'printf "%.*a\n", -1, 1.03125'
0x1.p+0
The above output is incorrect: it should be "0x1.08p+0". %a is
generally handling a precision specified by ".*" and separate argument
OK, equivalent to how it handles a precision specified in the format
string. It exhibits [perl #128888] for a zero precision either way.
If a negative precision is specified, which can only be done via ".*",
this is meant to be equivalent to not specifying a precision at all
(per L<perldoc/sprintf>, printf(3), and the C standard). Not specifying
a precision for %a means that enough fractional digits must be emitted
to show the value exactly, and this does happen if the precision is not
specified at all:
$ perl -lwe 'printf "%a\n", 1.03125'
0x1.08p+0
The decimal %e, for which precision defaults to 6, handles a negative
precision correctly:
$ perl -lwe 'printf "%.*e\n", 1, 1.03125'
1.0e+00
$ perl -lwe 'printf "%.*e\n", -1, 1.03125'
1.031250e+00
$ perl -lwe 'printf "%e\n", 1.03125'
1.031250e+00
[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
category=core
severity=low
---
Site configuration information for perl 5.24.0:
Configured by zefram at Mon May 9 19:42:55 BST 2016.
Summary of my perl5 (revision 5 version 24 subversion 0) configuration:
Platform:
osname=linux, osvers=3.16.0-4-amd64, archname=x86_64-linux-thread-multi
uname='linux barba.rous.org 3.16.0-4-amd64 #1 smp debian 3.16.7-ckt11-1+deb8u6 (2015-11-09) x86_64 gnulinux '
config_args='-des -Dprefix=/home/zefram/usr/perl/perl_install/perl-5.24.0-i64-f52 -Duselargefiles -Dusethreads -Uafs -Ud_csh -Uusesfio -Uusenm -Duseshrplib -Dusedevel -Uversiononly -Ui_db'
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 ='-D_REENTRANT -D_GNU_SOURCE -fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=2',
optimize='-O2',
cppflags='-D_REENTRANT -D_GNU_SOURCE -fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include'
ccversion='', gccversion='4.9.2', 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='cc', ldflags =' -fstack-protector-strong -L/usr/local/lib'
libpth=/usr/local/lib /usr/lib/gcc/x86_64-linux-gnu/4.9/include-fixed /usr/include/x86_64-linux-gnu /usr/lib /lib/x86_64-linux-gnu /lib/../lib /usr/lib/x86_64-linux-gnu /usr/lib/../lib /lib
libs=-lpthread -lnsl -ldb -ldl -lm -lcrypt -lutil -lc
perllibs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
libc=libc-2.19.so, so=so, useshrplib=true, libperl=libperl.so
gnulibc_version='2.19'
Dynamic Linking:
dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E -Wl,-rpath,/home/zefram/usr/perl/perl_install/perl-5.24.0-i64-f52/lib/5.24.0/x86_64-linux-thread-multi/CORE'
cccdlflags='-fPIC', lddlflags='-shared -O2 -L/usr/local/lib -fstack-protector-strong'
---
@INC for perl 5.24.0:
/home/zefram/usr/perl/perl_install/perl-5.24.0-i64-f52/lib/site_perl/5.24.0/x86_64-linux-thread-multi
/home/zefram/usr/perl/perl_install/perl-5.24.0-i64-f52/lib/site_perl/5.24.0
/home/zefram/usr/perl/perl_install/perl-5.24.0-i64-f52/lib/5.24.0/x86_64-linux-thread-multi
/home/zefram/usr/perl/perl_install/perl-5.24.0-i64-f52/lib/5.24.0
.
---
Environment for perl 5.24.0:
HOME=/home/zefram
LANG (unset)
LANGUAGE (unset)
LD_LIBRARY_PATH (unset)
LOGDIR (unset)
PATH=/home/zefram/usr/perl/perl_install/perl-5.24.0-i64-f52/bin:/home/zefram/usr/perl/util:/home/zefram/pub/x86_64-unknown-linux-gnu/bin:/home/zefram/pub/common/bin:/usr/bin:/bin:/usr/local/bin:/usr/games
PERL_BADLANG (unset)
SHELL=/usr/bin/zsh