Skip Menu |
Report information
Id: 128889
Status: resolved
Priority: 0/
Queue: perl5

Owner: Nobody
Requestors: zefram [at]

Operating System: Linux
PatchStatus: (no value)
Severity: low
Type: core
Perl Version: 5.24.0
Fixed In: (no value)

CC: zefram [...]
From: zefram [...]
Date: Wed, 10 Aug 2016 15:10:18 +0100
Subject: printf %a mishandles negative pseudo-precision
To: perlbug [...]
Download (untitled) / with headers
text/plain 4.3k
This is a bug report for perl from, 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 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, so=so, useshrplib=true, 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
RT-Send-CC: perl5-porters [...]
Marking resolved until proven otherwise.

This service is sponsored and maintained by Best Practical Solutions and runs on infrastructure.

For issues related to this RT instance (aka "perlbug"), please contact perlbug-admin at